An Illustrated Guide to Basic SewagePurification Operations

Department of Water Affairs and ForestryFirst Edition, 2002

DEPARTMENT OF WATER AFFAIRS AND FORESTRY

A financial contribution to theimplementation of this project was made by the

Department for International Development,Southern Africa

Private Bag X313Pretoria0001

South AfricaTel (012) 299-9111

Copyright reserved

No part of this publication may bereproduced in any manner

without full acknowledgementof the source

ISBN 0-620-29884-7

This document should be sited as:

Department of Water AffairsAnd Forestry, 2002

This document was produced by:Department of Water Affairs and Forestry

Wates, Meiring & BarnardAnd illustrated by

Ilonka HaylettPO Box 2330, Cresta, 2118

FOREWORD

I

PREFACEWater services include water supply as well as appropriate sanitation. Servicesrefers to the provision of infrastructure as well as the sustainable operation andmaintenance of the associated systems. The Department of Water Affairs andForestry has an obligation to support municipalities with their constitutionalrole to provide water services to all citizens. One way in which the Departmentcan assist is by developing the skills of municipal staff. In this regard, theDepartment has identified the need to train on-site staff for the properoperation and maintenance of sewage works - essential components of manysanitation systems - and therefore developed this guide.

The first edition of this guide is aimed at entry grade attendants who operatesmaller waste water treatment facilities. Particular attention has been given tothe needs of those who have limited literacy skills. Important concepts andcorrect operational procedures have been explained in simple terms and in ahumorous manner by using cartoon illustrations. This guide emphasises theimportance of the operator’s job and providing services to communities.

This guide is part of a comprehensive support package to municipalities and fitsinto government’s endeavour to systematically build capacity at localgovernment level, providing well-structured and accredited training. It isintended as a reference for the personnel employed at a waste water treatmentfacility but can also be used by the facility manager for training purposes.

The participation of various persons in the development of this guide, their timeand knowledge sharing - is much appreciated.

Let’s all continue to work together to improve services to our communities.

Department of Water Affairs and Forestry

TABLE OF CONTENTS

Preface ................................................................................................ITable of Contents ................................................................................IIIntroduction ......................................................................................IIIOverview of Basic Sewage Purification Operation ..................................IV

1. Manual Operated Inlet Screen .......................................................12. Mechanical Operated Inlet Screen ................................................103. Grit Channel ...............................................................................144. Flow Measurement ....................................................................205. Anaerobic Ponds ........................................................................256. Settling Tanks .............................................................................297. Biological Filtration ......................................................................358. Activated Sludge .........................................................................419. Disinfection ................................................................................4610. Anaerobic Sludge Digestion ..........................................................5111. Sludge Drying Beds .....................................................................5512. Tertiary Treatment .....................................................................6013. Pump Station, Electrical Board & Store Room ................................63

Glossary1 English-Zulu..........................................................................71Glossary2 English-Xhosa.......................................................................73Glossary3 English-Swazi........................................................................75Glossary4 English-Sotho........................................................................77Glossary5 English-Tswana.....................................................................79Glossary6 English-Pedi..........................................................................81Glossary7 English-Tsonga......................................................................83Glossary8 English-Venda.......................................................................85Glossary9 English-Afrikaans...................................................................87

Preface ................................................................................................ITable of Contents ................................................................................IIIntroduction ......................................................................................IIIOverview of Basic Sewage Purification Operation ..................................IV

1. Manual Operated Inlet Screen .......................................................12. Mechanical Operated Inlet Screen ................................................103. Grit Channel ...............................................................................144. Flow Measurement ....................................................................205. Anaerobic Ponds ........................................................................256. Settling Tanks .............................................................................297. Biological Filtration ......................................................................358. Activated Sludge .........................................................................419. Disinfection ................................................................................4610. Anaerobic Sludge Digestion ..........................................................5111. Sludge Drying Beds .....................................................................5512. Tertiary Treatment .....................................................................6013. Pump Station, Electrical Board & Store Room ................................63

Glossary1 English-Zulu..........................................................................71Glossary2 English-Xhosa.......................................................................73Glossary3 English-Swazi........................................................................75Glossary4 English-Sotho........................................................................77Glossary5 English-Tswana.....................................................................79Glossary6 English-Pedi..........................................................................81Glossary7 English-Tsonga......................................................................83Glossary8 English-Venda.......................................................................85Glossary9 English-Afrikaans...................................................................87

II

SECTIONS

GLOSSARIES

INTRODUCTION

III

The purpose of this guide is to provide persons involved in conducting routinemaintenance tasks and checks on sewage treatment works with a betterunderstanding of basic sewage treatment operational activities.

