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KHANH HOA PROVINCIAL PEOPLE'S COMMITTEE

NHA TRANG CITY ENVIRONMENTAL SANITATION PROJECT MANAGEMENT UNIT

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REPORT

ENVIRONMENTAL IMPACT ASSESSMENT

COASTAL CITIES ENVIRONMENTAL SANITATION PROJECT

NHA TRANG SUB-PROJECTS

COMPONENT 2· WASTEWATER TREATMENT PLANT (FINAL DRAFn

NHA TRANG, JANUARY 2011

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wb370910Typewritten TextE1295 v. 12

KHANH HOA PROVINCIAL PEOPLES COMMITTEE NHA TRANG CITY ENVIRONMENTAL SANITATION PROJECT MANAGEMENT UNIT

REPORT

ENVIRONMENTAL IMPACT ASSESSMENT

COASTAL CITIES ENVIRONMENTAL SANITATION PROJECT

NHA TRANG SUB-PROJECTS

COMPONENT 2· WASTEWATER TREATMENT PLANT (FINAL DRAFT)

INVESTOR CONSULTANT

NHA TRANG aTV ENVIRONMENTAL LAC VIET INVESTMENT, ENVIRONMENTAL

SANITAnON PROJECT MANAGEMENT UNIT TECHNOLOGY AND INFRASTRUCTURE TECHNIQUES JSC., (LAVIC)

Coastal Cities Environmental Sanitation Project (CCESP) - Phase 2

Nha Trang City SulJ...prqiect Component 2 - Wastewater Treatment Plant

LIST OF FIGURES

Page

Figure 1-1: Satellite map of the North WWTP ..................................................................................................... 7

Figure 1-2: Map a/proJect location in Nha Trang City ....................................................................................... 8

Figure 1-3: Satellite map ofSouthern WWTP ...................................................................................................... 9

Figure 14: The flowchart 0/wastewater treatment technology .................................................................... 10

Figure 1-5: General designing 0/wastewater treatment technology ............................................................. 10

Figure 1-6: Block diagram ofsludge treatment solution ................................................................................. 14

Figure 2-1: Diagram ofenllironmental quality sampling locations ................................................................. 28

Figure 4-1: Calculated concentration of BOD - Cai river................................................................................... 51

Figure 4-2: Calculated concentration ofCOD - Cai river ............................•...................................................... 51

Figure 4-3: Calculated concentration ofAmon; - Cai river ................................................................................ 52

Figure 4-4: Calculated concentration of Total N - Cai river .............................................................................. 52

Figure 4-5: Calculated concentration of Total P - Cai river .........................................................•....•................ 53

Figure 4-6: Calculated concentration of BOD of Tac - Quan Truong river ....................................................... 55

Figure 4-7: Calculated concentration ofCOD of Toe - Quan Truong river ....................................................... 55

Figure 4-8: Calculated concentration 0/Amoni ofTac - Quan Truong river ..................................................... 56

Figure 4-9: Calculated concentration of Total-N ofTac - Quan Truong river ................................................... 56

Figure 4-10: Calculated concentration ofTotal-P ofTac - Quan Truong river ................................................. 57

Figure 6-1: Map ofenvironmental monitoring locations in the construction phase for Component 2.............. 75

Figure 6-2: Map ofenvironmental monitoring locations in the operation phase for Component 2.................. 76

Figure 6-3: Flowchart 0/EMP implementation reporting .................................................................................. 77

Report (IfEIA, Lavic Ctmsultalft, Jalfuary, 2011 iii


Nha Trang City SuiJ..prqject Component 2 - Wastewater Treatment Plant

LIST OF TABLES

Page

Table 1-1: Capacity of Wastewater Treatment Plant - Component 2 ............................................................... 10

Table 1-2: Components and equipments used for wastewater treatment piant............................................... ll

Table 4-10: The total amount ofemission from fuel burning for operating machines/vehicles at site

Table 1-3: The Schedule ofProject Implementation Plant ................................................................................. 16

Table 1-4: Summary ofproject cost ................................................................................................................... 17

Table 1-5: Investment plan for component 2 Phase 2 WWTP North and South .............................................. 17

Table 2-1: Wind speed in dominant directions (m/s) ......................................................................................... 21

Table 2-2: Average monthly and annual air humidity at Nha Trang station (%) ............................................... 21

Table 2-3: Total ofmonthly and annual evaporation capacity (mm) ................................................................ 21

Table 2-4: Average monthly and annual sunshine hour variation in Nha Trang station (%) ............................. 22

Table 2-5: Some features of typhoons in Khanh Hoa ......................................................................................... 22

Table 2-6: Production value at current price of Nha Trang City divided by economic sectors in 2005 - 2007 .. 23

Table 2-7: Production value ofagriculture at current price ofNha Trang City .................................................. 23

Table 2-8: Average population ofNha Trang City 2004 - 2008......................................................................... 24

Table 2-9: Rate of toilet rypes ofhouseholds in Nha Trang City ........................................................................ 25

Table 2-10: Current situation of types of toilets ofhouseholds in Nha Trang City ............................................. 25

Table 2-11: Analysis results ofambient air quality ............................................................................................ 27

Table 2-12: Analysis results ofsUrface water quality in the study area ............................................................. 29

Table 2-13: The analysis results ofgroundwater quality at project area ........................................................... 30

Table 4-1: Sources, objects and degree of impacts of the project .................................................................... 37

Table 4-2: Land acquisition area on the construction site for WWTPs in Component 2 .................................... 40

Table 4-3: Impacts in the period of the site clearance ...................................................................................... 41

Table 4-4: Estimation ofdiesel oil consumption ............................................................................................... 42

Table 4-5: Predicted concentration ofair pollutants ........................................................................................ 42

Table 4-6: Emission factor ofdust pol/ution in construction activities ............................................................... 43

Table 4-7: Estimation ofdust emIssion in construction activities ..................................................................... 43

Table 4-8: Emission factors ofsome vehicles on site ......................................................................................... 43

Table 4-9: The total amount ofdiesel used for main construction vehicles on site ........................................... 44

construction.................................................................................................................................... 44

Table 4-11: Maximum noise level according the distance ofconstruction equipment ...................................... 45

Table 4-12: Load ofpollutants in domestic waste water .................................................................................. 46

Table 4-13: Environmental Impacts in the construction phase ......................................................................... 48

Table 4-14: The predicted changes in pollutant Concentration along Cai River ............................................... 50

Table 4-15: Summary of the Calculation Result of Cross Sections along Tac - Quan Truong River ................... 54

Table 4-16: Environmental impacts during the operation period . ..................................................................... 59

Table 6-1: Summarized plan for mitigation measures ....................................................................................... 67

Table 6-2: Environmental Monitoring Programe ofComponent 2 .................................................................... 72

Table 6-3: Locations ofmonitoring sites ofenvironmental monitoring programme ......................................... 73

Table 6-4: Institutional Responsibilities ............................................................................................................. 78

Table 6-5: Environmental Training Program for Constructor...................... ....................................................... 79

Table 6-6: Costfor Environmental Monitoring Program for each WWTP .......................................................... 80

Table 6-7: Cost estimation for implementation ofcapacity building and training ............................................ 81

Table 6-8: Total cost for environmental management plan .............................................................................. 82

Table 7-1: First round public consultation conducted by LAVlC......................................................................... 84

Table 7-2: Second round public consultation conducted by LAVIC..................................................................... 85

ABBREVIATION

Repflrt 0/ErA, Lavic CI'1I.'.ultanl, Janllilry, 2011 iv


Nha Trang City Sub-project Component 2 - Wastewater Treatment Plant

ADB CAS DOC DOF DPI DONRE EAI EMP EIRR FIRR FS GSO GoV MOF LAVIC

MOC MPI MOSTE NRW NPV O&M PPC PMU PC PM URENCO USD VND VAT WB WSDC WWTP

Asian Development Bank Country Assistance Stratergy Department of Construction Department of Finance Department ofPlanning and Investment Department ofNatural Resources and Environment Environment Impact Assessment environment management plan Economic internal rate of return Financial Internal Rate of Return Feasibility Study General Statistics Office Government of Vietnam Ministry ofFinance Lac Viet Investment, Environmental Technology and Technical Infrastructure Joint-Stock Company Ministry ofConstruction Ministry ofPlanning and Investment Ministry of Science Technology and Environment Non Revenue Water Net Present Value Operation and Maintenance Provincial People's Committee (Vietnam) Project Management Unit People's Committee Prime Minister (Vietnam) Urban Service and Environment Company United Sates Dollar Vietnam Dong Value Added Tax WorIdBank Water Supply and Drainage Company Wastewater Treatment Plant

Rf!JHIrl tlfEIA, Lavk ClIn"'ultant, January, 1011 v

Coastal Cities Environmental Sanitation Project (CCESP) - Phase 2 Nha Trang City Sub-project Component 2 - Wastewater Treatment Piant

INTRODUCTION

1. PROJECT BACKGROUND

Nha Trang Environmental Sanitation Project is one of three sub-projects under the coastal cities environmental sanitation project. The Project is proposed to solve the existing serious environmental sanitation problems. to improve environmental sanitation conditions of the cities and the people's living conditions as well as to ensure sustainable economic development

The Project is financed by the World Bank and includes 6 components:

Component 1: Drainage. flood control and wastewater collection

Component 2: WWTP

Component 3: Solid waste management

Component 4: Development of resettlement area

Component 5: Revolving Fund and school sanitation Program

Component 6: Capacity building and implementation support

The Project is divided into two phases: (i) first phase: from 2006 to 2011; and (ii) second

phase: from 20 II to 2014.

