supporting consolidation, replication and up-scaling of … · 2014-02-06 · supporting...

Supporting consolidation, replication and up-scaling of sustainable wastewater

treatment and reuse technologies for India

Project supported by the European Commission within the 7th Framework Programme Grant Number 308672 and the Department for Science and

Technology, Government of India

Deliverable 1.1

Updated documentation of technologies

SARASWATI Deliverable 1.1

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Work package WP1 Update and refinement of documentation

Deliverable number D 1.1

Deliverable title Updated documentation of technologies

Due date Month 3

Actual submission date Month 16

Start date of project 01.09.2012

Participants EU (Partner short names) BRGM, BOKU, CEMDS

Participants India (Partner short names) IIT-R, IIT-Kgp, IIT-M, NITIE

Authors in alphabetical order

Dissemination level:

(PUblic, Restricted to other Programmes Participants, REstricted to a group specified by the consortium, COnfidential- only for members of the consortium)

L. Cary (BRGM), L. Essl (CEMDS), M. Ghangrekar (IIT-Kgp), A. Laurent (BRGM), A.A. Kazmi (IIT-R), L. Philips (IIT-M), A. Singh (NITIE), M. Starkl (BOKU)

PU

Deliverable Status: Version 1.0


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Contents 1 Introduction ...................................................................................................................... 12

2 Global overview of acquired data ................................................................................... 13

3 Description of technologies for combined wastewater treatment ............................... 17

3.1 WASTE STABILISATION PONDS (WSP) ..................................................................... 17 3.1.1 Brief description of technology ............................................................................. 17 3.1.2 Special features of technology ............................................................................. 17 3.1.3 Summary of distribution of technology across India ............................................. 17

3.2 KARNAL TECHNOLOGY (KT) ...................................................................................... 19 3.2.1 Brief description of technology ............................................................................. 19 3.2.2 Special features of technology ............................................................................. 19 3.2.3 Summary of distribution of technology across India ............................................. 20 3.2.4 Summary of experiences with technology performance across India ................... 20

3.3 ON-SITE PACKAGE: ANAEROBIC FILTER SYSTEM FOR INDIVIDUAL HOUSES (SINTEX, PWTS-AM, CCST, THST) ............................................................................. 21 3.3.1 Special features of technology ............................................................................. 21 3.3.2 Summary of distribution of technology across India ............................................. 21 3.3.3 Summary of experiences with technology performance across India ................... 21

3.4 DEWATS/BORDA ......................................................................................................... 22 3.4.1 Brief description of technology ............................................................................. 22 3.4.2 Special features of technology ............................................................................. 22 3.4.3 Summary of distribution of technology across India ............................................. 22 3.4.4 Summary of experiences with technology performance across India ................... 22

3.5 DEWATS OTHERS (ABR AND CW) ............................................................................. 23 3.5.1 Anaerobic baffled reactor (ABR) .......................................................................... 23 3.5.2 Constructed wetland ............................................................................................ 24

3.6 VORTEX SYSTEM ....................................................................................................... 25 3.6.1 Brief description of technology ............................................................................. 25 3.6.2 Special features of technology ............................................................................. 25 3.6.3 Summary of distribution of technology across India ............................................. 25 3.6.4 Summary of experiences with technology performance across India ................... 25

3.7 CONSTRUCTED SOIL FILTER, SOLID IMMOBILISED BIOFILTER, SOIL BIOTECHNOLOGY (SBT) ............................................................................................ 26 3.7.1 Brief description of technology ............................................................................. 26 3.7.2 Special features of technology ............................................................................. 26 3.7.3 Summary of distribution of technology across India ............................................. 26 3.7.4 Summary of experiences with technology performance across India ................... 26


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3.8 ANAEROBIC FILTER (AF) ............................................................................................ 27 3.8.1 Brief description of technology .............................................................................. 27 3.8.2 Special features of technology .............................................................................. 27 3.8.3 Summary of distribution of technology across India .............................................. 27 3.8.4 Summary of experiences with technology performance across India .................... 27

3.9 AERATED LAGOON ..................................................................................................... 28 3.9.1 Brief description of technology .............................................................................. 28 3.9.2 Special features of technology (if any) .................................................................. 28 3.9.3 Summary of distribution of technology across India .............................................. 28 3.9.4 Summary of experiences with technology performance across India .................... 28

3.10 UPFLOW ANAEROBIC SLUDGE BLANKET (UASB) ........................................... 29 3.10.1 Brief description of technology ......................................................................... 29 3.10.2 Special features of technology (if any) .............................................................. 29 3.10.3 Summary of distribution of technology across India .......................................... 29 3.10.4 Summary of experiences with technology performance across India ................ 29

3.11 ACTIVATED SLUDGE PACKAGE PLANT (ASP-PACKAGE) ............................... 31 3.11.1 Brief description of technology ......................................................................... 31 3.11.2 Special features of technology ......................................................................... 32 3.11.3 Summary of distribution of technology across India .......................................... 32 3.11.4 Summary of experiences with technology performance across India ................ 32

3.12 ACTIVATED SLUDGE PROCESS (ASP) ............................................................. 33 3.12.1 Brief description of technology ......................................................................... 33 3.12.2 Special features of technology ......................................................................... 33 3.12.3 Summary of distribution of technology across India .......................................... 33 3.12.4 Summary of experiences with technology performance across India ................ 34

3.13 EXTENDED AERATION (EA) ............................................................................... 36 3.13.1 Brief description of technology ......................................................................... 36 3.13.2 Special features of technology ......................................................................... 36 3.13.3 Summary of distribution of technology across India .......................................... 36 3.13.4 Summary of experiences with technology performance across India ................ 36

3.14 TRICKLING FILTER/BIOTOWER (TF/BT) ............................................................ 38 3.14.1 Brief description of technology ......................................................................... 38 3.14.2 Special features of technology ......................................................................... 38 3.14.3 Summary of distribution of technology across India .......................................... 38 3.14.4 Summary of experiences with technology performance across India ................ 38

3.15 CONTACT AERATION PACKAGE: SEWAGE TREATMENT SYSTEM SINTEX-NBF 40 3.15.1 Brief description of technology ......................................................................... 40 3.15.2 Special features of technology ......................................................................... 41 3.15.3 Summary of distribution of technology across India .......................................... 41 3.15.4 Summary of experiences with technology performance across India ................ 41


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3.16 ON-SITE AEROBIC PACKAGE: CONTACT AERATION SYSTEM FOR INDIVIDUAL HOUSES (STBF SERIES)........................................................................ 42 3.16.1 Special features of technology ......................................................................... 42 3.16.2 Summary of distribution of technology across India ......................................... 42 3.16.3 Summary of experiences with technology performance across India ............... 42

3.17 COMPACT WASTEWATER TREATMENT PLANTS (MMBR, FAB) .................... 43 3.17.1 Moving Bed Biofilm Reactor (MMBR)............................................................... 43 3.17.2 Fluidized Aerobic Bed (FAB) ........................................................................... 44

3.18 SUBMERGED AEROBIC FIXED FILM (SAFF) .................................................... 45 3.18.1 Brief description of technology ......................................................................... 45 3.18.2 Special features of technology ......................................................................... 45 3.18.3 Summary of distribution of technology across India ......................................... 45 3.18.4 Summary of experiences with technology performance across India ............... 45

3.19 MEMBRANE BIOREACTOR (MBR) .................................................................... 46 3.19.1 Brief description of technology ......................................................................... 46 3.19.2 Special features of technology ......................................................................... 46 3.19.3 Summary of distribution of technology across India ......................................... 46 3.19.4 Summary of experiences with technology performance across India ............... 46

3.20 SEQUENCING BATCH REACTOR (SBR) ........................................................... 47 3.20.1 Brief description of technology ......................................................................... 47 3.20.2 Special features of technology ......................................................................... 48 3.20.3 Summary of distribution of technology across India ......................................... 48 3.20.4 Summary of experiences with technology performance across India ............... 48

4 Description of technologies for black water treatment ................................................. 50

4.1 ANAEROBIC BAFFLED REACTOR .............................................................................. 50 4.1.1 Brief description of technology ............................................................................. 50 4.1.2 Special features of technology ............................................................................. 50 4.1.3 Summary of distribution of technology across India ............................................. 50 4.1.4 Summary of experiences with technology performance across India ................... 50

4.2 ANAEROBIC FILTER (AF) ............................................................................................ 51 4.2.1 Brief description of technology ............................................................................. 51 4.2.2 Special features of technology ............................................................................. 51 4.2.3 Summary of distribution of technology across India ............................................. 51 4.2.4 Summary of experiences with technology performance across India ................... 51

4.3 BIOGAS DIGESTER WITH OPTIONAL EFFLUENT TREATMENT .............................. 52

4.4 CONSTRUCTED WETLAND ........................................................................................ 52

5 Description of technologies for grey water treatment .................................................. 53

5.1 MULTIPLE STEP FILTRATION .................................................................................... 53 5.1.1 Brief description of technology ............................................................................. 53


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5.1.2 Special features of technology .............................................................................. 53 5.1.3 Summary of distribution of technology across India .............................................. 53 5.1.4 Summary of experiences with technology performance across India .................... 53

5.2 PLANTED FILTER ......................................................................................................... 55

5.3 BRIEF DESCRIPTION OF TECHNOLOGY ................................................................... 55 5.3.1 Special features of technology .............................................................................. 55 5.3.2 Summary of distribution of technology across India .............................................. 55 5.3.3 Summary of experiences with technology performance across India .................... 55

