Quy trình vận hành nhà máy xử lý nước thải Volume 1 eng (done)

The proposed new treatment works comprise of new river debris removal systems, grit chambers, 25mm coarse screens, main inlet pumping stations, 6mm fine screens, grit and grease removal

TABLE OF CONTENT

1 INTRODUCTION 4

2 SYSTEM DESCRIPTION 6

2.1 Design Criteria – 6

2.2 Process Description 6

3 SYSTEM OVERVIEW AND FLOW SCHEMATICS 9

3.1 System Overview and Flow Schematics 9

4 HEALTH AND SAFETY 36

4.1 Mechanical Hazards 36

4.2 Electrical Hazards 37

4.3 Falling Hazards 37

4.4 Chemical Hazards 37

4.5 Gas Hazards 37

4.6 Noise Pollution 38

4.7 Odour Pollution 38

4.8 Infection Hazards 39

4.9 Fire Hazard 40

4.10 Basic Health Measures 40

1.1 GENERAL PLANT SAFETY 40

5 PERSONNEL 42

5.1 O&M Personnel 42

5.2 Personal Responsibiliies 51

6 SEWAGE QUALITY SAMPLING AND TESTING 53

6.1 Process Control & Laboratory Testing 59

6.3 Laboratory Safety 67

7 ELECTRICAL AND SCADA SYSTEM 69

7.1 SCADA SYSTEMS 69

7.2 ELECTRICAL SYSTEM 90

LIST OF APPREVIATION

1 Introduction

The objective of this operation and maintenance (O&M) manual is to contribute to the objective of implementing new sanitation facilities for sewage flowing from rivers / canals to Yen So Park of Hanoi This O&M manual covers primarily the facility for treatment of the wastewater that is collected from Kim Nguu River, Set River and future sewer network from Yen So Park Development The proper use of this manual together with sufficient resources (manpower and annual operation budget) will help to ensure the following:

 compliance of the effluent quality according to Vietnamese standards

 cost-efficient operation of the facility

 sustainable maintenance of the facility

 proper health and safety for employees

The manual is a guiding tool in the operation of the facilities It gives explanations about:

 the process design

 the design of the individual parts of the facilities

 procedures for operating the facilities

 procedures for servicing and maintaining the facilities

 procedures for monitoring the performance of the facility

 Personnel requirement

Further the manual includes suppliers‟ technical documentation, which gives more detailed and precise explanations about maintenance and safety which are specific to the equipment

The O&M manual is divided into following volumes:

 Volume 1 provides an introduction and general overview of the system, the personnel requirements, and safety procedures to be implemented

 Volume 2A describes Yen So liquid line and STP equipment, operation and its routine preventative maintenance

 Volume 2B describes Yen So Solid line and STP equipment, operation and its routine preventative maintenance

 Volume 3 contains equipment O&M manuals and data sheets that supplement the information from the suppliers about equipment maintenance Inspection records for each piece of equipment are included The basic understanding of the system and its design provided in this O&M manual will assist facility personnel

in coping with different conditions as they occur This O&M manual describes the most probable operating conditions at the facility; however, conditions not described here can occur Therefore, it will be necessary to amend these procedures as different conditions are encountered during the operation of the Yen So STP O&M personnel should use industry standards and manufacturer‟s literature to supplement the operating instructions and procedures described in the following volumes The manual is bound in such a manner to facilitate this updating

This manual should remain on site and be located in a place that is easily accessible to operating and

2 System Description

2.1 Design Criteria –

2.1.1 Design Flow and Loads – Yen So Sewage Treatment Plant is designed to treat a maximum of 200,000

m3/day with following consideration

Average dry weather flow 200,000m3/d

2.1.2 Design Wastewater Characteristics

2.1.2.1 STP Wastewater Influent Characteristics–

2.2 Process Description

The project is for the design and build of a new Sewage Treatment Plant (STP) at Yen So Park located in Hanoi, Vietnam The proposed new treatment works comprise of new river debris removal systems, grit chambers, 25mm coarse screens, main inlet pumping stations, 6mm fine screens, grit and grease removal tanks, sequential batch