Currently, the packages of the first phase are in the completion process and the Project

Management Unit is preparing for the phase 2. The components in phase 2 include:

Component 1: Drainage/ flood control and wastewater collection in the north, the centra]

and the south of the city

Component 2: Build two WWTPs in the north and the south of the city

Component 3: Solid waste management

(i) Expand sanitary landfill and other components at the Luong Hoa landfill that was built in the first phase.

(ii) Build the waste transfer stations in different locations in the city

(iii) Provide additional equipments for solid waste collection

Component 5: Revolving Fund and school sanitation Progranl

Newly build and rehabilitate the toilets of 10 schools including kindergartens, primary schools, secondary schools and high schools in the inner city ofNba Trang.

In phase 2, only component 2 is newly invested. The components 1, 3 and 4 have been implemented partly in phase 1 ofproject.

In order to complete necessary legal procedures, the Project Owner has collabomted with the consulting unit - Lac Viet Investment, Environmental Technology and Infrastructure Engineering JSC (LA VIC) - to prepare the environmental impact assessment report and the environment management plan in accordance with the regulation on environment protection ofthe Vietnamese Government and the World Bank.

Repm1 ofEIA, Lavic Consultant, JanUllIY, 2011


Nha Trang City Sub-prC?iect Component 2 Wastewater Treatment Plant

In the framework of this report, the Consultant LACVIC shall evaluate the impacts on envirOlIDlent, social and environment management plan for the implementation of Component 2: Build wastewater treatment systems in the north and south of the city. 'Ibe impacts incJude potential, positive and negative, direct and indirect, long tenn and short tenn. Based on these forecast and assessment, mitigation measures (include management and technical measures) shall be proposed to take full advantage of the positive impacts and minimize the negative impacts on natural and social environment during the project implementation.

2. LEGAL DOCUMENTS

2.1. Legal basis

- Law on Environmental Protection No. 5212005/QH II dated November 29, 2005 of the National Assembly, the Socialist Republic of Vietnam;

- Decree No. SO 120061ND- CP dated August 09, 2006 of the Government, detailing and guiding the implementation of a number of articles of the Law on Environmental protection;

- Decree No. 211200SIND-CP dated February 2S, 200S, amending and supplementing a number of articles of the Government's Decree No. 80 120061ND- CP dated August 09, 2006 of the Government detailing and guiding the implementation of a number articles of the Law on Environmental protection;

- Circular No. 05/200Sffi· BTNMT dated December S, 200S of the Ministry of Natural Resource and Environment, guiding strategic environmental assessment, environmental impact assessment and environmental protection commitment~

- Directive No. 4S7ffig dated June 30, 1996 of the Prime Minister: Enhance State management of water resources;

- Decree No. 209/20041ND-CP dated of December 16, 2004 of the Government on the quality management ofconstruction works;

- Decree No. 16/20051ND·CP dated February 07, 2005 of the Government on the management of construction investment projects;

- Decree No. 112/20061ND-CP dated September 29, 2006 of the Government about the adjustment and supplement of some components in Decree No. 16/20051ND-CP on the management ofconstruction investment pr~iects;

- Decree No. 88/20071ND-CP dated May 28, 2007 on Urban and Industrial Zone drainage;

- Decision No. 13/2007/QD-BXD dated December IS, 2006 of the Ministry of Natural Recourse and Environment about the compulsory compliance of Vietnamese slandards on Environment;

- Decree No. 04/20071ND-CP of the Government: adjustment and supplementation of some articles in the Government's Decree No. 67/2003/CP dated June 03, 2006 on environmental protection charges applicable to wastewater;

- Office Letter No. 175112007IBXD • VP dated August 14, 2007 of the Ministry of Construction on the issuance of Nonn of project management costs and project investment construction and consultant costs; and

Rl!ptlrl tifEM, Lavic Co"sulta"t, Ja"uary, 2011 2



- Law on Construction No. 16/2003/QH11 dated November 26. 2003 of the National Assembly, the Socialist Republic of Vietnam.

2.2. Related documents

• Decision No. 65/TTg-CN dated January II, 2006 which approved the Report on Feasibility studies of the Project for environmental sanitary of coastal cities - the subproject for Nha Trang City;

• The Memorandum of the Project for environmental sanitary of coastal cities, preparation delegation for sub-project ofNha Trang City~

• The Package Design and Consultant Contract for phase 1 which was signed by and between the Project Preparation Board and Vietnam Water and Environment Company on Junc 17,2005;

• The Memorandum of working content at Nha Trang between Work Bank Missions and the People's Committee ofKhanh Hoa province on March 5, 2004;

• The Tenns of Reference (TOR) of the World Bank Mission and the Project Preparation Board on March 25, 2004~

• The general adjustment plan of Nha Trang until 2020 and the general plan of Con Minh area until 2020 (now under construction);

• Report on Project concept of the international coordinator, the reports of international experts on waste water treatment and solid waste~ experts on resettlemen~ the frame policy on resettlement supporting for the project;

• Report on Feasibility Studies made by the Vietnam water and environment company in September 2005 and approved by the World Bank and Khanh Hoa province; and

• The Report on phase 1 concept made by the Vietnam water and environment company in September 2005 and approved by the World Bank and Khanh Hoa province.

The standards and regulations applied for the environmental sanitation subproject of Nha Trang City are listed as bellows:

Standard Content 22TCN 224-93 Road motor vehicles: - Technical safety and environmental

protection inspection process TCVN 5298-1995 General requirements of wastewater and its sediment for

irrigation and fertilization TCVN 5302-1995 General requirements for land reclamation (mining activities

and the landfill) TCVN 5524-1995 General requirements about protection ofsurface water from

being polluted TCVN 5525-1995 General requirement about underground water protection QCVN 03:20081BTNMT National technical regulation on the allowable limits of

heavy metals in the soils QCVN 05: 2009IBTNMT National technical regulation on ambient air quality QCVN 06: 2009IBTNMT National technical regulation on hazardous substances in

ambient air QCVN 07:20081BTNMT National technical regulation on hazardous waste; QCVN 08:20081BTNMT National technical regulation on surface water; QCVN 09:20081BTNMT National technical regulation on undergrmmd water;

Rep(}rl (ifEM, Lavic Consultant, January, 20] J 3


Nha Trang City Sub-prq;ect Component 2 - Wastewater Treatment Plant

Standard

QCVN 10:200S/BTNMT

QCVN II :20081BTNMT

QCVN 14:2008/BTNMT

QCVN 25:20081BTNMT

TCVN 5948-1995 TCVN 5949-1995

TCVN6962:2001:

TCVN 5970-1995 TCVN 5980-1995 TCVN 5999-1995 TCVN 6431-1998

TCVN 6436-1998 TCVN 6438-2001

TCXD 66-1991 TCVN 6772:2000

TCVN 6774:2000 TCVN 6696- 2000

TCVN6705 TCVN6706 TCVN7222: 2002

QCVN 01120091BYT QCXDOI/2008IBXD TCVN 7957: 2008

Content National teclmical regulation on coastal water quality; National technical regulation on industrial waste water of aquatic product treatment; National technical regulation on domestic wastewater;

National technical regulation on wastewater of solid waste landfills; Maximum permitted noise level by means ofroad transport Maximum permitted noise level in the public places and residential areas Vibration and shaking: Vibration caused by construction and industrial production activities - maximum permitted level for environment in public places and residential areas. Make plant for surrounding air quality monitoring. Water quality - Quality standard for underground water. Instruction to take wastewater sample (ISO 5667-10:1992) Means of road transportation - Exhausted fumes that caused pollution that emitted from cars and motors \\ith gasoline engme Noise emitted from means of road transport when parking Air quality - Exhausted fumes from means of road transport maximwn permitted limitation Operation ofwater drainage system - Safety regulation Water quality - Life wastewater - Maximum permitted pollution limitation Water quality - Quality of freshwater for aquatic life protection

Solid waste - hygienic landfills, general requirements about environmental protection. Classification ofnon-hazardous waste -Classification ofhazardous waste General environmental requirements for life wastewater concentration treatment plant. National technical regulation on drinking water Vietnam construction regulation - Construction plan Drainage, network and external works - Design standard.

2.3. Environmental policies of the World Bank

Besides the environmental review and approval procedures of the Vietnamese Government applied to coastal cities environmental project. Nha Trang City sub-project must be prepared and implemented in compliance with environmental and social safety policies of the World Bank. According to these safety policies, the World Bank has classified the project as type A project that has negative impacts on the environment, at a large scale and has multi dimensional and unprecedented impacts. These effects can cover a large area than the construction area.

According to the requirements of World Bank, the environmental assessment (EA) of projects has to prepare and propose a financing bank to ensure that they are environmentally sound and sustainable, and thus to improve decision making. The polices, requirements and regulations ofWB are applied for EIA and RAP including:

• Environment assessment - Operation Process / Procedures of the Bank (OPIBP 4.01):

ReptJrl ofEIA, Lavic Ctmsultant, January, 2011 4



• Physical Cultural Resource (OPIBP 4.11) • Involuntary Resettlement (OPIBP 4.12)

Consultation: According to the operation procedures of the World Bank and the Decree No. 211200SIND-CP, an A-type project must be consulted two times, the content of each consultation program must be recorded.

The first consultation win be conducted for households who can be affected by the project component implementation. This consultation process shall be conducted with the Program of economic-social survey and the environmental data collection from the project implementation area. The second consultation about the Draft Report on Environmental impact assessment for component 2 was conducted in May 2010. Meeting minutes of the consultation meetings are attached in the annex.