5.4 WASTE STABILISATION PONDS (WSP INCLUDING FLOATING WETLANDS) .......... 56 5.4.1 Floating aquatic plant systems (duckweed, water hyacinth) .................................. 56 5.4.2 Floating wetland (WSP) ........................................................................................ 58

5.5 EXTENDED AERATION (EA) ........................................................................................ 59 5.5.1 Brief description of technology .............................................................................. 59 5.5.2 Special features of technology .............................................................................. 59 5.5.3 Summary of distribution of technology across India .............................................. 59 5.5.4 Summary of experiences with technology performance across India .................... 59

5.6 GRAVEL FILTER ........................................................................................................... 61 5.6.1 Brief description of technology .............................................................................. 61 5.6.2 Special features of technology .............................................................................. 61 5.6.3 Summary of distribution of technology across India .............................................. 61 5.6.4 Summary of experiences with technology performance across India .................... 61

6 Discussion and conclusion ............................................................................................ 62

7 References ....................................................................................................................... 63


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List of tables

Table 1: Overview of surveyed wastewater treatment technologies in India .............................. 14

Table 2 : Number of wastewater treatment plants per State or Union Territory in India. ............ 15

Table 3: Results of one time sampling of WSPs ......................................................................... 18

Table 4: Results of one time sampling of anaerobic baffled reactor systems. ............................ 22

Table 5: Results of one time sampling of UASB with polishing pond. ........................................ 30 Table 6: Results of one time sampling of activated sludge systems. .......................................... 34

Table 7: Results of one time sampling of extended aeration systems. ....................................... 37

Table 8: Results of one time sampling of trickling filter. .............................................................. 39

Table 9: Results of one time sampling of FAB in Lucknow. ........................................................ 44

Table 10: Results of one time sampling of Anaerobic baffled reactor. ........................................ 50

Table 11: Results of one time sampling of the anaerobic filter in Delhi. ..................................... 51 Table 12: Results of sampling of extended aeration system in Madhya Pradesh, Tamilnadu and

Karnataka. .......................................................................................................... 60

Table 13: Results of sampling of extended aeration system in Indore. ...................................... 61

Table 14 : Number of sewage treatment plants per type of context. .......................................... 62


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List of figures

Figure 1: Location of the 1517 recorded wastewater treatment plants in the Indian States or Territories. .......................................................................................................... 16

Figure 2: Schematic layout of WSP system. ............................................................................... 17

Figure 3: Outline of Karnal technology (punenvis.nic.in/water/technologies3.htm)..................... 19

Figure 4: Data from CPCB (2005) and 8 MLD Haridwar STP based on Karnal Technology ...... 20 Figure 5: Typical cross-sectional drawings of septic-tank anaerobic filter (PWTS_AM) type systems

........................................................................................................................... 21

Figure 6: Schematic layout of DEWATS/BORDA system. .......................................................... 22

Figure 7: Schematic layout of an ABR system. ........................................................................... 23

Figure 8: Schematic layout of a constructed wetland. ................................................................. 24

Figure 9: Schematic layout of baffled reactor - vortex system – polishing pond system (Baetens et al., 2009). ........................................................................................................... 25

Figure 10: Schematic layout of earthworm technology systems. ................................................ 26

Figure 11: Schematic layout of an anaerobic filter system. ......................................................... 27

Figure 12: Schematic layout of an aerated lagoon system. ........................................................ 28

Figure 13: Schematic layout of UASB system. ............................................................................ 29 Figure 14: The three steps of the Wastewater treatment in NGPSTP. ....................................... 31

Figure 15: Schematic layout of activated sludge process system. .............................................. 33

Figure 16: Location of the recorded Activated Sludge process plants in India (109 recorded). .. 35

Figure 17: Schematic layout of Extended Aeration. .................................................................... 36

Figure 18: Schematic layout of a Trickling filter/Biotower system. .............................................. 38

Figure 19: Compact Aeration system .......................................................................................... 40 Figure 20: Schematic diagram of FMR. ....................................................................................... 43

Figure 21: Schematic layout of FAB type MBBR system. ........................................................... 44

Figure 22: Block diagram of MBR ................................................................................................ 46

Figure 23: Schematic layout of SBR system ............................................................................... 47

Figure 24: Schematic layout of SBR system. .............................................................................. 48

Figure 25: SBR treatment plants location in India (171 plants) in function of their total capacity.49 Figure 26: Schematic layout of biogas digester system .............................................................. 52

Figure 27: Schematic layout of multiple step filtration system..................................................... 53

Figure 28: Evaluation results (Source: Mooijman (2007) UNICEF). ........................................... 54

Figure 29: Schematic layout of planted filter system ................................................................... 55

Figure 30: Schematic layout of duckweed pond system ............................................................. 56

Figure 31: Location of duckweed ponds in Punjab. ..................................................................... 57 Figure 32: Schematic layout of floating wetland system (Source: Headley and Tanner, 2006). . 58

Figure 33: Schematic layout of the extended aeration system.................................................... 59

Figure 34: Schematic layout of the gravel filter system ............................................................... 61


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1 Introduction

This deliverable is the first of the project Saraswati. The project Saraswati aims at

- consolidating and disseminating the already available knowledge in India with respect to wastewater treatment technologies,

- assessing the sustainability and potential of already existing technologies in India for wastewater treatment

- assessing the potential of additional proven EU technologies for India, - and generating knowledge that can be used to replicate and up-scale the most

promising technologies for wastewater treatment and reuse in India, which will be an important step for solving grave water problems such as water scarcity and (river) water pollution.

The purpose of this deliverable is to provide an updated documentation of existing wastewater treatment and reuse technologies in India, on which the further work of SARASWATI can be based. This documentation thereby builds up on previous documentations conducted by the SARASWATI partners and on an up-to-date literature review. Indian partners have further contactedover 70 suppliers of wastewater treatment technologies as well as governmental institutions at different levels for providing information on existing wastewater treatment plants across India.

The documentation focuses on technologies for combined wastewater, however, also some technologies for black-water (water from toilet) and grey-water (water from kitchen and bath) treatment have been documented.

This documentation is structured in the following way: - Chapter 2 provides an overview of the identified technologies across India with some

basic information on their location and approximate numbers; - Chapter 3 provides a brief description of the different technology types for combined

wastewater treatment and a summary of the main results on performance data that could be collected from secondary sources;

- Chapter 4 provides a brief description of the different technology types for black water treatment;

- Chapter 5 provides a brief description of the different technology types for grey water treatment;

The documentation is concluded by a brief discussion and a conclusion section (Chapter 6).


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2 Global overview of acquired data

Up to now, 1517 plants could be documented (all data have been entered into an MS EXCEL and an MS ACCESS database). Municipal, institutional and residential wastewater treatment plants have been surveyed. Whereas municipal plants have been better documented by the consulted sources, residential and institutional plants are not so well documented and the collected information was mainly provided by the suppliers of wastewater treatment plants. Therefore, it can be assumed that by far not all existing residential and institutional plants could be documented.

An overview of existing wastewater treatment plants (WWTP) and reuse technologies across India resulting from the up-to-date bibliographic review and data collection from local sources is provided in Table 1. The surveyed technologies have been structured into four groups, with the availability of land and space as the determining factors.

Group 1 covers technologies that predominately occur in rural areas with vast and cheap land availability. It encompasses natural treatment technologies such as waste stabilization ponds and settling/anaerobic systems. It also includes package septic tank and its modifications for unsewered urban and peri-urban areas. Group 2 covers technologies that still require substantial land, but less than those of group 1, and includes technologies such as widely applied DEWATS systems. Group 3 encompasses intensive technologies which require much less space than those of groups 1 and 2, such as activated sludge based technologies. Finally, group 4 encompasses advanced technologies that require little space and are capable of achieving high effluent quality, such as membrane bioreactors.

A map showing all the plants, grouped into different categories of plant capacities that were recorded in the database, is presented in Figure 1. The map shows strong regional disparities. The number of plants per State or Union territory is given inTable 2. The States that present most recorded plants are Tamil Nadu (almost 21 % of the total) and Maharashtra (almost 18 %). Karnataka presents 8.6 % and Uttar Pradesh 6.5 % of the total number of plants. The other States present less than 100 plants.


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Table 1: Overview of surveyed wastewater treatment technologies in India

Type of Technology Short name Number of plants in India %

Rural Areas with cheaper land availability and on-site package septic systems for all areas

1 Waste stabilization ponds/Duckweed Pond/Water Hyacinth Pond WSP 136 9

2 Karnal technology KT 5 0.3

3 Onsite package (PWTS-AM series, THST series, CCST series) On-Site- Package 402 26.5

Rural Areas and peri-urban areas with cheaper limited space

4 DEWATS/BORDA DEWATS/BORDA 45 3

5 DEWATS Others DEWATS Others 53 3.5

6 VORTEX System VORTEX 2 0.1

7 Soil Bio Technology SBT 34 2.2

8 Anaerobic Filter AF 33 2.2

9 Aerated Lagoon AL 24 1.6

10 UASB UASB 53 3.5

Peri-Urban areas with expensive and limited space

11 New GPT- ASP Type- Ion Exchange India Ltd EA-Package 58 3.8

12 Conventional Activated sludge process ASP 109 7.2

13 Extended aeration EA 46 3 14 Trickling Filter TF/BT 16 1.1

15 NBF (10 KLD to 150 KLD) Contact Aeration-Package 79 5.2

16 Settler + Contact aeration (STBF series) On-site Aerobic- Package 42 2.8

Peri-Urban areas with expensive and limited space and strict effluent quality

17 Moving bed biofilm reactor (including FAB) MBBR 150 9.9 18 Submerged Aerobic Fixed film SAFF process SAFF 1 0.1

19 Membrane Bioreactor MBR 5 0.3

20 Sequencing Batch Reactor SBR 171 11.3 Unknown 53 3.5

Total 1517 100


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Table 2 : Number of wastewater treatment plants per State or Union Territory in India.