Column A

facilities, gravity belt thickeners, sludge digesters, gas holders, centrifuge dewaterers, odour removal systems, polyelectrolyte dosing systems, carbon dosing system and alkalinity dosing system

The Sewage Treatment Plant at Yen So Park receives flows from Kim Nguu River, Set River and the future sewerage network from the Yen So development The works is designed to treat a maximum of 200,000 m3/ day with a peak hourly flowrate of 2.1 times this Inlet System is protected by a log boom (from floating debris) which diver the debris to a debris removal system mounted on the bank of river Floating debris is removed and collected in skip for disposal The river level is raised by two sets of radial weir gate mounted in the river The flow to treatment passes through river intake screens mounted in the riverbank; three for Kim Nguu and two for Set Screenings are collected and disposed of in skips Each screen can be isolated by wall mounted actuated penstocks After river screening, the flow passes to two sets of two number grit chambers Grit is removed and is classified prior to disposal to skips for removal The liquor from the grit classifiers is returned to the common inlet channel and each grit chamber can be isolated by wall-mounted penstocks

After grit removal, the flow is piped to the main inlet pumping stations where it passes through 25mm coarse screens The Kim Nguu river flow passes through three parallel screens and Set river flow passes through two screens The Kim Nguu flow will in future be augmented by a further flow from the Yen So development Each screen is channel mounted and complete with actuated isolation penstocks and emergency bypass hand raked screens

After coarse screening, each river stream is pumped via dedicated main inlet pumping stations (MIPS) to the combined 6mm fine screening stage Kim Nguu and Set River pump stations each comprise of 6 No fixed speed submersible pumps operating on 4 No duty and 2 No standby configuration

The combined fine screen process includes 4 parallel channel mounted 6mm screens and an emergency bypass hand raked screen Each screen can be isolated by actuated penstocks The screenings are transferred to a skip for disposal

Following fine screening, the combined flow passes to a grit/ grease removal stage There are four grit/ grease removal tanks Grit is removed from the front hopper of the tank by dedicated grit pumps and pumped to 2 No grit classifiers Grit is disposed via skip and effluent drained to the Kim Nguu main inlet pump station Grease is floated by air to the surface of the tank and removed by scraper to an outlet hopper for removal by skip The air is introduced to the base of the tank via a common header supplied by four number air blowers

After the grit/ grease removal tanks, the flow gravitates to the sequential batch reactor (SBR) basins There are eight treatment basins operating in two modules The SBR basins in each module will treat sewage in batches, with the operation of basins staggered to allow continuous acceptance of sewage and continuous discharge of effluent Each SBR basin inlet can be isolated by actuated weir penstocks

Each SBR undergoes a treatment cycle that consists of the fill, react, settle and decant sequences During the fill sequence, the SBR basin is filled with untreated sewage Once the SBR basin is filled, aeration commences which

is known as the react sequence After the treatment process is complete, the aeration is stopped and biomass will

be allowed to settle to the bottom of the tanks (settle sequence) When the biomass has settled, a layer of clear treated water at the top of the SBR basin is removed by two decanters during the decant sequence

Each SBR module has 6 No air blowers, operating in a 4 No duty and 2 No standby configuration Excess biomass from each of the SBR basins is removed during the settle sequence by 2 No waste activated sludge (WAS) pumps and directed to the sludge holding tanks Return activated sludge (RAS) is returned to the bioselectors for simultaneous nitrification denitrification and enhanced biological phosphorus removal by 2 no RAS pumps A carbon dosing system and alkalinity dosing system are provided and doses upstream of the SBR basins for adjustment of nutrient and alkalinity levels in the influent