Disclosure of information: According to the operation procedures of the World Bank and the Decree No. SO/2006!ND-CP and the Decree No. 211200S!ND-CP, Report on Environmental impact assessment must be mass published. The Report on Environmental impact assessment must be displayed at Washington DC, Vietnam Development Information Center (VDIC) in Hanoi, People's Committee of Nha Trang City, Khanh Hoa Department ofNatural Resources and Environment. Project Management Unit of the Project for improvement of environmental sanitation of Nha Trang City, People's Committee of communes in the research area ofthe project.

Technical documents:

The Report on feasibility studies of the Project for environmental sanitary ofcoastal cities the sub-project for Nha Trang City made by Vietnam Water, Sanitation and Environment Joint Stock Company (VIW ASE).

• Primary dcsign for thc Componcnt of drainagc, phase 1 - thc Project for environmental sanitary of coastal cities - the sub-project for Nha Trang City made by VIW ASE in November 2005;

• Report on investment for the construction of solid waste landfills made by Louis Berger and Nippon Koei Joint Venture in December 2005;

• Feasibility studies Report on Component 2 Wastewater Treatment Plant, Fichtner, May 2010.

3. IMPLEMENTATION ORGANIZATION

3.1. The Consultant

Lac Viet Investment, Environmental Technology and Infrastructure Techniques Joint Stock Company (LA VIC)

Representative: Mr. Nguyen Phan Anh Position: Director Address: No.9, Duong Thanh Street, Hoan Kiem District, Hanoi. Tel: (04) 39232977

Email: [email protected]

3.2. Implementation procedures

The Environmental Impact Assessment Report (EIA) on the component 2 of "Environmentol sanitfJtion Project - NIta Trang City" was produced by Lac Viet Investment, Environmental

Report ofEM, Lavic emf,vllitant, Janllary, 2011 5

mailto:[email protected]


Nha Trang City Sub-prQiect Component 2 - Wastewater Treatment Plant

Technology and Infrastructure Techniques Joint Stock Company (LA VIC). The report was also prepared with the cooperation of laboratory staffs from Microclimate Center, Institute of Tropical Architecture, IJanoi University ofArchitecture, with the main contents as follows:

1- Surveying, measuring and evaluating the status of environmental quality of the project area This is the "basis" data for comparison and evaluation the impact of the project on environment in the process of: implementation preparation, implementation of project components as well as bringing the project works into operation.

2- Analysing, assess impact on environment during the implementation of the Project, forecasting the positive and negative, direct and indirect, short-tenn and long-tenn impacts of the Project on physical environment (air, water, soil, noise), on natural resource (water resourceswater, land resources, biological, animal and botanical resources) and on economic-social environment (commwuty health .. econolluc and life activities)

3- Researching, proposing technical measures to minimize the disadvantage effects and find out the optimal method, which shall not only reduce adverse impacts hut also take full advantage of the Project's benefit when it comes into operation.

4- Developing program of environmental quality management, control and monitoring.

3.3. EIA methodology

The Report on Environmental impact assessment for the "Nha Trang Environmental Sanitation Project, Component 2, Phase 2" shall be made under the following methods:

- Statistical A-fethod: coHcct mctcorological, hydrological, rivcrs, cconomic-social data, reports and infonnation about annual environmental measurement data and the treatment ofthe collected data;

- Method of survey, take sample from site and analysis in laboratory those parameters about environmental quality in order to determine the parameters of current environmental situation;

- Method offast assessment: with the aim of calculating the pollution load based on pollution coefficient in each phase ofthe project;

- Method ofmodeling in the assessment of pollution spread in water environment: using mathematical models to evaluate and predict the spread and density of pollutants on receiving sources in the case that waste water has been treated to meet acceptable limits and where the WWTP has some problems, the waste water is not treated but directly discharges into receiving sources;

- Comparison method: is the method to assess environmental impact based on the system of current environmental standards and codes of the Ministry ofNatural Resources and Environment; and

- Method of economic-social investigation: investigate in the project area, the areas affected by the project; define the population situation and community awareness on environment as well as their ideas and recommendations for environmental safety during the project implementation.

Rept}" (ifEM, Lav;c C(lRsultant, January, 2011 6

Coastal Cities Environmental Sanitation Project (CCESP) - Pbase 2

Nha TranI{ City Sub-pr~;ect Component 2 Wastewater Treatment Plant

CHAPTER 1: BRIEF DESCRIPTION OF THE PROJECT

1.1. THE PROJECT

COASTAL CITIES ENVIRONMENTAL SANIT A nON PROJECT (CCESP) - NHA TRANG ENVIRONMENTAL SANIT A nON SUBPROJECT

PHASE 2 COAIPONEN'T 2

1.2. THE PROJECT OWNER

Tbe People's Committee of Kbanb Hoa Province

1.3. INTRODUCTION OF NHA TRANG ENVIRONMENTAL SANITATION SUBPROJECT

1.3.1. Subproject location

Nha Trang Environmental Sanitation Subproject (Nha Trang Subproject) under the Coastal Cities Environmental Sanitation Project covers three cities of Nha Trang, Dong Hoi and Quy Nhon. Nha Trang SUbproject Site is shown in Fig. 1-2.

1.3.1.1. The North WWTP

The location of the WWTP for the Northern Cai River is in the vicinity of Vinh Ngoc commune, to the West of Hon San. The area is situated between the railway and the main drainage canal (see Fig. 1-1).

Figure 1-1: Satellite map oftbe North WWTP

Reptlrl ofEIA, Lavic Ctmtiultant, January, 2011 7

Coastal Cities Environmental Sanitation Project (CCESP) - Pbase 2 Nha Trang City Sub-prqject Component 2 - Wastewater Treatment Plant

The treatment plant's area is about 3 ha that including a sanitation isolating buffer of about 7.3 ha. Wastewater after being processed will be discharged directly into Cai River through a canal system.

The Northern \\lWTP is located close to the concrete road of 6m width leading to Vinh Ngoc CommlUle People Committee's House. In the component 2, the assessing road of 150m from the commune road to .the northern WWTP has to implement in the Component 2.

1.3.1.2. The South WJJTP

The treatment plant is located close to Northern Hon Ong Sea Food Processing Industrial Zone, very close to Tac river bank. The area belongs to Phuoc Dong commune, Nha Trang City (see Fig. 1-3).

Figure 1-3: Satellite map ofSoutbern WWTP

The Southern WWTP is located at the North East ofNguyen Tat Thanh road; the distance of assessing road from the plant to Nguyen Tat Thanh road is about 3km and close KHATOCO Industrial Cluster.

1.3.2. Summary and des£ription of Component 2 - WWTP

1.3.2.1. Project capacity andphrasing

Based on the flow calculation, the WWfP is constructed in two phases with various

modules ofequivalent capacity. The capacity of individual treatment units includes:

The wastewater treatment plant in the North: 7,000 ml/day

The wastewater treatment plant in the South: 10,000 m3/day

RefHlrt (if ErA, Ltcv;/.: Consulttmt, January, 2011 9

- --------

--


Nha Trang City Sub-prqject Component 2 Wastewater Treatment Plant

Table 1-1: Capacity or Wastewater Treatment Plant - Component 2

Foul water ~ collection tank

Coarse & Fine r-+ screen Aerated Grit & r+Grease tanks

UnitItems Northern WWTP Southern WWTP

Capacity (Phase 1) m3/day 14,000. 40,000.._________L_~...___..~___.__..____.___,_ m3/dayCapacity (Phase 2) 21,000 60,000 ml/day 15,379 44,064

Daily average flow I m3/h 641 1,836 m3/dayMaximum flow in dry 23,155 65,664

season 1113,11 965 2,736 ml/dayMaximum flow in rainy 38,534 109,728

season m3/h 1,606 4,572 Source: FS Report, Nha Trang Environmental Sanitation Project (phase 2), Fichner, 2010.

1.3.2.2. Wastewater treatment technology

Both two plants use the same treatment technology that is deeply oxidation ditch, submersible air mixing device and aboveground stirring device (Rotor). This solution is suitable with maintenance condition and simple in operation.

ButTer tank

I

I

I

I

Sludge I

I ~ I

I

Aerated tank H Selector..' I , I Sludge acceptance '~-------------------LSlud~e

I Final sedimentation I

I tanks ~

+ISludge treatment I Chlorine contact Rivertanks

Figure 1-4: The flowchart or wastewater treatment technology

Figure 1-5: General designing orwastewater treatment technology

The components and equipments used for WWTPs are summarized as bellows:

Reptlrl tlfRIA, Ltwic Ct}n,t;"ltant, January, 2011 10



Table 1-2: Components and equipments used for wastewater treatment plant ------ _._-------------

No. Northern WWTP Southern WWTP

Equ.ipment Quantities Unit Capacity Amount Quantities Unit Capacity Amount

I J I Coarse 2 !m3/dayl 38,500 38,500 2 Im31day 109,500 109,500jscreen (30mm)

j 2 Fine screen (6mm) 2 1113/day 38,500 38,500 2 m3/day 109,500 J09,5001

3 Fine screen (4I11m) 2 m3/day 38,500 38,500 2 m3/day 109,500 109,500

4 Sand sedimentation 2 m3/day 38,500 38,500 2 m3/day 109,500 109,500 I tanks

1 5 Rectangular 2 m3/day 38,500 38,500 2 m3/day 109,500 109,500 aerated Grit

6 Grease tanks I m3/day 38,500 38,500 } 1113/day

7 Distribution I set 1 1 I set compartments

8 Regulation tanks 1 m3 1000 1000 2 m3

9 Mixing tanks 2 m3 70 140 4 m3

10 Biological tank 2 m3/day 23,200 23,200 4 1113/day

11 Final sedimentation 2 m3/day 23,200 23,200 4 m3/day tanks

12 Pumping 2+1 m3/h 500 1,000 4+2 m3/h

109,500 109,500

1 I

1000 2000

90 360

65,500 65,500

65,500 65,500

700 2,800

Source: FS Report, Nha Trang Environmental Sanitation Project (phase 2), Fichner, 2010.