States/Union territories unknown Institutional Municipal Residential Total

Eastern India 11 11 68 5 95

Arunachal Pradesh 3 3 Bihar 5 10 15

Chhattisgarh 2 7 2 11

Meghalaya 2 3 5

Orissa 1 2 4 7 West Bengal 3 4 47 54

North Eastern India 3 4 2 9

Assam 2 3 5 Mizoram 1 1 Tripura 1 2 3

Northern India 231 65 113 18 427

Chandigarh 2 4 1 7 Delhi 37 16 31 6 90

Haryana 44 1 18 5 68 Himachal Pradesh 10 10 Jammu & Kashmir 9 4 13

Punjab 67 4 12 83 Rajasthan 18 10 2 30

Uttar Pradesh 42 21 30 5 98 Uttarakhand 14 7 6 1 28

Southern India 403 60 72 24 559

Andhra Pradesh 34 8 7 8 57

Karnataka 53 22 39 7 121

Kerala 42 4 5 1 52

Pondicherry 5 3 1 9

Tamil Nadu 269 23 20 8 320

Western India 213 32 163 19 427

Dadra & Nagar Haveli 1 1

Goa 5 1 2 8 Gujarat 60 10 24 1 95

Madhya Pradesh 24 8 19 51 Maharashtra 123 13 118 18 272

Total général 861 172 416 68 1517


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Figure 1: Location of the 1517 recorded wastewater treatment plants in the Indian States or Territories.


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3 Description of technologies for combined wastewater treatment

The following section presents a description of the technologies that are used for treating combined wastewater. The sequence of presented technologies follows the structure of Table 1 in the previous section.

3.1 WASTE STABILISATION PONDS (WSP)

3.1.1 Brief description of technology

Waste Stabilization Ponds (WSPs) are large, man-made water bodies. WSPs can be used individually, but usually they are combined in a series of three or more ponds: first an anaerobic; then a facultative pond and finally an aerobic or maturation pond (Tilley et al., 2008). The effluent contains nutrients and can be reused in agriculture or aquaculture.

A typical configuration of an UASB reactor as applied in India is shown in Figure 2.

Anaerobic pond

Facultative pond

Maturation pondSewage Pre-treatment

unit

Discharge to water body or irrigation/gardening/

aquaculture

Figure 2: Schematic layout of WSP system.

3.1.2 Special features of technology

WSP are especially suitable for rural areas where large unused lands, away from homes and public spaces are available. Waste stabilization ponds may be combined with aquaculture systems (duckweed,water hyacinth or fish production), (WSP, 2008) or used as polishing treatment of effluent from UASB systems.

3.1.3 Summary of distribution of technology across India

Waste stabilization ponds are one of the most commonly used treatment technology and 136 plants have been implemented all over India.

3.1.3.1 Summary of experiences with technology performance across India

The Central Pollution Control Board (CPCB 2005) conducted one time testing of basic parameters (BOD, COD, TSS, faecal coliforms) of 20 WSP systems. It can be seen in Table 3 that the concentration of BOD and COD is for all except of one treatment plant within the prescribed Indian standard for discharge into surface water; whereas 25 % of the systems do not comply with the Indian standard of 100 mg/l TSS. Faecal coliform counts are below 104

MPN/100 ml for 25% of the systems.


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Table 3: Results of one time sampling of WSPs

BOD (mg/l), 20 samples of final effluent

COD (mg/l), 20 samples of final effluent

TSS (mg/l), 20 samples of final effluent

Faecal coliforms (MPN/100ml), 19 samples of final effluent

Range within range Range within

range Range within range Range within

range

0-30 12 0-100 8 0-50 4 < 104 5

31-100 7 101 – 250 12 51-100 11 104 – 105 4

>100 1 >250 0 >100 5 >105 10

Standard for

discharge to surface

water

30 Standard for discharge to surface water


100 Standard for discharge to

surface water

no standar

d


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3.2 KARNAL TECHNOLOGY (KT)


The ENVIS (Environmental Information System) Centre Punjab sponsored by the Ministry of Environment and Forests, GOI and hosted by the Punjab State Council for Science and Technology describes this technology as follows (punenvis.nic.in/water/technologies3.htm):

The Karnal Technology involves growing trees on ridges 1m wide and 50cm high and disposing of the untreated sewage in furrows (see Figure 3). The amount of the sewage/ effluents to be disposed off depends upon the age, type of plants, climatic conditions, soil texture and quality of effluents. The total discharge of effluent is regulated in such a way that it is consumedwithin 12-18 hours and there is no standing water left in the trenches. Through this technique, it is possible to dispose off 0.3 to 1.0 ML of effluent per day per hectare. This technique utilizes the entire biomass as living filter for supplying nutrients to soil and plant; irrigation renovates the effluent for atmospheric re-charge and ground storage. Further, as forest plants are to be used for fuel wood, timber or pulp, there is no chance of pathogens, heavy metals and organic compounds to enter into the human food chain system, a point that is a limiting factor when vegetables or other crops are grown with sewage.

Figure 3: Outline of Karnal technology (punenvis.nic.in/water/technologies3.htm)

Though most of the plants are suitable for utilizing the effluents, yet, those tree species which are fast growing can transpire high amounts of water and are able to withstand high moisture content in the root environment, are most suitable for such purposes. Eucalyptus is one such species, which has the capacity to transpire large amounts of water, and remains active throughout the year.


This technology for sewage water use is relatively cheap and no major capital is involved. The expenditure of adopting this technology involves cost of making ridges, cost of plantation and their care.

This system generates gross returns from the sale of fuel wood. The sludge accumulating in the furrows along with the decaying forest litter can be exploited as an additional source of revenue. As the sewage water itself provides nutrients and irrigation ameliorates the sodic soil by lowering the pH, relatively unfertile wastelands can be used for this purpose. This technology is economically viable as it involves only the cost of water conveyance from source to fields for irrigation and does not require highly skilled personnel as well. This technology seems to be


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most appropriate and economical viable proposition for the rural areas as this technology is used to raise forestry, which would aid in re-storing environment and to generate biomass.


Five systems have been documented in Madhya Pradesh, 1 in Uttar Pradesh and 1 in Uttarakhand (CPCB, 2005 and Figure 4):

Location Total capacity

Ujjain (MP) 3.46 MLD

Vidhisha (MP) 9.0 MLD

Nagda (MP) 9.0 MLD

Chapara (MP) 1.2 MLD

Keolari (MP) 0.75 MLD

Bijnore (UP) 1.13 MLD

Haridwar (UK) 8.0 MLD

Figure 4: Data from CPCB (2005) and 8 MLD Haridwar STP based on Karnal Technology

3.2.4 Summary of experiences with technology performance across India

This technology has been adopted by Public Health Engineering Department (PHED) of M.P. State in Ujjain for disposal of around 50% of city sewage under one of the NRCD Projects to clean river Kshipra. A total of 24000 Eucalyptus trees were planted on 12 hectare of land in 1992. The scheme required regular application of city sewage. At Ujjain, the city sewage has been applied continuously throughout the year except for rainy season between June 01 and September 30. During the study, the sewage was first applied on November 01 after rainy season instead of October 01. The plants have grown to an optimum height and ready for harvesting. More information can be found in http://cpcbenvis.nic.in/ar2000/annual_report1999-2000-xxviii.htm

http://cpcbenvis.nic.in/ar2000/annual_report1999-2000-xxviii.htm

http://cpcbenvis.nic.in/ar2000/annual_report1999-2000-xxviii.htm


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3.3 ON-SITE PACKAGE: ANAEROBIC FILTER SYSTEM FOR INDIVIDUAL HOUSES (SINTEX, PWTS-AM, CCST, THST)

This type of package on-site treatment system consists of one or two chambers; it can be both settling or, settling and anaerobic filter (Figure 5). In settling and anaerobic filter type system, the first chamber works as a septic tank, where settleable solids are settled down and further degraded anaerobically at the bottom zone. The second chamber consists of upflow anaerobic filter where further removal of organic matter takes place. Anaerobic filters are made up of Pall ring (polypropylene) media with specific surface area of100 m2/m3. The high specific surface area not only prevents clogging but also provides intensive contact between the wastewater and the fixed film anaerobic bacteria for the fast degradation of organic matter. The treatment performance ranges 70-85 % for BOD and SS removal.

Figure 5: Typical cross-sectional drawings of septic-tank anaerobic filter (PWTS_AM) type systems


PWTS-AM type of package on-site treatment system is made up of LLDPE (Low Linear Density Polyethylene) and can be installed easily in a very short time. There is no energy consumption and BOD removal efficiency would be 25-50 % higher than conventional septic tanks.


About 636 plants have been implemented all over India for individual houses.


As per studies of IIT Roorkee, the system is found to remove more than 60% BOD, COD & TSS.


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3.4 DEWATS/BORDA


DEWATS is a trademark of the Bremen Overseas Research and Development Agency (BORDA) and stands for decentralized wastewater treatment system. A BORDA type DEWATS system usually consists of the following components: A settler, an ABR (anaerobic baffle reactor), and a planted gravel filter.

Figure 6: Schematic layout of DEWATS/BORDA system.


The technology is considered as suitable in areas with low capacity for operation and maintenance.