About third of treated effluent from the SBR basins is channelled into UV disinfection units and the remaining treated effluent from the SBR basins is discharged back into the Kim Nguu River After UV disinfection, 3,000m3/ d of the treated effluent undergoes tertiary treatment before being recycled for plant usage Tertiary treatment comprises 2 No hollow fibre membrane filtration (HFMS) units operating in parallel The remaining water after UV disinfection shall be discharged directly into the Yen So Lake

Sludge holding tanks are provided to store the SBR waste sludge From the sludge holding tanks, the sludge is transferred to 4 No gravity belt thickeners for thickening process Sludge is fed into a static flocculator tank by means of 6 No thickener feed progressive cavity pumps (4 duty/ 2 standby) Polymer is dosed into the sludge prior to the thickeners to flocculate fine particles Filtrate produced from the sludge thickeners will flow to the Kim Nguu main inlet pump station

The thickened sludge from the sludge thickeners is stored in the 2 No thickened sludge storage tanks to allow a continuous flow to the sludge digesters A macerator is installed in each of the thickened sludge holding tank outlet to macerate any solids left in the sludge before being fed to the sludge digester The thickened sludge is fed

to 2 No anaerobic digesters to reduce the thickened sludge volatile suspended solids content The gas generated

by the digesters is stored in 2 No double membrane type gas holders Part of the gas shall be used to mix the sludge in the digesters, part of the gas shall be used for the heating of digester sludge and the excess gas shall be flared off

The digested sludge gravitates to the 2 No digested sludge storage tanks Digested sludge will be fed to 4 No centrifuge dewaterers to dewater the digested sludge via 6 No fixed speed progressive cavity dewaterer feed pumps (4 duty/2 standby) The sludge cake is conveyed to sludge storage area and transfer to skips for disposal off site Centrate from the dewatering units will flow to the works liquor tank

Polymer is dosed into the sludge prior to the dewaterers to flocculate fine particles to increase dewatering efficiency.The polymer dosing system is designed to accept powder supply Powdered dry polymer is stored in big bags and is transferred to a hopper The hopper discharges into the powder feeder that feeds the polymer mixing tank Service water from the service water booster pumps is added to the polymer mixing tank to make up the polymer solution Polymer solution is drawn from the storage tank by 4 No dosing pumps and is dosed into each thickener feed pump delivery There are separate polymer dosing systems provided for the thickening and dewatering plant

Filtrate from sludge dewatering centrifuges gravitates into the filtrate holding tank before being fed to the Filtrate Sequential Batch Reactors (FSBRs) A bypass shall be provided from this holding tank back to manhole MH26B from where filtrate could be returned directly to the main SBR process in case that the FSBRs are only partially or not operational during maintenance activities, or in case that the influent sewage and operational conditions do not require utilisation of the FSBRs

Potentially odorous air is drawn from the main inlet pumping stations, coarse screens, 6mm screens, grit and grease removal tanks, grit handling plant, works liquor tank, sludge holding tanks, sludge thickening units, thickened sludge holding tank, digested sludge storage tank, sludge dewatering units, collection skip for Kim Nguu and Set River debris removal to 4 No odour control facilities

3 System Overview and Flow Schematics

3.1 System Overview and Flow Schematics

Sewage treatment plant using Sequence Batch Reactor (SBR) including:

Process Flow Diagram

3.1.1 Intake Works

The Sewage Treatment Plant (STP) at Yen So Park receives flows from both the Kim Nguu and Set rivers Each river intake system is protected by a log boom and debris removal system to prevent any floating debris entering the inlet works

The trapped debris is directed towards a diversion channel mounted on the side of the riverbank The debris

is removed by a mechanical 50mm screen which is cleared by a motor driven rake upon detection of high differential level The debris is deposited into a skip via a screenings conveyor The Kim Nguu debris removal area is connected to odour control unit 3 The Set debris removal area is connected to odour control unit 4 The debris removal systems can be isolated by stop logs