Basic description of the technology is as follows:

JI Fine and coarse screen

The wastewater is led through pipe/canal into the receiving compartment installed in the WWTP. The receiving compartment conveys the wastewater through 2 distribution canals onto the surface offine screen to assure \\'a5tewater flow is distributed evenly on the surface.

The canals are closed and opened individually by penstocks. The screen includes two common waste conveyors and one waste press. The cleaning water will flow automatically into the combined drainage system and is pumped into the water distribution compartment at-the input of the treatment plant. Containers below the presses win receive cfeaned waste. Full containers can be moved and replaced by new empty containers.

21 Primary treatment (mechanical treatment)

The wastewater goes through pipe/canal into the receiving compartment installed in the WWTP. The receiving compartment conveys the wastewater through two distribution canals onto the surface of fine screen to assure wastewater flow is distributed evenly on the surface.

The canals are closed and opened individually by penstocks. The screen includes two common waste conveyors and one waste press. The cleaning water will flow automatically into the combined drainage system and will be pumped into the water distribution compartment at the input of the treatment plant. Containers below the presses will receive cleaned waste. Full containers can be removed and replaced by new empty containers.

31Aerated Grit and Grease Tanks

The wastewater enters the aerated grit removal tank. The grit tank aeration system consists of a series of air distribution pipes installed along the grit tanks. The air is delivered by rotary piston blowers. The air pipes are arranged along the wall in each tank to ensure that

ReptlrllJ/EIA, Lavic e,Jnsulta"t, January, 2011 11

Coastal Cities Environmental Sanitation Project (CCESP) - Pbase 2

Nha Trang City SuiJ..proiect Component 2 - Wastewater Treatment Plant

the water flowing through the tank starts to circulate cross scctional. drivcn by the rising air bubbles on one side and descending at the opposite wall. Thus, the wastewater spirals through the grit tank by moving forward. This motion enhances decisively the elimination of sand/grit from the wastewater. Each of the grit tanks can be isolated individually at the front end by penstocks. In case of a shutdown of one unit or during repair and maintenance works. the remaining units can take over the entire capacity for relevant treatment under normal flow conditions,

For the discharge of grit and grease. the tanks are equipped with scrapers operating alternating at the floor (removal of grit) or at the surface (removal of grease).

- Grit removal:

The grit settled on the bottom of the grit tank will be pumped by the scraper into two channels situated beside the grit tank. The grit slurry (grit-wastewater-mixture) from each grit collecting channel will flow through separate grit slurry pipes to the grit classifier installed in the Screens Building.

- Grease removal:

Grease, oil and other floating matter are forced into the lateral grease traps by the spiral motion of the wastewater stream. The fatty material floats to the surface of this latera1 compartment.

Grease is withdrawn discontinuously by the scum blades of the scraper from the surface into the separate grease collection tank. From there it will be pumped to the receiving truck for disposal.

- Air supply:

The air supply is provided by two blowers, which are generating the required air for aeration of each of the grit tanks. One blower is on stand.

4/ Regulation tank

Because the volume of wastewater from main pumping station to treatment plant is not constant, it is necessary to design the regulation tank.

In WWTP in the North, the regulation tank has capacity of 1000 m3 and installed with lift (step-up) pump (2+1), a pump is installed with frequency convertor. The capacity of each pump is about 500m3 !hour and the step·up height is about 2m.

In the treatment plant in the South, 2 tanks are built with capacity of each tank is 1000 m3

and installed with step-up pump (4+2), two pumps is installed with frequency convertor. The capacity of each pump is about 700m3 !hour and the step-up height is about 2m.

The tank is installed with overflow system! by-pass as well as underground mixing device.

5/ Mixing tank combined with flow distribution

The design of the station also includes mixing tank combined with the flow di&1ribution, reason to mix evenly the return sludge with wastewater. Especially it does make bacterium to be swelling; this will increase the settling ability of the sludge in the final sedimentation tank.

6/ Biological tank (Oxidation ditch)

- Operation:

For the perpetuation of horizontal flow as well as for proper mixing of the content of the basins submerged mixers mounted at the relevant locations of the basins will be installed.

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Nha Trang City Sub-pn~iect Component 2 - Wastewater Treatment Plant

For the intake of the necessary oxygcn, the aeration basins will be equipped with surface aerators (manulloth rotors) on the top ofeach basin ..

The oxygen intake for each of the Oxidation Ditches will be controlled by an adjustable weir at the outlet of the basins as well as by switching on-off of individual rotors.

The oval shaped concrete basins are separated by a partition in the middle of the basin dividing it in longitudinal direction. The wall rcaches up to the point whcre the concretc bends circularly on both sides. Thus the water reverses its' flows in this zone. It allows an internal re-circulating flow.

- The process otwastewater purification:

The sludge according to our design gains an age that categorizes it as a stabilized sludge. Thus, the sludge contains a wide variety of bacteria species for metabolizing carbon substrates.

The intense mixing of fresh aerated sludge (microorganisms) with incoming fresh wastewater triggers bio-flocculation (absorption of incoming wastewater constituents).

The Nitrogen compounds (for example N-NH4) will be oxidized in the aerated zones.

7/ Final sedimentation tank

7-J: Final sedimentation tank:

The activated sludge flows by gravity from the Activated Sludge Basins to the Final Sedimentation Tanks.

Two tanks operating in parallel will be foreseen in the North and four tanks in parallel for the South.

The Final Sedimentation Tanks are constructed as circular tanks with mechanical sludge removal. The activated sludge will enter the centre structure through a duct from below and will be distributed evenly to the clarification zone circumferencing the centre inlet structure. In the clarification zone the activated sludge settles, whereas the clarified water rises and overflows the weirs to the effluent channel and gravitates into a pit. The two tanks deliver their effluent into one pit. From this pit, the treated effluent flows to the Chlorine Contact Tank and onwards via the Outlet Mea


Nha Trang City Sub-prqject Component 2 - Wastewater Treatment Plant

Selector in front of the Activated Sludge Basins and the excess sludgc \\>ill be pumped to the Gravity Thickeners.

The return sludge pumps are designed for pumping of the max. Flow with two pumps for the North, respectively four pumps tor the South. The excess sludge pumps are designed tor pumping of the max. Flow with one pump for the North, respectively two pumps for the South.

During biological treatment, the bacteria maintain a specific growth rate: With the incoming wastewater, the content of suspended solids increases steadily.

The sludge return ratio can be adapted to a certain extent to the hydraulic load. This will be done by adjustable overflow weirs. The operation of the biological treatment must be controlled based on daily measurements of the sludge index in the plant laboratory.

More detail ofdeigns of tanks are shown figures in Annex.

1.3.2.3. Sludge Ireatmenllechnology

The process of sludge treatment includes: (1) Installation of Gravity Thickeners (sludge with 2

% DS after pre-thickening) and (2) Installation of Belt-Thickeners (sludge with 5 % DS after mechanical thickening). The block diagram ofsludge treatment is shown in Figure 1-6.

From wasfewafer freatment Excess sludge from secondary

sedimentation North 2,400 kg DS/d; 400m3/d; 0.6%

South 6,800 kg DSld; 1,133m3/d; 0.6%

~

From secptic tanks

Secptic sludge from secptic tanks North 160 kg DSJd; 26 m3/d; 0.6 % I South 600 kg DS/d; 100m3/d; 0.6 %

Pre-thickened sludge North 2,560 kgDSJd; 128m3/d; 2% I South 7.400kgDSJd; 37Om3/d; 2%

~

Pre-thickened sludge

North 2,560 kgDS/d; 128m Id; 2% ,

South 7.4OOkgDS/d; 37Om3/d; 2%

Gravlty-belt thickeners

Screw; Drum; Disc thickeners,

Centrifuge

Thickened slud~ North 2,560 kgDS/d; 51 m3/d; 5% I South 7,400 kgDS/d; 148 m3/d; 5%

4

Figure 1-6: Bloek diagram of sludge treatment solution

Both two plants are designed according to similar processes for sludge treatment.

Sludge from septic tanks is treated in the same technology and mixed with excess sludge from sludge acceptance tank.

Ri!JHJrl tJ/EM, Ltwie Cmlsultant, JIInUlny, 2011 14

Coastal Cities Environmental Sanitation Projed (CCESP) - Phase 2


- Septic sludge acceptance tank:

The septic sludge from the receiving trucks will have 0.5% to about 0.6% OS content.

The tank is sized for 10 truckloads per day, but will be steadily emptied into the inlet pipe system of the gravity thickeners by 2 (1 +1) pumps.

- Gravitational thickening ofexcess sludge:

For gravitational pre-thickening of sludge, cylindrical concrete tanks with a slow moving picket fence for sludge raking/scraping as well as mixing will be provided.

The gravity thickeners are suitable for thickening of biological excess sludge up to a dry solids concentration ofabout 2 to 3 %.

The pre-thickened sludge will be discharged directly into the Sludge Storage Tank.

- Thickened sludge acceptance tank:

Excess sludge concentration from gravitational thickener is approximately 2% OS. The prethickened sludge will be fed to the Gravity Belt Thickeners by positive displacement (eccentric screw) pumps will be uscd. 2 (1 +1) units with capacity of 8 m31h in the North and 2 (l+1) units with capacity of 15 m31h in the South will be installed.

- Mechanical thickening ofexcess sludge:

For mechanical sludge thickening a Gravity Belt Thickeners will be provided. The system operates with gravitational filtration on a moving belt. Polymer preparation and dosing stations prepare the adequate polymer.