Forty five treatment plants applying BORDA type DEWATS technology could be identified (not including industrial plants) in India.


CDD India1 provides information about the performance of selected ABR systems. The evaluated ABRs are combined with biogas settlers and/or plated gravel filters. Table 4 summarizes the results. There seem to be some problems with removal of suspended solids, but the reasons for the concentrations above 100 mg/l are not further outlined. No independent evaluation results could be found. Table 4: Results of one time sampling of anaerobic baffled reactor systems.

BOD (mg/l), 16 samples of final

effluent

COD (mg/l), 16 samples of final

effluent

TSS (mg/l), 16 samples of final

effluent

Faecal coliforms (CFU/100ml),

7 samples of final effluent



range 0-30 13 0-100 15 0-50 9 < 104 7

31-100 3 101 – 250 1 51-100 1 104 – 105 0

>100 0 >250 0 >100 4

>105 0 > 200 2 Standard for discharge to surface water


surface water 250

Standard for discharge to

surface water 100

WHO guideline for unrestricted

irrigation

103

MPN/100ml Standard for

irrigation 100 Standard for irrigation - Standard for

irrigation 200

1www.cddindia.org


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3.5 DEWATS OTHERS (ABR AND CW)

Apart from BORDA type DEWATS, several other organizations have implemented similar type of decentralized wastewater treatment technologies with some variations. They are briefly described in the following sub-sections:

3.5.1 Anaerobic baffled reactor (ABR)

3.5.1.1 Brief description of technology

Anaerobic baffled reactors (ABR) (also called baffled reactors or baffled septic tanks) consist of a tank and alternating hanging and standing baffles that separate the reactor and force the water to flow up and down (Foxon et al 2004). The increased contact time with the active biomass (sludge) results in improved treatment. The majority of settleable solids are removed in the sedimentation chamber which is the first compartment of the ABR(Tilley et al. 2008).

ABRs are often combined with anaerobic filters to increase treatment efficiency. A further aerobic treatment of the effluent in reed bed or maturation ponds is necessary to increase dissolved oxygen level before releasing it into surface water or using it for irrigation (WSP 2008).

A typical configuration of an ABR as applied in India is shown in Figure 7.

Planted reed beds

Anaerobic filter

Discharge to water body or irrigation/gardeningSewage ABR

Figure 7: Schematic layout of an ABR system.

3.5.1.2 Special features of technology

The ABR is suitable for all types of wastewater, but its efficiency increases with higher organic loadings and is therefore most appropriate for the treatment of blackwater (WSP 2008). It requires no electricity and is stable to hydraulic shock loads.

As outlined above, ABRs are usually one part of a wastewater treatment system consisting of further anaerobic and aerobic treatment steps. Reuse of treated water for gardening or irrigation has been reported for the majority of the systems in India.

3.5.1.3 Summary of distribution of technology across India

ABR systems can be found all over India, but the majority of the documented systems (7) is located in Karnataka, Maharashtra and Uttar Pradesh.


Little documentation of the performance of those plants is available.


24

3.5.2 Constructed wetland


Constructed wetlands (also called reed beds or planted gravel filters) are natural treatment systems that consist of a bottom-lined bed or channel filled with appropriate soil media. A combination of physical settlement, photosynthesis, uptake by plants, degradation by bacteria in the root-zone and filtration are the main processes that improve wastewater quality (WSP 2009). Any plant with deep, wide roots that can grow in the wet, nutrient-rich environment is appropriate; phragmitesaustralis is a common choice (Tilley et al. 2008) Water is flowing above or below the surface (sub-surface flow). Flow direction in the filter bed maybe horizontal or vertical. Pre-treatment is required to prevent clogging of the bed media.

In India, sub-surface horizontal flow constructed wetlands are the most commonly applied type. A typical configuration is shown in Figure 8.

Horizontal flow constructed wetlandSewage Pre-treatment

unitDischarge to water body or irrigation/gardening

Figure 8: Schematic layout of a constructed wetland.

3.5.2.2 Special features of technology (if any)

Constructed wetlands provide secondary and tertiary treatment and can treat a wide range of wastewaters. They are often combined as advanced treatment with other, often anaerobic, treatment technologies such as ABR or anaerobic filters.


There are 6 examples of constructed wetland as secondary treatment in Madhya Pradesh, Punjab, Kerala and Delhi. In many systems all over India, constructed wetlands are used as advanced treatment of effluent of ABRs or anaerobic filters.


One constructed wetland located in Bhopal, Madhya Pradesh, was evaluated after its implementation in 2003 by Vipat et al. (2008). The effluent concentrations of BOD and COD were 20-34 mg/l and 32-75 mg/l, respectively. Average reduction of E.Coli was above 98% and 8x103 MPN/100ml in the effluent.


25

3.6 VORTEX SYSTEM


Vortex systems are tertiary treatment systems that are implemented in combination with baffled reactors, anaerobic filters and polishing ponds (Figure 9). A vortex system consists of a vertically positioned tube with a funnel shaped bottom element that serves as an opening to release the circulating effluent. The inlet is located at a tangent, being positioned either at the lower or the higher side of the tube (Baetens et al., 2009).

Figure 9: Schematic layout of baffled reactor - vortex system – polishing pond system (Baetens et al., 2009).


The technology replaces the commonly used planted filters and requires less space which makes an implementation in urban setting feasible. It requires electricity for operation.


The majority of the systems are located in Auroville, Tamil Nadu. Few applications in Karnataka and Maharashtra are documented.


With the inclusion of a vortex system, the natural treatment system is able to achieve a pollution reduction of 95% (Baetens et al., 2009). No detailed performance data are available.


26

3.7 CONSTRUCTED SOIL FILTER, SOLID IMMOBILISED BIOFILTER, SOIL BIOTECHNOLOGY (SBT)


The earthworm technology systems (called constructed soil filter, solid immobilised biofilter, or soil biotechnology) for wastewater treatment consist of a bed of suitable mineral constitution, culture containing native microflora, geophagus worms and is planted with e.g. canna.

Wastewater is passing the filter bed in vertical flow and can be redistributed if required. Optionally, a sand and/or carbon filter can be used as post-treatment. Effluent can be reused for e.g. gardening or irrigation.

A typical configuration of earthworm technology based wastewater treatment systems as applied in India is shown in Figure 10.

Soil filter with earthworms

(Sand filter)Sewage Collection

tankReuse of treated

wastewater Figure 10: Schematic layout of earthworm technology systems.


This technology is known under different names as it is protected by patent and offered by different companies.


The majority of implemented systems (34) is located in Maharashtra (31), some systems are located in Uttar Pradesh, Karnataka, Madhya Pradesh and Andhra Pradesh.


The technical performance of three earthworm based wastewater treatment systems located in Mumbai has been evaluated by Kadam (2007). Removal efficiencies were between 87-94% BOD and effluent concentrations were between 8.3-18.2 mg/l. Average log removal of faecal coliforms for all three sites was 2.2–3.4 and effluent concentrations were 3.1–8.3×104 CFU/100ml.


27

3.8 ANAEROBIC FILTER (AF)


An anaerobic filter (also known as fixed-bed or fixed-film reactor) consists of a sedimentation tank or septic tank followed by one to three filter chambers. Commonly used filter material includes gravel, crushed rocks, cinder and specially formed plastic pieces (Tilley et al. 2008). By forcing the wastewater to pass the filter, it gets into contact with active microorganisms growing on the filter material. Anaerobic filters may be operated as down-flow, up-flow or combined systems (Ulrich et al. 2009). Pre-treatment in settlers and septic tanks may be required to minimise the risk of clogging. Anaerobic filters are often combined with ABRs (see 3.4) and constructed wetlands (see 3.5.2).

A typical configuration of anaerobic filters as applied in India is shown in Figure 11.

Anaerobic filter

Planted gravel filterSewage Settler or

ABRDischarge to water body or irrigation/gardening

Figure 11: Schematic layout of an anaerobic filter system.


This technology is easily adaptable and can be applied at the household level or a small neighborhood if constant water flow is ensured. Depending on land availability and the hydraulic gradient of the sewer, an anaerobic filter can also be built underground(Tilley et al. 2008).


33 systems are documented, where anaerobic filters are the main treatment unit. They are located in Uttar Pradesh, Tamil Nadu, Delhi, Pondicherry, Maharashtra and Karnataka.


Little performance data are available.


28

3.9 AERATED LAGOON


Aerated lagoons (or aerated ponds) are similar to waste stabilisation ponds (see 3.1), but in addition mechanical aerators provide oxygen and keep the aerobic organisms suspended which allows for increased pond depth (Tilley et al. 2008).

There are two types of aerated lagoons: common aerated lagoons are enhanced facultative ponds, in which aerators are placed on the surface of the water, while completely mixed aerated ponds are in essence activated sludge systems without sludge. Effluent of completely mixed systems requires a post-treatment (e.g. in a sedimentation pond) as the sludge remains in suspension (Sustainable Sanitation and Water Management2). A typical configuration of an aerated lagoon as applied in India is shown in Figure 12.

Aerated lagoon (Sedimentation pond)Sewage Pre-treatment

unit Discharge to water body

Figure 12: Schematic layout of an aerated lagoon system.

3.9.2 Special features of technology (if any)

Compared to waste stabilisation ponds, space requirements are lower and the technology is also suited to colder climates. It is especially important that electricity service is uninterrupted and that replacement parts are available to prevent longer times without aeration that may cause anaerobic conditions in the pond (Tilley et al.2008).