The guide has been developed in an illustrated colour format to aid a widespectrum of users in the understanding of the underlying fundamentalconcepts to basic sewage treatment works.

- to apply the basic operating activities

related to a sewage treatment works effectively and to develop anunderstanding why these tasks are important in the overall functioning of theworks.

- to provide guidance in basic sewage treatment

operations to staff.

- to develop an understanding of routine operation and maintenance

activities of a sewage treatment works.

The guide is intended for use by:

Water care operators and attendants

Water care managers

Educators

!

Correct action

Incorrect action

Trouble or problem

You will see the following symbols in the manual:

VI

Manual Operated Inlet Screen 1

Manual Operated Inlet Screen 1

1

Isisefo lapho kusetsenziswa khona I harika yesandlaIsefo esentjenziswa iharika yesandla

Sisefo lapho kusetshentiswa iharika yesandlaSefo eo ho sebedisoang haraka ea letsoho

Sefo e e dirisang haraka ya seatlaSefo e e somiswago ka haraka ya seatla

I sefo leyi yi tirisiwaka ihareka hi mavokoSefo ine ha shumiswa haraga ya tshanda

Inlaatwerke handrooster

^^

The Manual Operated Inlet Screen Unit

Inlet chamber

Inlet opening

Platform withdraining holes

Screening bars

START OF THE DAY SHIFT The operator arrives at workwearing his own clothes and shoes

The operator changes into the correct work clothes andshoes

2

The Purpose of the manual operated inlet screen

Screening of the incoming raw waste water is part of the preliminary treatmentphase and is applied to remove floating objects. Thepurpose is to protect mechanical equipment in downstream process units andto reduce blockages in pipes, channels and sumps. In addition, floatingmaterial can encourage the development of odours and fly breeding.

non-biodegradable

Village

Manual Operated Inlet Screen 1

CHANGINGROOM

SEWAGEWORKS

Operator arrives at work - this procedure is the same for all operators

TO GRIT CHANNEL

Wheelbarrow Lime

Bucket

Rake

SpadeWork clothes

Gloves

Rubber boots

BUTTON UP!!!

The operator with the correct work clothing, gloves andboots

The operator with the correct tools and equipment

The operator must use the correct rake with tinesthat fit snugly between the bars

3

Example of a rake that is not suitable for the work,the tines do not fit between the bars

The operator can use a wire hook to removematerial which is stuck between the bars

Notes...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

Manual Operated Inlet Screen 1

The rake

No pets are allowed at theworks - the INLET DOGis included toget your attention

The rake

ToolsCorrect clothing

Lime

1. The operator places the rake with the tines between thebars. 2. He rakes with continuous up and down movementfrom the bottom to the top of the bars. 3. The collectedmaterial is then moved to the top, on the platform to drainand dry

The operator sprinkles lime on thedrying screened material to discourage flies

Do not pull the screenable material over into thegrit channel

Do not wash screenings off with a water jet, itforces the residue through the bars into thedownstream units

Notes ..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

4

Manual Operated Inlet Screen 1

Work procedure

Screenable materialpassing throughscreens

12

3

Sewage Works

5!

Screenable material has been allowed to build up andforces sewage back through the pipes into the manholesin the community

The operator must not allow screenable materialto build up in the inlet chamber

Build-up of screenable material forces sewage backinto the manholes in the community and forces materialthrough the bars and into the downstream units

Problems caused by screenable material accumulation atthe inlet works include unpleasant odours and possiblehealth problems in the community and at the works

Other problems at the plant include pipe blockages,scum formation and screenable material will occupyprocess volume in downstream units

!

!

!

Manual Operated Inlet Screens 1

Village

A build-up of material at the screens

Supervis

or

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6

!

The operator checks the colour of the inflow The operator calls the supervisor if the inflow is not theusual colour

The operator checks to see that there is inflow intothe inlet chamber

The operator calls the supervisor if there is no inflow

The community can also be responsible for blockagesand no inflow into the sewage works by dumpinggarbage and other materials in the manholes. The lidmust always be on the manhole

The community should not dump anything in themanhole. It leads to problems in the community andat the sewage works

Village

Sewage Works

Manual Operated Inlet Screens 1

!

oil

VillageProblems with the inflow

Notes ..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

7

The operator should not eat or drink near theinlet works

Unhygienic practices can lead to illness

Before eating or drinking and after each cleaningcycle, the operator should wash hands with soapand water

The operator must eat and drink in designated areas

Manual Operated Inlet Screens 1

Safety tip - do not eat near the inlet works

BATHROOMEATINGROOM

SOAP