Polymer is prepared as a solution of 0.5 % in strength by an automatic operating facility, consisting out of 1 storage bin for dry polymer, proportioning screw, wetting device, 1 preparation and ripening tank with agitator. The polymer solution is fed to the Gravity Belt Thickeners by pumps after passing a static inline mixer for dilution to about 0.05 % in strength. Post dilution is essential.

The Gravity Belt Thickeners are suitable for thickening the excess sludge up to a dry solids concentration of about 5 % after conditioning with a cationic polyelectrolyte which is fed upstream the thickeners into static mixers.

Oewatered sludge is discharged onto conveyor (including one hinge conveyor) leading to the container. After the container is filled, it is removed by truck to landfills for disposal.

- Recovery wastewater tank:

The tank recovers leaking wastewater and cleaning water. The water is pumped back to the tank. with capacity of 200 m31h for the plant in the North and 300 m31h for the South station.

Type of tank: RC rectangular tank with capacity of 500 m3

Number of tanks: 01 tank.

1.3.3. Total capital investment and operation schedule of Component 2

.:. Operation schedule ofthe component 2

The schedule of project implementation of WWTP is presented in following Table 1-3.

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Coastal Cities EDvironmeDtal SaDitatioD Project (CCESP) - phase 2 Nha Trang City Sub-project Component2 Wastewater Treatment Plant

Table 1-3: The Schedule of Project ImplemeDtatioD PlaDt

Source: FS Report, Nha Trang Environmental Sanitation Project (phase 2), Fichner, 2010.

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Coastal Cities Environmental Sanitation Project (CCESP) - phase 2

Nha Trang City Sub"p1'();ect Component 2- Wastewater Treatment Plant

.:. Capital investment

The capital investment of the component 2 is as follows:

Table 1-4: Summary of project cost ange ales: VNDlJSD 1/8 COOExch R I . = I , J

No Description I Total of Buget & other WB Fund/PHRD VN Fund • expenses

I Mill. VND MiII.USD Scale Mill. VND MiII.USD Scale Mill. VND IMiII.USD I

1 Land Acquisition 23,162 1.29 0% 0 .. 100% 23,162 1.29

! 2 I Construction and Civil Works 210,434 11.69 90% 189,390 10.52 10% ! 21,043 1.17 ! I 3 Goods and Services 238,769 13.26 100% 238,769 13.26 0% 0 ..

A Project Implementation 6,738 0.37 100% 6,738 0.37 0% 0 ..'t Management - -~----.--.-...-.~ - -. ---- -----

5 Consulting Services 22,460 1.25 100% 22,460 1.25 0% 0 ..

6 Training and Other Cost 4,860 0.27 100% 4,860 0.27 0% 0 ..

7 Taxes and Duties 52,818 2.93 0% .. 100% 52,818 2.93 8 Physical Contingency (10%) 44,920 2.50 95% 42,816 2.38 15% 6,596 0.37

9 Grand Total Costl 604,161 33.56 84% 505,033 28.06 16% 99,128 5.51

Source.' FS Report, Nha Trang Environmental Sanitation Project (phaye 2), Fichner, 2010.

Table 1-5: Investment plan for component 2 - Phase 2 WWTP North aDd South I i

I in Mill. USD in Mill. VND I

Total 2011 2012 2013 2014 Total 2011 2012, 2013 Treatment Plant North and South Construction and Civil Wolts

i E&M Equipment ' Compensation / Project lmp/ementaOOn Management Cost J Construction Supervision i TrainingIPhysical contingencies comp 2 I TaxesNAT 2.93

Total 33.56

Financial Conti cies 8.52

Total WWTP Incl. Fin. Can .42.08

11.69 I 2.34 13.261 0.00 1.29 ! 1.29 0.37 I 0.09 1.25\ 0.31 0.27 0.00 2.50 I 0.23

1,685 5,615 i 2,430

Source: FS Report, Nha Trang Errvironmental Sanitation Project (phase 2), Fichner, 2010.

I Note: not incl. financial contingencies.

Rt!ptlrl II/EJA, Llwit.' Cllnsuitant, January, 2011

20141

17


Nha Trang City Sub-pr(Jject Component 2 Wastewater Treatment Plant

CHAPTER 2: NATURAL, ENVIRONMENTAL AND SOCIO - ECONOMIC

CONDITIONS

2.1. NATURAL CONDITIONS

2.1.1. (ieotechnical and hydro-geological conditions

2.1.1.1. Geo-technical conditions

General geological characteristics ofNha Trang City are as follows:

a) The coastal area: most of the covering layers arc sand in which several areas havc thickness of 3m, followed by layers of clay with good pressure strength (R ~l kglcm2)

b) Hillside: includes layers in order:

- Medium crushed sand layer with R ~l Kg/cm2

- Carved stone and local coral layer, met at the depth of3 - 6.5 m, thickness of3 - 3.2 m

- Pebble and clay layer, encountered at depth of6.5 - 7.5 m, thickness of0.8 - 1 m

- Mixed clay layer, encountered at depth of 7-7.6 m, ending at depth ofS.8 - 9.0m

- Bedrock layer, encountered at depth ofS.S-9m, firm.

c) Low-lying area (western of the city, located at two sides of Quan Truong River): The area is usually flooded every year, terrain elevation is less than 1 meter, strata includes following layers:

- Top layer is gray white sand in soft plastic status, thickness from 1.5 to 2.5 m, this layer is widely distributed throughout the area.

- Next layer is a black clay sludge and shell layer in stretching status, thickness ofabout 7m.

- Under clay sludge layer is sludge layer, gray, stretching status, thickness of2.5 m

- At a depth of about 20m is yellow grey layer, semi-solid to solid status at depth of 20m to-25m.

2.1.1.2. Hydro-geologicalfeatures

Currently, Nha Trang City has large reserves of underground water; however, the water is mostly contaminated with salinity in coastal areas and at river outlets in eai and Quan Truong River.

According to the geological survey report ofPhase 1 and Phase 2 by VIWASE implemented in September 2005 and May 2009, the hydrological characteristics in the project area are summarized as follows:

• Tide:

Nha Trang City is close to Nha Trang Bay. Tidal regime in Nha Trang Bay is not even. According to observation data in Cau Do hydrological station in Khanh Hoa province, there are IS-20 diurnal tide days per month, time of rising tide is more than time of falling tide. Fluctuation water has relatively clear periodicity with the largest amplitude of 2.4 m; the average amplitude of tidal period is 1.2-2 m. Tidal water level ranges from -1.3 7 m to +1.03 m (VN2000 National Coordinate System).

Report (ifEIA, Lav;(' Ctmsultant, January, 2011 18



• Wave:

Maximum wave height was observed in the coast of Khanh Hoa provincal People's Committee office, which was 2.5 m (November 15, 1990). In Nha Trang Bay observable waves are greater than 2.0 m in height.

• River:

- Cai River (Nha Trang):

In many years, the average annual flow on Cai River in Dong Trang area with basin area of 1,244 km2 basin reaches 56.5 m3/s, corresponding to the module number of flow which is 45.5 I/slkm2 and total flows are 1.78 billion m3/year.

However, the annual flow variation in years is not great. Coefficient of variation (Cv) of annual flow is 0.37. Annual flow with frequency of75% is 41.3 ml/s or 1.3 billion m30fwater.

Flow in flood season: Annual flood of Cai River in Nha Trang starts from September to December (time maybe ditIerent a few weeks).

Flood peak discharge at peak Ha Ra - Xom Bong is as follow:

r

POlo 3 5 10

(m3/s) 4551 3692 3202 2446

Water levels measured in Nha Trang City are:

Hmax=2.05 m

Htb = 0.48 m

- Tae and Quan Truong River

Hydrological regime of the Quan Truong River directly affects the South of Nba Trang airport. It's just a branch of Cai River in Nba Trang; during the dry season there is no water, in the rainy season, water from Cai River in Nha Trang sweeps through adding with field water in Dien Khanh, concentrating and discharging into Be river outlet, Dong Bo river, causing flooding in two riverbanks.

According to the plan, Quan Truong River will be improved. stIaightened to go close to the expansion area ofthe city to the west to ensure flood discharging in part ofCai River to Be outlet.

• Flood:

In this area, there are often 2-5 floods each year, as mentioned above part of flood flow discharges to Tac River to go to Be outlet. High speed of flood on the river often causes serious flooding to low land. Submerged time can last 2-3 days. Historic floods in 1964 lasted for a week. The most dangerous case is when encountering wave combining 'with flood tide. In Nba Trang city, the most frequent flooded areas are Dien Khanh district and low areas such as: Vinh Thai. Vinh Ngoc, Vinh Hiep, Vinh Thanh, Vinh Phuoc, Vinh Hai and Ngoc Hiep Ward.

2.1.1.3. Topography

Topographic and geomorphic characteristics of Nba Trang City are generalized to three areas as follows:

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http:Hmax=2.05


Nha Trang City Sub-prq;ect Component 2 - Wastewater Treatment Plant

• The Northern ofCai River:

This area included the residential areas of Vinh Hai and Vinh Tho Ward, has relatively flat terrain with elevations from 3 m to 3.5 m; only the area near the end of emission station is low with elevation from 0.37m to 1.86m. This area is heavily affected by the flood from Hon Kho Mountain; this area is often flooded when it rains.

Residentia1 area in Vinh Tho. Vinh Phuoc ward has terrain along the pied of Hon Chong and Hon San Mountain so it is very slope with elevation from 5.1 m to 24m. Son Thuy residential area along Cai River has elevation from 0.5 m to 5.1 m.