Various combinations of aerated lagoons with other technologies (e.g UASB, duckweed pond, waste stabilisation ponds) depending on the requirements are possible (Arceivala and Asolekar 2008)


24 aerated lagoon systems for sewerage treatment are documented. The systems are located in Bihar, Maharashtra, Tamil Nadu and Karnataka.


Only for one system in Patna (Bihar) results for the performance are available (CPCB 2005). The aerated lagoon is combined with a fish pond. Removal rates of BOD, COD and TSS are 69%, 57% and 20%, respectively. However, as sewerage is of very low strength, the effluent achieves the required standard for discharge to streams. As for the plant in Karnataka, removal rates of BOD, COD and TSS are 90 %, 37.5 % and 75 %, respectively.

2www.sswm.info


29

3.10 UPFLOW ANAEROBIC SLUDGE BLANKET (UASB)


In an UASB reactor wastewater flows upwards through a blanket of flocculated biomass in a vertical reactor containing anaerobic bacteria which break down organic matter. The upward motion of gas bubbles produced during anaerobic digestion causes turbulence that enables mixing without mechanical assistance. Baffles at the top of the reactor allow gases to escape but prevent outflow of the sludge blanket (World Bank 2008).

UASBs only provide partial treatment and rarely meet discharge standards unless appropriate post-treatment is provided. Therefore, UASB reactors are usually combined with aerobic post-treatment systems (e.g waste stabilisation ponds).

A typical configuration of an UASB reactor as applied in India is shown in Figure 13.

Polishing pond(s)UASB Discharge to water bodySewage Pre-treatment

unit Figure 13: Schematic layout of UASB system.

3.10.2 Special features of technology (if any)

UASB reactors are especially well suited for high strength wastewater due to low energy consumption, production of biogas and low operation and maintenance costs.

The systems are particularly adapted for densely populated urban areas as they have low land requirements. However, if combined with polishing ponds as done in all identified systems in India, space requirements increase.


Within the Yamuna Action Plan (1993-2002) 16 UASB based wastewater treatment plants were implemented in Uttar Pradesh and Haryana with a capacity of more than 600 MLD. Subsequently, all over the country UASB systems were implemented and 53 documented sewage treatment plants were identified and recorded in the database.


The Central Pollution Control Board (CPCB 2005) conducted one time testing of basic parameters (BOD, COD, TSS, faecal coliforms) of 22 UASB systems with polishing ponds as post-treatment. It can be seen in Table 5 that the concentration of BOD is only for 22% of the evaluated systems within the prescribed Indian standard for discharge into surface water; whereas 77 % of the systems have effluent concentrations below the Indian standard of 250 mg/l COD and 86% fulfill the standard for TSS. Faecal coliform counts are above 105MPN/100 ml for the majority of the systems.


30

Table 5: Results of one time sampling of UASB with polishing pond.


effluent


effluent


effluent

Faecal coliforms (MPN/100ml),



range Range within range Range within range

0-30 5 0-100 6 0-50 15 < 104 1 31-100 13 101 – 250 11 51-100 4 104 – 105 3 >100 4 >250 5 >100 3 >105 11

Standard for


water

30

Standard for


water

250

Standard for


water

100

Standard for discharge to

surface water

no standard

One UASB system in Hyderabad with aerated lagoons and polishing pond as post-treatment was tested by an external lab and the one time sampling showed 85 % reduction of BOD and COD. Nitrate was reduced by 89% and Phosphorus by 66%.


31

3.11 ACTIVATED SLUDGE PACKAGE PLANT (ASP-PACKAGE)


New generation packaged sewage treatment plant (NGPSTP) is unique combination of lamella plate clarification and aeration that results in a ready - to - operate, prefabricated solution of outstanding performances and efficiency. This is the most compact "all in one" system available. The system is fully covered preventing noise and fly nuisance. It is also a modular unit that lends itself to future expansion or relocation. Wastewater treatment in NGPSTP takes place into three steps (Figure 14).

Figure 14: The three steps of the Wastewater treatment in NGPSTP.

Step 1: Primary settlement

Sewage initially enters the primary settlement tank. The tank incorporates lamella parallel plates which aid in reducing the suspended solids by 70% and the BOD by 25%. This zone is relatively maintenance free and contains no moving mechanical or electrical devices.

Step 2: Aerobic Treatment

The effluent then enters the aerator bio-zone, which is a combined fixed film reactor and active aeration system mounted on a horizontal shaft. The aerator provides a solid surface area for micro-organisms to attach themselves; these then feed on the organic matter present in the effluent. The rotation of the drum creates an aeration of the liquid. The bio-zone is self-cleansing and does not require extraneous pumping or sludge return.

Step 3: Final Settlement

The treated effluent then moves to the settlement area. This area contains a lamella parallel plate assembly for settling finer particles. The submersible pump removes sludge to the sludge storage compartment on a regular basis.


32


The packaged sewage treatment plant is all-in-one single tank, with a three-month sludge storage capacity.


About 58 systems are used in hotels, restaurants, holiday resorts, golf and country clubs, housing complexes, townships and national parks all over India.


There is no information available on its performance across India.


33

3.12 ACTIVATED SLUDGE PROCESS (ASP)


Activated sludge process is applied in reactor unit that makes use of mainly aerobic microorganisms to degrade organics in wastewater. To maintain aerobic conditions and to keep the active biomass suspended, a constant and well-timed supply of oxygen is required (Tilley et al. 2008)

Activated sludge reactors are only a part of a wastewater treatment system; additional components are a pre-treatment unit, a primary settling unit and a secondary clarifier to separate the biomass from the treated effluent and recirculate it to the activated sludge reactors. Sludge treatment of excess sludge is required. A typical configuration of a system using activated sludge process as applied in India is shown in Figure 15.

Aeration unit Secondary clarifierSewage Pre-treatment unit

(incl. primary clarifier)

Sludge treatment

circulation of sludge

Discharge to water body

Figure 15: Schematic layout of activated sludge process system.


Different versions of the original reactor configurations have been tested. The most common ones are plug-flow reactors and complete-mix reactors processes (Tchobanoglous1991). In plug-flow systems, the different aerobic and anaerobic stages correspond only to zones, while completely stirred processes require a single tank for each step.

Technologies that use the same removal process (aerobic biological treatment), but apply different designs are the extended aeration process (see 3.13), sequencing batch reactors (see 3.20), trickling filters (see 3.14).


Wastewater treatment plants using activated sludge process have been implemented all over India and 109 were documented in the database. In Delhi alone, 22 activated sludge treatment plants are installed.


34


A technical evaluation of 17 conventional activated sludge treatment plants in north India by Kazmi (2008) showed average removal of BOD, SS, TC and FC of 89%, 86%, log 2.1 and log 2.2, respectively (Table 6). Effluent concentrations were below 30mg/l BOD in 15 treatment plants. However, FC in the effluent were in none of the evaluated systems below log 4 MPN/100 ml which is above the value of log 3 MPN/100ml for unrestricted irrigation defined by the WHO (1989). An additional treatment step would be required to remove coliforms and make the water fit for irrigation.

Another evaluation of 22 conventional activated sludge treatment plants all over India3, showed that effluent complies in almost all treatment plants with the standard, but similar to the results obtained by Kazmi (2008), faecal coliform counts in the effluent were high above the 103 MPN/100ml in the WHO guidelines (1989).

Table 6: Results of one time sampling of activated sludge systems.


effluent


effluent TSS (mg/l, 22 samples

of final effluent


13samples of final effluent

Range Systems

within range

Range Systems

within range

Range Systems

within range

Range Systems

within range

0-30 15 0-100 14 0-50 12 < 104 0 31-100 5 101 – 250 5 51-100 9 104 – 105 4 >100 2 >250 2 >100 1 >105 9

Standard for


water

30

Standard for


water

250

Standard for


water

100

WHO guideline

for unrestricted irrigation

103

An overview of the distribution of the ASP treatment plants and of their total capacity in India is given in Figure 16.

3 WWT in Delhi were excluded as they are already covered in Kazmi (2008)


35

Figure 16: Location of the recorded Activated Sludge process plants in India (109 recorded).


36

3.13 EXTENDED AERATION (EA)


Extended Aeration systems are variant of activated sludge systems that utilizes long solids retention times (SRTs) to remove biodegradable organics. These systems are simpler in construction and operation than conventional activated sludge systems as primary settling of wastewater and anaerobic digestion of sludge are not required. Aeration is extended and sludge is mineralised enough to require only dewatering. Oxidation ditches (carousel type and pasveer type) are commonly used extended aeration systems.

A typical configuration of an extended aeration system as applied in India is shown in Figure 17.

Aeration unit Secondary clarifierSewage Pre-treatment

unit

Sludge treatment



Figure 17: Schematic layout of Extended Aeration.

3.13.2 Special features of technology The extended aeration systems are most appropriate for treatment of intermittent flows from small communities (WSP 2008). The electricity costs are higher than for conventional activated sludge due to the extended retention time.


46 documented systems are located in Himachal Pradesh, Karnataka, Orissa, Uttar Pradesh, Uttarakhand, West Bengal and Maharashtra. About 9 installations on extended aeration systems are found in Tamil Nadu executed by Water Systems India (P) Ltd, Chennai.

3.13.4 Summary of experiences with technology performance across India The performance of the systems in Shimla (Himachal Pradesh), and Jaipur (Rajasthan) was evaluated by the CPCB (2005). The systems in Shimla all fulfill the standards, whereas the treatment plant in Jaipur was not working well due to poor operation and maintenance and not working aerators. A summary of results is given in Table 7.