The level in the river is maintained by two sets of 2 No radial weir gates mounted downstream of the log boom and a level transmitter The radial weir gates can be isolated by stop logs

Yen So STP- Flow to Inlet Works

3.1.2 Inlet Chamber

Incoming flow from the Kim Nguu River and Set River flows into the intake screens Each screen channel has a motorised inlet and outlet penstock The screens are cleared by a motor driven rake upon detection of high differential level measured by a level transmitter The screenings are deposited via a screw conveyor compactor into a skip

Inlet Chamber for Kim Nguu

3.1.3 Grit Chambers

The influent from the Kim Nguu and Set River intake screens gravitate through the underground pipe to 2nos

Of grit chambers the Kim Nguu grit chambers and Set River grit chamber respectively Both grit chambers trap readily settable sand and grit in the hoppers The trapped sand and grit is removed from the hoppers by Duty/Standby grit pumps, and processed by Duty/Standby grit classifiers The classified grit is disposed off-site and the remaining water will return to the common grit chamber inlet channel

The Kim Nguu and Set River grit chambers can be isolated by inlet and outlet penstocks

Flow from the Grit removal chambers gravitate to the inlet of the Main Inlet Pumping Station

Kim Nguu Grit Chamber

3.1.4 Kim Nguu Coarse Screens

Flow from Kim Nguu grit chamber gravitates to Kim Nguu Inlet Chamber Coarse Screens and combined with sewerage from Yen So Development, where it passes through 25mm coarse screens in order to protect sewage submersible pumps from debris

Return liquor from rejected flow from hollow fiber membrane system, drain flow from odor control unit 1, drain flow from odour control unit 2, emergency overflow from digested sludge tank, emergency overflow from thickened sludge tanks, emergency overflow from sludge holding tank, flow from thickener filtrate, grit classifier drainage, drainage from grit grease removal tanks, drainage from odour control unit 3, and flow from filtrate holding tanks gravitate back to main inlet pumping station through manhole No.30 before the flow passes to the coarse screens The return liquor will not be considered during the initial operation

There are 3 no automatic coarse screens, and two manual screens Each screen channel can be isolated by inlet and outlet penstocks, screening screw conveyor and compactor carry the screenings into skips

The coarse screens are connected to odour control unit 1

3.1.5 Set River Coarse Screens

Incoming flow from Set River grit chambers flows to 2 No 25mm coarse screens The sewage passes through

Grit Pumps

Grit Classifiers

Each screen channel can be isolated by an inlet and outlet penstocks The screenings are deposited via screw conveyor compactor into skip The coarse screens are connected to odour control unit 1

Flow to Main Inlet Pumping Station

3.1.6 Main Inlet Pumping Station

Sewage from Kim Nguu and Set River coarse screens flow to the main inlet pumping station, for pumping to 6mm fine screens in the preliminary treatment works.The pumps in the main inlet pumping station lift the sewage to a level in the preliminary treatment works that allows it flow to gravitate through the whole plant Main inlet pumping station is separated into 2 nos of pumping stations for Kim Nguu & Set River flows Both stations are protected by automatic and manual raked standby 25mm coarse screens The screenings are deposited via 2 stages screw conveyor compactor into skips

Kim Nguu and Set River pumping stations contains six nos submersible pumps each For each pumping station, 4 pumps are duty and two pumps are standby The sewage flow splits into two halves in the wet wells, and each well containing 3nos fixed speed submersible pumps Pumped flows are subject to in-pipe flow measurements

Kim Nguu and Set pumping stations are odour controlled

Kim Nguu-Set River Coarse Screens

3.1.7 Preliminary Treatment Works

 Fine 6mm screens + wash-compactors

 Combined aerated grit + grease removal

 Separated grease automatically scraped into skips

 Grit pumped to classifier and loaded to skips

Preliminary Treatment Works General Layout

Preliminary Treatment Works:

Preliminary treatment consists of temporarily holding the sewage in a quiescent basin where heavy solids can settle to the bottom while oil, grease and lighter solids float to the surface The settled and floating materials are

3.1.7.1 Fine Screen:

Sewage from main inlet pumping station is pumped to fine screens inlet chamber, before passing through 6mm fine screen, prior entering to the 4 numbers of grit/grease removal channels The purpose of the fine screens is to remove small objects that escape from coarse screens in order to protect downstream equipments There are four fine screens running as three duty and one standby, beside one emergency manual fine screen All fine screens can

be isolated by penstocks located up-stream and downstream

Manual Fine Screen

3.1.7.2 Grit Grease Removal System:

Grit and Grease Removal System is designed to reduce horizontal flow velocity to allow heavy particles to settle while grease and other floating substances are allowed to rise to the surface to be separated The removal of grit and grease elements is important to the durability of downstream equipment, parts, bearings, etc In addition to grease and grit removal, the system also contributes to the reduction of BOD and TSS

There are four Grit Grease removal channels which are equipped with mechanically driven travelling bridge type

of grit scrapers that continually drive the collected sludge towards a hopper in the base of the tank where it is pumped to grit classifier Grease and oil from the materials float to the surface where they are removed by skimmers and chute out to grease skip tanks

An aeration system is utilized to keep the majority of organic materials in suspension during this process A slower spiral flow at the effluent end allows grease to float to the top of the unit for easy removal The aeration system consists of blowers, air pipes and diffuser system that cause the grease to coalesce Grease is trapped behind the baffle boards and scraped into the grease sump by the grease scraper to chute to skip grease tank

Mechanical Fine Screen

3.1.8 Sequential Batch Reactor (SBR)

Flow from the grit/ grease removal tanks is split between two SBR modules, each consist of 4 No treatment basins

Each SBR basin contains aeration system (Blowers, air pipes and air diffusers), waste sludge system (WAS pumps and WAS pipes), sludge recirculation system (RAS pumps and pipes) and surface skimming decanter The purpose of SBR basins is to remove BOD, reduce suspended solid and reduce nitrates A comprehensive description regarding their system provide in volume 2A

Flow to Sequential Batch Reactors

SBR Aeration System

Air Diffusers

Air pipes Air Blowers

Blower Cooling System

SBR Aeration and Dosing System

Sludge Wasting System

Sludge Recirculation System

WAS Pumps

WAS Pipes

RAS Pipes RAS Pumps

WAS Pipes

3.1.9 UV Disinfection

67,000m3/ d of the treated flow from the SBR basins gravitates to the 2 No duty UV units for disinfection The remaining effluent from the SBR plant will gravitate to a discharge point in the Kim Nguu River to the east of the site

Kim Nguu Discharge

UV Plant

SBR effluent discharge, and UV discharge

3.1.10 Ultra Filtration Membrane Treatment Plant

After the UV disinfection, approximately 3,000m3/ d of the treated effluent undergoes further tertiary treatment before being recycled for plant use 3 No membrane plant feed pumps transfer the treated effluent to the membrane plant for tertiary treatment

Effluent after tertiary treatment gravitates into the service water sump where it is drawn by 3 No fixed speed centrifugal pumps and be used as the process water This process water pumped to odour control units 1, 2 & 3, dewaterer polymer dosing plant, thickener polymer dosing plant, sludge dewatering units, membrane chemical cleaning plant, Kim Nguu grit chamber, thickener washwater pumps, site hydrants and hose points

Memberane Treatment Plant

3.1.11 Sludge Holding Tanks

Waste activated sludge (WAS) from the SBR basins is transferred to the 2 No sludge holding tanks The WAS is

pumped to the sludge holding tanks by WAS pumps From the sludge holding tanks, the sludge is pumped to the

thickener units by using 6 No variable speed thickener feed pumps

RAS Pumps

Thickener Feed Pumps 3.1.12 Sludge Thickener

Sludge from the thickener feed pumps enters 4 No gravity belt thickener units Each thickener unit is controlled

by a local control panel

Each thickener unit consists of a flocculator tank and fixed speed main drive which rotates the belt