• Central area:

The urban roads are flat terrain; elevation is from 3.9 m to 4.2 m.

Urban area to the west of Le Hong Phong street and Tac River through the western plain is lying terrain, elevation is from 0.5 m to 1.5m.

• Southern area:

Southern area is flat terrain; average elevation is from 2.4 to 3.5 m.

2.1.2. Climate

Nha Trang City has characteristics of tropical climate with two distinct rainy and dry

seasons.

2.1.2.1. Ail' temperature

With its mild climate, in the whole year, Nha Trang City has the summer which is lots of sunshine but not hot and the winter which is rainy but not cold. The details are as follows:

- Average annual temperature: 26.600C

- Minimum temperature: 14.60oC

- Maximum Temperature: 39.50oC

- Monthly average temperature: 28.40oC (June, July, August)

- Monthly average temperature: 24.30° C (January, December)

- The total amount ofheat during the year: 98,200oC

2.1.2.2. Rainfall

Rainfall varying from 1,000-1 ,500mm accounts for 51 %, rainfall under 1,000mm to 700mm accounts for 20%, the rest is rainfall from 1,50Omm to 2,500mm, in which the rainfall over 2,000 mm accounting for 12%.

- The average annual rainfall: 1,252mm and maximum: 1,061mm (November -1917)

- The highest annual rainfall: 2,552mm; lowest: 641mm

Rainfall is unevenly distributed in the year: 85% of rainfall concentrating in the rainy months (September to December).

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Nha Trang City Sub-project Component2 Wastewater Treatment Plant

2.1.2.3. Wind

Main prevailing wind direction in the year in Nha Trang City is North and Northeast. Southeast with average wind speed of 6m1s; dry heat Southwest wind appear less. Overall,

Nha Trang City is rarely affected by typhoons, cyclones.

Table 2-1: Wind speed in dominant directions (mfs)

Station Month

1 2 J 4 5 0 7 8 9 10 11 12

Nha Trang N NE NE SE SE SE SE SE SE NE N N

5.3 4.8 5.0 43 3.9 4.0 3.8 3.7 3.6 4.4 5.5 6.1

2.1.2.4. Moisture

A verage annual air moisture in Nha Trang City varies from 77% + 80%, the details are

shown in following table:

Table 2-2: Average monthly and annual air humidity at Nha Trang station (Ofc)

Year MOIIth

Yearly 1 2 3 4 5 6 7 8 9 10 11 12

2004 78 r 75 79 80 79 76 77 74 75 76 79 76 77

2005 77 81 80 80 76 76 74 78 84 80 84 79

2006 77 77 80 1

76 75 76 75 79 81 80 80 78

2007 i7s 76 80 80 81 78 78 80 81 84 83 79 80 2008 81 79 81 81 80 78

I 76 78 81 81 85 82 80

Source: Statistic yearbook ofNha Trang City. 2008.

2.1.2.5. Evaporation

Average annual evaporation is 3.2 mm/day equivalent to the annual rainfall, but focusing on

the dry months so the lack ofwater occurs in production and life.

Table 2-3: Total of monthly and annual evaporation capacity (mm)

Month Sta.tiOQ Total

1 2 J 4 5 6 7 8 9 10 11 12

Nha Trang 133 115 123 117 126 118 127 129 102 94 112 135 1.431

CamRanh 152 130 140 125 132 141 159 155 112 97 112 137 1.586

2.1.2.6. Solar radiation

Average annual hours of sWlShine in Nha Trang City in 2008 was 2,404.7 hours. Total of average daily sunshine hours is 6-7 hours. Variations of sunshine hours in months and years

in 2004-2008 are shown in the following table.

Reptlrt ofEIA, Luvic COllSultlmt, Jlmumy, 1011 21



Table 2-4: Average monthly and annual sunshine hour variation in Nha Trang station (%)

Month I Year

6 --t. Total 1 2 3 4 5 7 8 9 10 11 J2 j 2004

I . 249.5 ! 242.6181.7 248.7 I 211. 1 222.7 269.7 244.3 231.7 189.0 148.5 164.0 2603.5

2005 206.0 231.0 250.0 277.0 279.0 236.0 179.0 189.0 167.0 151.0 139.0 21.0 2325.0

2006 136.5 190.4 265.5 286.4 I 282.3 I 260.91 218.5 227.7 207.3 222.5 247.3 165.9 I 2711.2 2007 122.5 239.7 255.4 273.8 260.4 255.4 I 244.5 217.2 207.6 145.7 125.6 152.6 2500.4

I 2008 157.3 140.6 1234.9 271.3 265.5 284.9 262.7 . 239.4 1 162.2 I 206.1 I 78.8 82.0 , 2404.7 i Source: Statistic yearbook ofNha Trang City. 2008.

2.1.2.7. Typhoon

From 1976 to 2007, 11 hurricanes and one tropical depression landed on the territory of Khanh Hoa. The strongest wind intensity was level 6, level 7 (39-61 km/h) accoWlting for 55%; level 8,

level 9 (62-88Krn1h) accoWlts for 33%, level 10 (89-102 km/h) acCOWlts for 12%.

Table 2-5: Some features of typhoons in Khanh Hoa

Landing place

Time Strongest wind direction,· speed

(DlIs)

Total rainfall (mm)

Maximum daily rainfall ( mm)

CamRanh Nha Trang CamRanh Nha Trang CamRanh Nha Trang

KhanhHoa 14/10/81 3/11/78 23/10/92

20-8 20-NW 6-NE

26-W 24-W 20-E

98.5 345 222

133.3 246 103

98.5 345 130

2.1.3. Ecosystem

The project area has very limited flora and fauna due to the urban development in recent years. The non-urban areas are ·widely used for agricultural purposes, which are mainly rice fields, shrimp farms. In the hills. cashew and coconut are grown.

No indigenous animal and vegetable breeds do exist in the region. Nearby beach area is mostly sand or sludge and offshore dip slope. Most nearest coral reefs is about 15km from the coast including Hon Mun Marine Protected Area, which is the most diverse place on coral ofVietnam.

The number offish in Cai and Tac rivers decline sharply in recently years according to local fishermen due to the finishing and pollution from human activities. Over use of chemical, foodstuff for aqua farming cultivation, that effected water body quality.

2.2. SOCIO-ECONOMIC CONDITIONS

2.2.1. Economic development situation

Nha Trang is one key economic area in Khanh Hoa Procince, the economic growth of the city is relatively high. The average annual GDP increases 13.13% (2003 - 2007), trade services increases 15.54%, industrial output value increases 14.87%.

Total production value at current price of province in 2007 was 1,208.984.514 million VND. The details are shown in the following table:

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Nha Trang City Sub-prC?;ect Component 2 - Wastewater Treatment Plant

Table 2-6: Production value at current price of Nha Trang City divided by economic sectors in 2005 - 2007

No. Content 2005Economic sectors 2006 2007 I I Agriculture, Value (million I

361,276 I 438,003 I 452,003 I dong)

aquaculture

forestry,1

Rate (%) 0.07% 0.06% 0.04% Investment, Value (million

5,850,949 i 6,206,667 I

6,302,511VND)

industry

2 Iconstruction,

Rate (%) 1.14% 0.91% 0.52%

I Ii Value (million I

i 505,364,000 678,545,000 1,202,230,000Service, tourism 3 VND) Rate (%) 98.79% 99.03% 99.44%

Value (million 511,576,225 685,189,670 1,208,984,514VND)

Rate (%) Toal

100% 100%100% Source: Statistical Yearbook ofNha Trang City in, 2008.

2.2.1.1. Development ofindustry

In 2008, the value of industry production in Nha Trang is 6.672.540 million VND (by conversion price of 1994). Nha Trang has 2058 industrial establishments and small industries, with 31,396 employees, including state-owned enterprises. Nha Trang city has a share of 34.4% of the total value of industrial output across the province, mainly food industry, tobacco, textiles, clothing, leather dyeing, manufacture of metal products, wood appliances.

2.2.1.2. Development ofagriculture - forestry - aquaculture

- Agriculture: In first half of2009, the total area of the cultivation is 2,061 ha. Winter-spring rice areas in period of 2008 - 2009 are 750 and 720 hectares with average productivity of 59.6 quintals per hectare. In late 2008, the city has granted support of 40.5 tons of seed rice due to flood damage to the communes, wards for sowing of winter-spring season with a total value of 335 million VND.

- Fishery: the total fishing output is about 18,996 tons. For shrimp hatching, the farming area of shrimp consist of 200 ha with a productivity of 145 tons/year.

The agricultural production value of Nha Trang City in 2008 is 70,059 million VND, of which the cultivation production value accounts for 63.88%, followed by the livestock raising production value which accounts for 32.7% and the value of the agricultural service sector accounts for 3.42%, the details are shown in the following table:

Table 2-7: Production value of agriculture at current price ofNha Trang City

in period of 2004 - 2008 Unit: Million VND

&ector 2004 2005 2006 2007 2008 1. Cultivation 51,042 52,514 54,539 55,590 44,759

2. Livestock raising 34,207 13,865 13,418 13,862 22,931

3. Agricultural service 2,115 - 1,599 2.018 2,369 Total 87,364 66,379 69,556 71,470 70,059

Source: Statistical Yearbook ofNha Trang City in, 2008.

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Nha TranI{ City Sub-project Component 2 - Wastewater Treatment Plant

2.2.1.3. Tourism and sen/ices

Nha Trang is one of the popular tourist areas of the country and allover the world with famous landscapes: Nha Trang Beach, Vinpearl Land Bay, Thap Ba PoNagar, etc., which has become a highlight in tourism development, landscape conservation, contributing to economic development.