37

Table 7: Results of one time sampling of extended aeration systems.


effluent


effluent


effluent





range 0-30 5 0-100 5 0-50 4 < 104 0

31-100 0 101 – 250 0 51-100 1 104 – 105 0 >100 1 >250 1 >100 1 >105 5

Standard for discharge to surface water


surface water 250


100 WHO guideline for unrestricted

irrigation 103


38

3.14 TRICKLING FILTER/BIOTOWER (TF/BT)


Trickling filters (also called biofilters) are aerobic fixed film systems. Wastewater trickles through the filter media and is degraded by a biofilm growing on the filter material.

Trickling filters consist of a cylindrical tank filled with a filter bed of a highly permeable medium. The filter media should have a large surface area and large pores and is generally made of rocks, gravel or prefabricated PVC parts (Tilley et al. 2008). The filter is ventilated to assure aerobic conditions. Depending on the hydraulic and organic load, trickling filters are classified into low-rate and high-rate systems (Arceivala and Asolekar 2008).

This technology can only be used following primary clarification since high solids loading will cause clogging (Tilley et al. 2008).

A typical configuration of a trickling filter as applied in India is shown in Figure 18.

Trickling filter Secondary sedimentationSewage Pre-treatment unit (incl.

primary sedimentation)

Sludge treatment


Figure 18: Schematic layout of a Trickling filter/Biotower system.


The technology can be used on its own or in combination with activated sludge process or as a post-treatment operation for UASB effluent (WSP 2008).


Sixteen wastewater treatment plants using trickling filters are documented. They are located in Delhi, Karnataka, West Bengal, Maharashtra, Goa and Madhya Pradesh.


The Central Pollution Control Board (CPCB 2005) conducted one time testing of basic parameters (BOD, COD, TSS, faecal coliforms) of 10 trickling filters. It can be seen in Table 8 that only 50% fulfill the BOD standard for discharge to surface waters; COD and TSS concentrations are within the Indian limits.


39

Table 8: Results of one time sampling of trickling filter.







range 0-30 5 0-100 6 0-50 4 < 104 0

31-100 5 101 – 250 4 51-100 5 104 – 105 4 >100 0 >250 0 >100 1 >105 4

Standard for


water

30

Standard for


water

250

Standard for


water

100

WHO guideline

for unrestricted irrigation

103


40

3.15 CONTACT AERATION PACKAGE: SEWAGE TREATMENT SYSTEM SINTEX-NBF


It is a package aerobic wastewater treatment system consists of three tanks in series, pre-setting tank, contact aeration tank and final settling tank and are ideal for sewage treatment and reuse for medium to large residential complex and commercial complexes (Figure 19). These systems are generally prefabricated and made up of FRP.

Figure 19: Compact Aeration system

The functioning of this system is divided into three stages which plays their role in series as given below:

Solid Separation Zone

First stage transforms the influent solids to settled solids while allowing scum to float on the surface. It is a primary sedimentation zone in which settled sludge is stabilized by anaerobic digestion. The treatment efficiency of the chamber is in the range of 30 % BOD removal.

Aeration Zone

Second stage is the aerobic zone along with plastic media installed inside the tank which in turn increases the surface area and retain micro-organism long enough to digest the organic substance remained. Clear water will overflow the next treatment chamber. Air is provided through blowers and more contacting time with the slime on the plastic media, occurred, more efficient the digestion process would be. BOD removal is around 60-65%

Final Sedimentation Zone

Final stage involves the sedimentation where organic wastes are settled in the Sedimentation zone. The settled waste in the bottom of the tank is pumped back to the primary sedimentation zone as a return sludge having active biomass (MLSS) to increase the efficiency of the system and ensure the effluent quality meets the stipulated standards.


41


The compact tubular tank is easy to transport, sludge removal is once in 3 years. It works well under no load conditions to peak loading. It is a complete underground system, hence with no footprint. It can take weight up to 30 tones, hence may be installed at pathway or under car parking. Systems may be relocated or upgraded easily.


About 122 Package Contact Aeration systems were installed for various residential housing colonies, institutions, offices and hotels all over India and 79 were documented in the database.


One of system was evaluated near Ahmedabad by a third party agency in Gujarat. Reported Concentrations vary between 19 mg/l, 165 mg/l and 26 mg/l for BOD, COD and TSS, respectively.


42

3.16 ON-SITE AEROBIC PACKAGE: CONTACT AERATION SYSTEM FOR INDIVIDUAL HOUSES (STBF SERIES)

It consists of two chambers, i.e. settling and contact aeration with pall ring media. The first chamber works as a septic tank, where settleable solids are settled down and further degraded anaerobically at the bottom zone. Second stage is high specific surface area (100 m2/m3) fixed film plastic media to retain high mass of aerobic micro-organism to degrade the organic matter in the wastewater. The high specific surface area not only prevents clogging but also provides intensive contact between the wastewater and the fixed film aerobic bacteria for the fast degradation of organic matter. The treatment performance ranges at 80-95 % for BOD and SS removal.


It is easy to install and displays higher pollutant removal efficiency. The effluent may be used for gardening and other purposes.


Several plants have been implemented all over India.


Up to 90 % BOD, COD and TSS removal is claimed by the manufacturers.


43

3.17 COMPACT WASTEWATER TREATMENT PLANTS (MMBR, FAB)

Compact wastewater treatment plants (CWTP) use the same processes as conventional wastewater treatment systems. The main difference is that they are prefabricated, delivered as package and ready to use. A range of different types of CWTP is offered by private companies, under the form of Moving Bed Biofilm reactor (MBBR) or Fluidized Aerobic Bed (FAB). An overview is given in the following sections.

3.17.1 Moving Bed Biofilm Reactor (MMBR)


Fluidized Media Reactor (FMR) uses the attached growth process for waste water/sewage treatment and recycle. It incorporates a single tank unit, consisting of a bar screen chamber, specially designed floating media to facilitate the attached growth process, oxygen transfer through diffused membrane aeration, lamella settler and chlorine contact tank. The system is available in mild steel and reinforced concrete.

Figure 20: Schematic diagram of FMR.


FMR works on the same principle as the submerged fixed film process (see 3.18) with only one exception - the media is not fixed and floats around in the aeration tank. The main advantage of this system over the submerged fixed film process is that it prevents choking of the media.


Around 139 systems are used by housing complexes, hotels, commercial complexes, industries and rural communities all over India and documented in the database. Water systems pvt ltd has implemented 2 STPs with MBBR model in Ganapathy (0.1 MLD) and Tumkur (0.15 MLD) respectively.

3.17.1.4 Summary of experiences with technology performance across India There is no information available on its performance across India.


44

3.17.2 Fluidized Aerobic Bed (FAB)


FAB system is one the type of MBBR. A typical configuration of a FAB system as applied in India is shown in Figure 21.

Secondary clarifierFAB Discharge to

water bodySewage Pre-treatment unit

Sludge treatmentcirculation of effluent

Figure 21: Schematic layout of FAB type MBBR system.


The effluent of FAB may be anaerobic and require additional treatment in e.g. pond systems.


Two systems for domestic wastewater in Uttar Pradesh are documented. Besides that, about 4 FAB based STP recycle systems were installed by Thermax in Bangalore (450 KLD), Hyderabad (1000 KLD), Pune (750 and 25 KLD) for Hotels, Residential and Institutional applications. But 150 systems are documented.


The performance of the system in Lucknow, Uttar Pradesh, was evaluated (CPCB 2005). The treatment plant is not able to achieve the standards for discharge in streams as shown in Table 9. The weak performance is traced back to poor operation and maintenance. The performance of the plants in Ganapathy and Tumkur is also detailed in the Table 9. Table 9: Results of one time sampling of FAB in Lucknow.

BOD (mg/l), COD (mg/l) TSS (mg/l, Faecal coliforms (MPN/100ml)

Lucknow Raw

sewage 153 Raw sewage 297 Raw

sewage 275 Raw sewage 1.6*1011

Outlet 58 Outlet 132 Outlet 107 Outlet 1.5 x 109 Tumkur

Raw sewage 400 Raw

sewage 600 Raw sewage 500 -

Outlet <10 Outlet <100 Outlet <10 - Ganapathy

Raw sewage 350 Raw

sewage 500 Raw sewage 300 -

Outlet 15 Outlet <200 Outlet <20 - Standard

for discharge to surface

water

30

Standard for


water

250

Standard for


water

100

WHO guideline for unrestricted

irrigation

103


45

3.18 SUBMERGED AEROBIC FIXED FILM (SAFF)


The Submerged Aerated Fixed Films (SAFF) Technology uses three stages. The process uses support media to retain an active biomass to reduce the influent BOD Levels. Tubular diffusers are used with the SAFF media giving a air dispersal and low level of blockage due to growth of biological film.

SAFF reactor is a type of aerobic attached growth treatment process. Small foot print area, stable process, lesser sludge production and modular installations are the key features of SAFF process. Essentially SAFF system is a hybrid reactor where attached growth and suspended growth activity takes place simultaneously.


This technology utilizes an aerobic fixed film process that is a combination submerged attached growth and activated sludge processes.


One system is used in New Dehli.


There is no information available on its performance across India.


46

3.19 MEMBRANE BIOREACTOR (MBR)


The MBR process uses submerged membranes in the biological process water tank so as to produce high quality permeate from domestic sewage, primary and secondary waste water. MBR is also ideal for retrofitting and for augmenting capacity/quality of existing waste water treatment plants. The MBR can handle very high sludge concentrations in the aeration tank because of which the size of the aeration tank reduces four to fivefold. As the membranes act as a fine filter, no further treatment using sand filters, activated carbon filters, etc. is required (Figure 22).