Tourism plays important role of major economic sectors in Nha Trang City, the tourism and service revenue dominates about 40% City's GDP. With nice and famous landscapes, the City attracts a huge tourists amount every years. In 2007, the total amount of tourists is 925.000 visitors, in which international tourists are 294.000 visitors. In 2008, due to effect of the global economic crisis, the amount of tourism visitors reduce, there are 776,000 visitors, in which the number of international tourists is 162,000 visitors. The total tourism revenue is 1,282,000 million VND and 773,704 million VND, respectively.

Hems 2005 2006 2007 2008

Tourism revenue (million VND) 505,364 678,545 1,202,230 1,282,000

2.2.1.4. Cultural works

Khanh Hoa province in general and Nha Trang City in particular has many valuable cuitural and historical works. Especially the Cham relics still exist in many parts of the city, notably Ba Ponagar tower located in the North of Xom Bong Bridge, Vinh Hai Ward, Nha Trang City. This is one of the largest Champa temples in the Central of Vietnam, which was built from 7th century to 12th century.

Long Son Pagoda at the foot of Trai Thuy Mountain is the largest Buddhist pagoda among more than 20 pagodas in Nha Trang, which was built in the 19th century.

In addition, Nha Trang has many cultural works, historical works such as Dong Bo War zone, Alexandre Yersin Relic, Tram Huong Tower, mountain church, and many other small temples, pagodas.

All cultural and historical works locate far from the project areas; therefore, there are no effects and damages to cultural and historical works in the area.

2.2.2. Social development situation

2.2.2.1. Population

By the end in 2008, the city has 19 wards and 8 communes and a total area of 252,596 km2, total population of 380,552 people, and average population density of 1,506 persons /km2• Total number of households is 83,220 households, on average of 4.5 persons per household. Average population of the City changed over the years from 2004 to 2008 which are shown in tables following:

Table 2-8: Average population ofNha Trang City 2004 - 2008

Year Population

(Eeople) In which

Female (people) Countryside (people) 2004 354,920 180,029 79,523 2005 358,175 181,546 80,193 2006 361,955 183,629 80,855 2007 366,647 185,481 82,607 2008 376,215 195,272 90,901

Source: Statistical Yearbook ofNha Trang City, 2008.

RepfJriO/EIA, Lavic ClJn.tfUltant, January, 2011 24



2.2.2.2. Culture

Nha Trang is a culture - society city. The authorities cooperate with the city's organizations and unions to conduct many information and communication activities, cultural activities, and sport tournaments to celebrate the important national days, anniversaries, political and economical events of the city. The City organized successfully the Ceremony of the Decision of Prime Minister on recognition ofNha Trang as a Grade I city directly under the prOVlllCC.

2.2.2.3. Education

There are 72 schools in Nha Trang City, including: 39 primary schools, 22 secondary schools, 01 secondary and high schools and 10 high schools with a total of 1,712 classes and 2,932 teachers and 63,673 pupils (2008).

2.2.2.4. Health service

In Nha Trang City, there are 04 hospitals; 06 local clinics. City maternity homes and 27 communes/wards medical stations. Infrastructure of the city's health sector is relatively good with large numbers ofhospital beds and medical and pharmaceutical staffs.

2.3. CURRENT SITUATION OF TECHNICAL INFRASTRUCTURES

2.3.1. Household sanitation

Currently the drainage system of Nha Trang has no sewers to collect wastewater and does not have an urban WWTP. Most households in the city have private toilets that account for 98.0010.

Table 2-9: Rate oftoilet types of households in Nha Trang City

Types of toHets Nha Tnm ~ (rate %) General Poor RrouP

Digging toilet --2.0One compartment toilet 3.3

Two compartment toilet 6.0 7.3 54.2Septic tank 46.1

Semi-septic tank 26.3 29.8 Absorbing and pouring toilet 8.0 9.4 Other 3.5 4.1 No toilet (Separate rate/total households and 2.0 3.2 poor house~

Table 2-10: Current situation of types of toilets ofhouseholds in Nha Trang City

Situation Rate(%} Normal 85.8 Blocking 7.5

ooded in rainy season 5.5 Stinking and polluted 3.8 Absorbed -Other 1.3

Most households have used septic tanks, but few of them have the habit of suctioning septic tanks. Furthermore, the building a septic tank sometimes is not properly, which does not ensure

Reptlrt tifEM, Lavic Ctlnsu/tllnt, January, 2011 25


Nha Trang City Sub-pr~iect Component 2 Wastewater Treatment Plant

sanitatio~ particularly, wastewater drainage from the toilets. Most households discharged wastewater into soil, infiltration wells (86.9010). According to a result of the investigation, percentage ofhouseholds, which connected to city sewer system, is only aoout 5.1 %.

2.3.2. Drainage system

The main sewer system had been built be1ure 1975 is about 1O,324m in length, that used the line ~ith width of 400mm -7 L800mm (mainly in the old city area: Phuong Sai. Van Thanh. Xuong Huan, Loc Tho ward). Until 1995, the city had been built around 6,41 Om of sewers, which mainly located on the route invested and managed by Ministry of Transportation (Road 2/4; Road 23/10; Le Hong Phong Street). Since 1995 until now, a series of culverts have been built with a total length of over 20,OOOm, of which type of sewers with d = 600800mm accounts for a large proportion. Therefore, the quality of the current drainage system (dmability, drainage capacity, leaking level, etc.) is still weak. The drainage system of run-off water and domestic wastewater are the same line and pollute the environment. Some hospitals in the city treated wastewater but it is not effective. At Tan Binh Industrial Zone, many factories have not treated wastewater but discharged directly into Quan Truong River. Together with the Cang Ca area, this Zone has created a polluted area.

The situation of encroaching river bank for housing, discharging an wastes into rivers causes the severe pollution as well as the most serious problems first in the Cai river and then followed by Kim Bong river (Phuong Sai ward).

Drainage system (including stonn water and wastewater) of the city is still limited and many residential areas also have to cope with flooding, especially in the rainy season. This can be seen through what the representatives ofhouseholds talk about the sewers in their residential areas:

Sewers Rate (%) 1. Unbuilt excavated land trench 15.8 2. Brick common sewer 33.2 3. City's sewer 5.4 4. Overflow seU:'absorb 48.4 5. Flow directly to pond/sea 1.1

From 2004 to present, the management of drainage system has been transferred to Khanh Hoa Water Supply Company (now known as Khanh Hoa Water Supply and Drainage Company) from the City Department of Urban Management.

The management unit in charge ofwater drainage systems is weak, which do not keep track ofculverts at present, and even there are many culverts that management unit does not know the size, flow direction, year built, etc. There is no equipment for the dredging of sewers; dredging works still manual.

2.3.3. Flooding and inundations

Nha Trang City only has stonn water drainage system with the limitation of capacity, the flooding and inundation sill happen in some areas of Nha Trang City, especially in rainy season. There is no wastewater drainage system, the dredging of drainage culverts and canals, etc. is very limited, the encroachment of residents and development of trees in some drainage ditches preventing traffic flow, accumulating of waste water causing pollutions and flooding after heavy rains.

ReptJrt ofEIA, Ltwic CIJII...·uitallt, Jalluary, 201 J 26



2.4. EXISTING ENVIRONMENTAL STATUS

2.4.1. Air environment

In order to evaluate the air environmental situation in project area.. the air samples are taken in the place where constructing WWTPs. 'I'he sampled locations are shown in Fig. 2-1.

Table 2~11: Analysis results ofambient air quality

I

NorthWWTP No. Parameters Unit

KK11 KK12 KK13

I Temperature °C 31.8 30.9 I "'"' ...>.>•.> 2 Humidity % 66.1 67.7 79.1

3 Wind speed mis 0.3 0.15 0.09

4 Suspended

rng/ru3 0.013 0.012 0.031dust

Dust PM 10 ! mg/m3 .5 (average 24h)

0.008 0.01 0.017

6 Lead dust

Mg/m3 0.03 0.04 0.073(average 24h)

7 CO rug/m3 11.8 12.7 12

8 N02 mg/m3 0.28 0.27 0.28

9 S02 mg/m3 0.08 0.1 0.148

10 H2S mg/m3 0.49 0.36 0.36

1 ] Instant noise dB 70.3 59.7 78

12 Vibration mls2 0.026 0.017 0.03

Source: RCAICE, HA U, 2009.

!:i.!!!LPosition ofsampling:

South WWTP

KK14 KK15 KK16

15.7 31.3 29.8

66.5 78.6 81.8

0.15 0.15 0.06

0.013 0.014 0.015

0.009 0.008 0.009

O.ot 0.065 0.061

8.2 13.6 10.5

0.25 0.38 .0.35

0.17 0.12 0.118

0.52 0.48 0.39

62.4 69.3 62.5

0.015 0.02 O.ot8

Allowable Applied limit standard

j ---

0.3 QCVN 05:2008

QCVNI 0.15 05:2008

1.5 QCVN 05:2008

30 QCVN 05:2008

0.2 QCVN 05:2008

0.35 QCVN 05:2008

0.42 QCVN 06:2008

75 TCVN

5949:1998

0.03 TCVN

6962:2001

I

KKl J: Residential area ofVinh Hai ward; KKJ4: Aquatic product processing industrial KK]2: Treatment plant of Vinh Ngoc; zone; KK13: Access road to treatment plant of KK]5: Nguyen Tat Thanh street; VinhNgoc; KK16: Southern treatment plant

Harmfol gasses: Through the results (see Table 2-11) shows that the environmental quality of air in project areas are relatively good, most hannful gases are less than allowed limitations (QCVN). Concentrations of S02 in some samples (KKll, KK14 and KK15) exceed the allowed limitations negligibly (only higher than standard 1.2 times at sample KK14). N02 concentrations in samples are slightly higher than that limitation. That causes vehicles and industrial machines operated in the certain monitoring time.