Figure 22: Block diagram of MBR


It removes 6 logs of total coliforms, it is compact and requires a quarter to a third less space than a conventional system. All clarifier related problems such as sludge bulking, sludge rising, etc. are avoided as the clarifier unit itself is eliminated. It does not require costly tertiary treatment units to make the effluent suitable for recycle.


The MBR based STP recycle plants have been implemented by Thermax in Bangalore (500 KLD), Chennai (700 KLD) and Kochi (100 KLD) for Institutional and residential applications. Another MBR based STP was executed by Ecopure technologies for residential application in Tamil Nadu.


The removal rates of SS, BOD and COD are 99%, 98 and 94% respectively in the MBR plant in commonwealth Games Village, Delhi.

47

3.20 SEQUENCING BATCH REACTOR (SBR)


The Sequencing Batch Reactor (SBR) is a modification of the conventional activated sludge process. The processes involved are similar to the conventional activated sludge system, but a single reactor basin for aeration, sedimentation, clarification and surface liquid removal is used (WSP 2007). This System is operated in a batch reactor mode that eliminates all the inefficiencies of the continuous processes. The complete process takes place in a single reactor, within which all biological treatment steps take place sequentially. No additional settling unit, secondary clarifier is required. The complete biological operation is divided into cycles.

A basic cycle comprises (Figure 23):

• Fill-Aeration (F/A)

• Settlement (S)

• Decanting (D)

Figure 23: Schematic layout of SBR system

The advantages of this setup are reduced construction costs and a more stable operation also tolerating peak flows (Arceivala and Asolekar, 2008).

In this process, four different phases are carried out - filling while aeration is in process, settling of the aerated sewage, settled sludge is decanted while the treated water overflows for further chlorination (WSP, 2007).

48

A typical configuration of a SBR system as applied in India is shown in Figure 24.

SBR reactor Discharge to water bodySewage Bar

screen

Sludge treatment

Equalization tank

Figure 24: Schematic layout of SBR system.


The technology can treat all different types of wastewater on limited space.


Around 170 installed SBR systems are reported all over India (Figure 25).


As per the evaluation of SBR all over India by IIT Roorkee, it was found out that most of these plants are discharging BOD < 10 mg/L, COD < 50 mg/L, TSS 10-20 mg/L.The performance of the SBR system (0.5 MLD) executed in an engineering college Coimbatore, Tamil Nadu exhibits removal rates of BOD, COD and TSS to 95.7%, 60% and 95% respectively.

49

Figure 25: SBR treatment plants location in India (171 plants) in function of their total capacity.

50

4 Description of technologies for black water treatment

4.1 ANAEROBIC BAFFLED REACTOR


See description of technology in section 3.5.123




This system is used for treating wastewater from toilet complexes (in some cases with laundry and/or shower) in Karnataka and Kerala.


CDD India4 provides information about the performance of selected ABR systems for black water treatment. Only 50% of the systems fulfill the standard for BOD; COD concentrations are within the limit. Table 10 gives a summary of the results.

Table 10: Results of one time sampling of Anaerobic baffled reactor.





Range within range

Range within range

Range within range

Range within range

0-30 3 0-100 4 0-50 2 < 104 4 31-100 3 101 – 250 2 51-100 3 104 – 105 1 >100 0 >250 0 >100 1 >105 0 Standard for discharge to surface water




no std

4www.cddindia.org

51

4.2 ANAEROBIC FILTER (AF)




See description of technology in section 3.8.2.


There is one example of an anaerobic filter for black water treatment in Delhi.


CDD India5 provides information about the performance of the anaerobic filter for black water treatment. Table 11 shows the results. All parameters are within the limit.

Table 11: Results of one time sampling of the anaerobic filter in Delhi.

BOD (mg/l), COD (mg/l) TSS (mg/l)

Raw sewage 30 Raw sewage 37 Raw sewage 30

Outlet 20 Outlet 72 Outlet 7




100

5www.cddindia.org

52

4.3 BIOGAS DIGESTER WITH OPTIONAL EFFLUENT TREATMENT

An anaerobic biogas reactor is a chamber in which anaerobic degradation of blackwater, sludge, and/or biodegradable waste takes place. Prefabricated tanks or brick-constructed chambers can be built depending on local conditions. Biogas reactors can be built as fixed dome or floating dome reactors (Tilley et al., 2008). Biogas can be used as an alternative source of energyfor use in household cooking, heating, lighting and for municipal and industrial use (WSP 2007).

Optional, an additional treatment unit (e.g. constructed wetlands, aeration units or sand filters) can be installed to improve the effluent quality (see Pathak 2011 for an example).

A typical configuration of a biogas reactor as applied in India is shown in Figure 26.

Toilets Biogas digester

Sludge treatment

(CW or sand filters)

Discharge to water body or irrigation/gardening

Biogas

Figure 26: Schematic layout of biogas digester system

Biogas reactors are best used for wastewater with high organic pollution. Anaerobic biogas settlers are often used as a primary settling treatment in decentralised wastewater treatment systems.

4.4 CONSTRUCTED WETLAND

See description of technology in section 3.5.2.

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5 Description of technologies for grey water treatment

5.1 MULTIPLE STEP FILTRATION


Greywater is applied to the top of first filter, percolates through an unsaturated zone of porous material and is then collected in a drainage system (Morel and Diener 2006). Suspended solids are removed by filtration and organic matter is degraded by microorganisms colonising the filter material. The first filter is the coarsest material (e.g. gravel) and the last step (of usually five or more) is fine sand or charcoal.

A typical configuration of multiple step filtration system as applied in India is shown in Figure 27.

Multiple step filtration unit

(Constructed wetland)

Grey water

Equalization tank Chlorination Toilet flushing

Figure 27: Schematic layout of multiple step filtration system.


Optionally, a constructed wetland can be used as additional treatment step. After chlorination, the treated grey water can be used for various purposes. In the Indian case studies, effluent was reused for toilet flushing.


Multiple step filtration systems for grey water treatment have been implemented in six schools in Madhya Pradesh.


Only for thermoTolerant coliforms (TTC) performance results are available. Figure 28 shows that almost all systems comply with the Australian guideline value of 10.000 cfu/100ml.

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Figure 28: Evaluation results (Source: Mooijman (2007) UNICEF).

55

5.2 PLANTED FILTER

5.3 BRIEF DESCRIPTION OF TECHNOLOGY

Planted filters for grey water treatment (also called sub-surface flow vertical flow constructed wetlands, see section 1.1.1) are similar to conventional filters with the difference that roots of plants (often canna indica) increase the hydraulic conductivity of the bed. Grey water passes the filter bed where filtration and aerobic degradation take place and is then collected by a drainage network at the base (Morel and Diener 2006).

A typical configuration of planted filter system as applied in India is shown in Figure 29.

Planted filterGrey water Gardening

Figure 29: Schematic layout of planted filter system


No special features


Only two systems in Tamil Nadu and Gujarat are documented.


Performance results are not documented.

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5.4 WASTE STABILISATION PONDS (WSP INCLUDING FLOATING WETLANDS)

5.4.1 Floating aquatic plant systems (duckweed, water hyacinth)


Aquating plants that are floating on the water surface are improving removal of pollutants of conventional pond system. They cover the surface of the water and prohibit algae growth. The main plants used in floating aquatic plant systems are duckweed (Lemnaceae) and water hyacinths (Eichhornia). The systems are designed like conventional waste stabilization ponds, but in addition measures to reduce the influence of wind which can blow the duckweed away, are taken. In India usually floating bamboo grits are used to control the impact of the wind.

A mat of duckweed or water hyacinths covers the surface of the ponds creating anoxic-anaerobic conditions which favour denitrification (Arceivala and Asolekar 2007). Mosquito breeding and odour are reduced.

A typical configuration of a duckweed pond as applied in India is shown in Figure 30.

Fish pondDuckweed pond Irrigation Sewage Settling unit

Figure 30: Schematic layout of duckweed pond system


The biomass generated during the treatment can be fed to fish or other animals. Therefore, duckweed ponds are often combined with fish ponds. The most often reared fish species fed with duckweed in India are Catla, Rohu, Grass Carp, Common carp, Silver carp and Mrigal.

Duckweed ponds can also be used as tertiary treatment in conventional pond systems.


Duckweed ponds have been implemented in Punjab (Figure 31), Pondicherry and Delhi. The Government of Punjab has launched a plan to revive dirty village ponds for fish farming by adopting duckweed technology. Around 20 systems have been implemented in rural Punjab so far (Figure 31).

Duckweed ponds are used as tertiary treatment in a pond system in Pondicherry. One demonstration plant implemented by Sulabh International is located in Delhi.

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Figure 31: Location of duckweed ponds in Punjab.

5.4.1.3.1 Summary of experiences with technology performance across India

For the systems in Punjab no results of the technical performance are available.

Duckweed ponds are used as additional treatment step in a pond system in Pondicherry. BOD reduction of the complete treatment process was recorded as 77%. Total suspended solids were reduced by 99% and the effluent contained 1280 MPN E.coli per 100 ml. Duckweed is not used for any purpose (Fardin et al. 2011).

Total hydraulic retention time in the system in Delhi in the series ofthe four ponds is 27-28 days. BOD of the effluent after the third pond is around 30 - 40 mg/l. The growth rate of duckweed is about 130 g/m² per day. This case study showed that the presence of grease concentrations above 10 mg/l and the presence of cyanobacteria can impede duckweed growth (Iqbal 1999).