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Coastal Cities Environmental Sanitation Project (CCESP) - pbase 2

Nha TranK City Sub-prqject Component 2 Wastewater Treatment Plant

Dust: contented in the air environment is lower than allowed limitation due to no emission sources in the areas.

Noise: instant noise and vibration in the areas meet mostly in allowable limitations on noise in residential, administrative areas, hotels, trade, services alternated within 6 pm - 18h according to the TCVN 4949-1998. Only at location KK 13 (the road leading to the North WWTP) the instant noise value (78 dBA) lightly exceeds the allowed standard (75 dBA).In sumary, the air quality in the project areas has not changed in recent years and almost meets the permissible standards. That indicates that the air environment quality of the project areas is relatively good.

2.4.2. Water environment

.:. Surface water

The status of the surface water environment was assessed through analysis results of six typical samples taken in the project area as shown in the Table 2-12.

Table 2-12: Analysis results ofsurface water quality in the study area

SouthWWTP NorthWWTP No Target Unit

1 Temperature °C

2 pH

Total 3 suspended mg/I

solid (TSS)

4 00 mg/I

5 Oxidization mg 02/1(CODMn)

6 Coliform MPNil

7 BODs mg/I

8 Mn2+ mg/I

9 Total Fe mgll

10 NH4+ mgll

11 NOl ' mg/I

12 N02 ' mg/I

13 Total P mg/I

NMl NM5

30.0 30.15

7.51 7.53

92 91.6

3.71 2.83

35 43.5

3900 4100

21 26

0.126 0.103

1.45 1.26

2.76 0.75

27.4 13.3

0.039 0.067

0.0015 0.001

~

NMI0

30.14

7.31

78.8

3.42

40.4

3570

26.8

0.124

1.19

0.69

I 13.6

0.029

0.01

NM4

30.14

7.25

103

3.16

58

3520

29

0.104

1.56

0.89

14.8

0.093

0.002

------T----

NM6 NMll

30.13 30.2

7.57 7.42

92.4 79.1

3.56 3.51

46.9 39.6

3700 3490

29 27.1

0.128 0.016

1.38 1.15

0.79 0.72

12.9 11.3

0.083 0.053

0.01 0.0014

QCVN 08:20081

BTNMT(B2)

-5.5 t09

100

:;:2

50

1000

25

-

2

1

15

0.05

0.5


l:i!l1£: Location ofsampling: - NM2: Binh Tan bridge river water; - NM4: Cai River water near the North WWTP; - NM5: Tac River water in the west ofthe South Jt'WTP; - NM6: Shrimp pond near the North WWTP; - NA11D: Tac River water near the South WWTP; - NMll: Cai River water in the south ofthe North WWTP;

The results of surface water quality in the project areas shows that the surface water environment are relatively good.

Report (ifEM, Lavu: Consultillft, Je",uary, 2011 29


Nha Trang City Sub-project Component 1- Wastewater Treatment Plant

Concentration of TSS at sample N~ is slightly higher than VN standard due to the cleaning activities of shrimp fanus. Several parameters such as N02", BODs, N03' of some samples were higher than standard because domestic wastewater discharged directly into water body.

+:+ Underground water

The ground water samples are taken at 02 residential wells around the project areas. The analysis results ofenvironmental quality of ground water are sho\vn in following table.

Table 2-13: The analysis results of groundwater quality at pl'oject area

No I

Criteria I

Unit NN3 NN7 QCVN09:

I i 2008IBTNMT

1 . Temperature °c 30.2 30.1 2 pH 6.56 6.86 5.5 - 8.5

3 Hardness

mg!l 235 326 500(follow CaC03)

4 Total solid mgn 471 485 1500

! 5 As (III, V) mg/l 0.024 I 0.0167 0.05

6 Hg2+ mg/I 0.0008 0.6 0.001

7 Zn2+ mgll 0.51 2.12 3.0

8 cr mg/I 171 163 250 9 Cu mg/I 0.38 0.21 1.0

10 Pb2+ mg/I 0.0017 0.0061 0.01

11 Fe2+ mg/I 3.12 2.15 5

12 CoHfonn MPN/100ml 2 KPH 3 13 • Fecal Coli MPN/I00ml KPH KPH KPH

I


Note: QCVN 09:2008IBTNMT: National Technical Regulation on underground water quality.

- NN3: Well water at Ms. Nguyen Thi Thiep'sjami/y, 82145 Nguyen Khuyen, Vinh Hoi ward;

- NN7:Well water at Mr. Nguyen Van Toan - Le Hong Phong - Phuoc Long ward;

In comparison with the national technical regulation, all analytical parameters in underground water meet the requirement. This proves that the quality of underground water in the areas relatively good.

Report (IfEIA, Lavic C(m.~ultant, January, 2011 30


Nha TranI{ City Sub-project Component 2 - Wastewater Treatment Plant

CHAPTER 3: ALTERNATIVE ANALYSIS

3.1. WASTEWATER TREATMENT TECHNOLOGY

Project Consultants have suggested various technical options for consideration and comparison as follows:

Alternative 0 I: Bio Filter Reservoir - BFR

Alternative 02: Sequencing Biological Reaction - SBR

Alternative 03: Oxidation Ditch (shallow and deep) - OD

Alternative 04: Up-flow Oxidation Ditch Anaerobic Sludge Blanket - UASH

.:. Comparison criteria:

• Area demand

• Investment cost

• Operation cost

• Adaptation to changes of flow and loads

• Sustainabilityl Operation convenience

• Control and skills

• Reduction of P va N

• Available experience in Vietnam and Asian countries

Following table shows a summary and comparison of the criteria considered above:

Criteria BFR SBR OD UASB

Area requirements (ha)

North 13.90 14.69 16.93 15.07

South 14.60 17.06 23.40 16.44

Investment Cost per Im3/day (USD) (I) 831 937.7 888.23 1,052.47

Operation Costs (USD/y) (\) 96,700 153,100 888 1,052

Adaptability to changing flow

(load conditions)

Very good Modular layout Adaptable to different flow/load conditions

Moderate adaptable PLC controled sequences

I

Good Flexible in operation, depending on sludge returm operation (clarifiers)

Limited in change of flow conditions, good in increasing load changes

Sustainability/ease of operation

Filtration process, in house gallery for piping and equipment (easy accesable, small diameters), less measuring equipment. PLC controlled

Less flexible Dependent on control system, no manual operation possible. Needs IT skills for program use. Moderate use of measuring

Basically robust process, clarifiers need special attention. Moderate use of measunng equipment (level and O2). Little imported

Easy operation within layout limits, final clarifiers need attention, gas collection, storage, compression and enegy generation need skills

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Nha TranK City Sub-project Component 2 Wastewater Treatment Plant

BFR SBRCriteria on UASB equipment (level equipmentprocess, but can be !

operated manually, and O2), I j

. Controlled P+N INo PIN removal removal) Effluents (PlN P removal possible Controlled P+N

by chemical dosing removal has to be removal has to be Ipossible, requires into primary incorporated in secondary reactor, N·removal

incorporated in original layout. treatment phase

I requires separate original layout

Possible [0 upgrade (anoxic tank) denitrification Iuncontro1Jed P+N

Basically ,system

stage III existing because removal of Ianoxic and Ianaerobic conditions during settling and decanting i i

(/) Phase 1 North (10,000 mJ/day), direct costs, no contingencies, for comparison

.:. Alternative l'election:

These options have been submitted to Provincial relevant agencies, departments in October. Both domestic and foreign experts have reviewed and revised the Report, Option Alternative 03, Oxidation Ditch is final selection. This technology has the following advantages:

• Sustainable and simple

• Less imported equipment

• Adaptable to changing conditions offlow and load

• Lower investment cost

• Popular in Asian countries

• It was proposed and approved in the feasibility study (VIW ASE, 2005)

On November 9, 2009, the Provincial People's Committee approved this project proposal on WW1P. Both South and North WWTPs applied the same technology as deeply oxidation ditch that uses underneath air mixer and surface rotor system.

Wastewater will be transferred to coarse and fine screening system to remove solid wastes, then flow to grit tank and grease removal tank. In the tank, there is an aeration system containing a series of air distribution pipes installed along the grit tank's side. Rotary piston blowers supply air. Air pipes are arranged along each of the tank's wall, which ensures that when water flowing through the tank, it will start to circulate along the cross section, Waste water flow will be driven by the airflow which is generated by rising air bubbles on one side and descending at the opposite side. Thus, wastewater will flow spirally through the grit tank. This motion facilitates the elimination of sand/grit from wastewater. They be settled down on the bottom of the channe1 and will be collected by scrapers. Sludge in the channels is transferring to sludge treatment by the sludge-pumping pipes. Grease~ oil and other floating matters forced into the lateral grease traps. The scum blades of the scraper withdraw grease discontinuously from the surface into the separate grease collection tank. Then, sludge will be pump to the receiving truck for disposal.

Rt!ptlrl (ifEIA, Lav;c Ctlnsultant, January, 2011 32


Nha TranK City Sub-prqjecl Component 2 - Wastewater Treatment Plant

Because the following wastewatcr from the main pumping station to the WWTP is not regularly, thus, to ensure wastewater flow stably into the main treatment structures. Wastewater is pumped to the regulation tank before entering the mixing tank behind the oxidation ditch.

The sedimentation tanks are being construction as round tanks with mechanical sludge removal. The activated sludge will enter the centre structure through a bottom duct and will be distributed ev

;~ report environmental impact assessment...pr~iects; - decree no. 88/20071nd-cp dated may 28, 2007...

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