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5.4.2 Floating wetland (WSP)

5.4.2.1 Brief description of technology Floating wetlands are a variation of conventional constructed wetlands (Figure 32) and do not figure in

Table 1. Rooted, emergent plants (similar to those used in surface and subsurface flow applications) are growing as a floating mat on the surface of the water. Plants may either be arranged on a floating raft structure and rooted in soil media (Headley et al. 2006).

Figure 32: Schematic layout of floating wetland system (Source: Headley and Tanner, 2006).


Artificially created floating wetlands have been used for treatment of stormwater, combined stormwater-sewer overflow, sewage, industrial wastewater (mainly food processing) and drinking water reservoirs (Headley and Tanner, 2006).


One demonstration system has been installed at River Kshipra in Madhya Pradesh.


No data has been published on the treatment performance of this system.

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5.5 EXTENDED AERATION (EA)


The wastewater is treated in an aerobic suspended growth system (extended aeration, see section 3.13.1). The tertiary treatment comprises of a bio gravity vermi filter with root zone plants and disinfection to make the safe reuse possible (UN-Habitat 2009).

The configuration of the extended aeration system as applied in India is shown in Figure 33.

Aeration unit Settling tankGrey water

Bar screen and collection tank Chlorination Planted soil

vermi-filter

Sludge treatment


Toilet flushing/gardening

Figure 33: Schematic layout of the extended aeration system


No special features.


This system was implemented at a campus in Indore, Madhya Pradesh. 9 other instances of implementation of extended aeration biological system have been executed in Tamilnadu and Karnataka.


The performance was tested in September three consecutive years (UN-Habitat 2009). The result are summarized in Table 12. All tested parameters are within the Indian standard for discharge to surface waters.

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Table 12: Results of sampling of extended aeration system in Madhya Pradesh, Tamilnadu and Karnataka.

BOD (mg/l), COD (mg/l) TSS (mg/l) Oil and grease (mg/l)

Madhya Pradesh Sept. 2007 8 Sept. 2007 39 Sept. 2007 38 Sept. 2007 3.4 Sept. 2008 15 Sept. 2008 105 Sept. 2008 41 Sept. 2008 4.1 Sept. 2009 22 Sept. 2009 130 Sept. 2009 36 Sept. 2009 4.6

Tamilnadu 15 <200 <20 <10 15 <200 <20 <10

< 20 < 250 < 30 < 10 20 < 250 < 30 < 10 15 < 200 < 20 < 10

Karnataka < 10 < 100 < 10 < 10 10 < 150 < 10 < 10 15 < 200 < 20 10 15 < 200 < 20 < 10





10

Standard for irrigation 100 Standard for

irrigation - Standard for irrigation 200 Standard for

irrigation 10

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5.6 GRAVEL FILTER


This technology consists of a pre-treatment unit followed by an up-and downflowgravel filter as secondary treatment. The effluent passes a step aeration unit and is stored in a tank to be reused for irrigation and toilet flushing (Mandal et al., 2011).

The configuration of the gravel filter system as applied in India is shown in Figure 34.

Gravel filter unit

Step aeration

Grey water

Storage tank

Toilet flushing /irrigation

Screen and coarse filter

Collection tank

Figure 34: Schematic layout of the gravel filter system


This system was implemented for a single household, but has potential to be implemented at larger scale (Mandal et al., 2011)


This grey water treatment unit is installedin Nagpur, Maharashtra.


The performance of the system was tested in consecutive months. The results are summarised in Table 13 and show that the water complied with the Indian standard for discharge to surface waters and for irrigation. More parameters, bio-chemical and microbiological, can be found in Mandal et al. (2011). Table 13: Results of sampling of extended aeration system in Indore.

BOD (mg/l), COD (mg/l) TSS (mg/l) FC (cfu/100ml)

May 2010 40 May 2010 140 May 2010 9 May 2010 2x104

June 2010 ND* June 2010 56 June 2010 12 June 2010 nil





no standard

Standard for irrigation

100 Standard for irrigation

- Standard for irrigation

200

ND = not detectable

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6 Discussion and conclusion

The documentation has shown that various types of wastewater treatment technologies have already been implemented at different sizes across India. The majority of these technologies have been implemented by private real estate developers, housing societies, colonies, institutional and commercial areas and non-polluting industries which do not discharge process wastewater for the separate treatment of sewage. In addition, there are several treatment plants implemented by municipalities.

As shown in chapter 2, the studied technologies correspond to four main groups of areas: (1) Rural Areas with cheaper land availability and package on-site septic systems for all areas; (2) Rural Areas and peri-urban areas with cheaper limited space; (3) Peri-Urban areas with expensive and limited space; (4) Peri-Urban areas with expensive and limited space and strict effluent quality. The decentralized sewage treatment plants are mainly found in rural areas with cheaper land availability (39 %) (Table 14).

Table 14 : Number of sewage treatment plants per type of context.

Context Number of STP % Peri-Urban areas with expensive and limited

space 308 20

Peri-Urban areas with expensive and limited space and strict effluent quality 324 21

Rural Areas and peri-urban areas with cheaper limited space 244 16

Rural Areas with cheaper land availability and package on-site septic systems for all areas 585 39

unknown 56 4

Total 1517 100

The total capacity of the documented sewage treatment plants varies greatly between 0.0002 to 635 mld.

The survey has shown that there is very limited or no evaluation of the performance, in particular of smaller scale plants, available. Saraswati will continue with an integrated evaluation of selected smaller scale wastewater treatment plants to provide some scientific evidence of the actual performance of these plants in India.

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7 References

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Baetens T., Boulicot G., Kostedde L. (2009). Natural Decentralised Wastewater Treatment Systems, Auroville Centre for Scientific Research (CSR), Tamil Nadu, India

Beychok, M. R., 1967. Aqueous Wastes from Petroleum and Petrochemical Plants (1st ed.). John Wiley & Sons, 262 pages

Bhuptawat, H., Folkard, G.K., Chaudhari, S. (2007). Innovative physico-chemical treatment of wastewater incorporating Moringa oleifera seed coagulant. Journal of Hazardous Materials 142, 477-482.

CPCB (2005). Status of water supply, wastewater generation and treatment in Class-I cities & Class-II towns of India, in: 10, C.o.u.p.S.C.-. (Ed.).

Fardin, F., Holle, A., Gautier, E. and Haury, J. (2011). Spatial, Technological and Social Aspects of Wastewater Treatment in Puducherry Region, Presentation

Foxon, K.M.,Pillay, S.,Lalbahadur, T.; Rodda, N., Holder, F.,Buckley, C.A. (2004). The anaerobic baffled reactor (ABR)- An appropriate technology for on-site sanitation.. In: Water SA 30, 5

Headley, T.R., Tanner, C.C. (2006). Application of Floating Wetlands for Enhanced Stormwater Treatment: A Review. Auckland Regional Council.

Iqbal, S. (1999), Duckweed Aquiculture, Potentials, Possibilities and Limitations for Combined Wastewater Treatment and Animal Feed Production in Developing Countries, SANDEC Report No. 6/99

Kazmi, A.A., Tyagi, V.K., Trivedi, R.C.,Kumar, A. (2008). Coliforms removal in full-scale activated sludge plants in India, Journal of Environmental Management 87 (2008) 415–419

Mandal, D., Labhasetwar, P., Dhone, S., Dubey, A.S., Shinde, G., Wate, S. (2011). Water conservation due to greywater treatment and reuse in urban setting with specific context to developing countries. Resources, Conservation and Recycling 55, 356-361.

Mooijman, A., 2007. Water, Sanitation and Hygiene (WASH) in Schools, in: UNICEF (Ed.)

Morel A., Diener S. (2006). Greywater Management in Low and Middle-Income Countries, Review of different treatment systems for households or neighbourhoods.Swiss Federal Institute of Aquatic Science and Technology (Eawag).Dübendorf, Switzerland.

Pathak B (2011). Sulabh sanitation and social reform movement, International NGO Journal, Vol. 6(1), pp. 014-029.

Starkl, M., Kazmi, A.A., Cary, L., Essl, L., Singh, A., Nimkar, I., 2013. Up-scaling of Decentralised Wastewater Management Solutions: Lessons Learned and Way Forward in India, IWA ASPIRE, Daejeon, Korea.

Tchobanoglous, G.(1991). Wastewater Engineering – Treatment, Disposal, Reuse, Metcalf & Eddy Inc., Third Edition, McGraw-Hill Book Co, Singapore

Tare, V., Nema, A. (n.y.) UASB Technology-expectations and reality. United Nations Asian and Pacific Centre for Agricultural Engineering and Machinery.

Tilley, E., Lüthi, C., Morel A., Zurbrügg C. and Schertenleib R. (2008)Compendium of Sanitation Systems and Technologies, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf, Switzerland

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Ulrich,A., Reuter, S., Gutterrer, B.(editors) with Sasse, L., Panzerbieter, T. and Reckerzügler, T. (2009), Decentralised Wastewater Treatment Systems (DEWATS) and Sanitation in Developing Countries – A Practical Guide, WEDC, LoughboroughUniversity,UKin association with BORDA, Germany

Vipat, V., Singh, U.R., Billore, S.K. (2008) Efficacy of Rootzone Technology for Treatment of Domestic Wastewater: Field Scale Study of a Pilot Project in Bhopal. (MP), India, Proceedings of the Taal2007: the 12th World Lake Conference: 995-1003

World Bank (2008) Technology Options for Urban Sanitation in India. A Guide to Decision-Making, Water and Sanitation Program

WEF (2010), Biofilm reactors, Alexandria, USA

WSP (2007) Philippines Sanitation Sourcebook and Decision Aid, Water and Sanitation Program, Washington, USA

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