3.1.13 Polymer Dosing

The polymer dosing system is designed to accept powder supply Powdered dry polymer is stored in big bags and

is transferred to a hopper The hopper discharges into the powder feeder that feeds the polymer mixing tank Service water from the service water booster pumps is added to the polymer mixing tank to make up the polymer solution Polymer solution is drawn from the storage tank by 4 No dosing pumps and is dosed into each thickener feed pump delivery There are separate polymer dosing systems provided for both the thickening and dewatering plant

Polymer Dosing System 3.1.14 Sludge Digesters

Thickened sludge from the thickening units is transferred to the 2 No thickened sludge holding tanks From the thickened sludge holding tanks, the sludge is pumped to the 2 No sludge digesters by digester feed pumps Sludge is held in the 2 No digesters at 35-37°C under anaerobic conditions to allow digestion of sludge solids Biogass produced by the digestion process is removed from the top of digester, a proportion of the biogas is drawn off the biogas main to the gas mixing compressors The surplus biogass is store in gas holders

Incoming sludge is colder than the operating temperature range and therefore needs to be heated up Biogas produced by the digesters is used as fuel to heat the thickened sludge Hot water from 2 No boilers is used as a heating medium to heat up recirculated sludge via a heat exchanger Each digester is equipped with one heat exchanger

Digested sludge overflows from the digester and gravitates to the digested sludge storage tanks

Sludge Digesters

3.1.14.1 Digester sludge recirculation pumps

Sludge from the digester will be recalculated through a heat exchanger to ensure close temperature control

of the digester contents Two sets of 2 No variable speed sludge recirculation pumps are used and operated on a duty/standby basis for each digester

3.1.14.2 Hot Water Pumps

The digesters are maintained at 35-37°C by passing sludge streams through 2 No heat exchangers and returning it back to the digesters Hot water, with normal temperature of around 70°C, also is passed through the exchangers

3.1.14.3 Digester Mixing Compressors

Each gas mixing system is dedicated to 1 digester and comprises draw off pipework, duty / standby gas compressors, 12 gas mixing points and associated instrumentation, valves and ancillary plant

3.1.14.4 Waste Gas Burner

Occasionally, the digester may produce more biogas than can be used by the boiler in heating the sludge for digestion Under these circumstances, the surplus gas is destroyed in the waste gas burner

3.1.14.5 Desulphurisation Scrubber

Gas collected will pass through desulphurization scrubber, to remove the H2S in the digester gas

3.1.14.6 Hot water boiler

The digesters are heated indirectly by means of a hot water heat exchanger The heat required is raised using a duty only hot water boiler set

The boiler is fed with gas, from the gas holders, or standby fuel The fuel is kept in a storage tank

Compressors

Digester Building Layout

3.1.15 Gas Holding Tank

The 2 No digesters produce biogas to feed the gas holder as well as boilers and gas mixing compressors in the digester equipment building The 2 No gas holders is a double membrane type with the gas held within the inner membrane Excess gas is directed to a waste gas flare where it is burnt

Gas Holding Tank

Polymer solution is dosed into the feed sludge prior to entering each dewaterer unit

The waste liquors from the dewaterer units flow by gravity to the works liquor pumping station

Sludge Dewatering System

Sludge Dewaterer Polymer Dosing Tank

Dewaterer Feed Pumps

3.1.17 Filtrate Sequential Batch Reactors (FSBR)

Filtrate from the sludge dewatering centrifuges will be the influent to the FSBR The FSBR system is designed to handle up to 1000 m³/Day of filtrate, with two (2) FSBR basins

FSBR consist of aeration, sludge wasting, sludge recirculation and decanting systems

FSBR Aeration System

Blowers Cooling System

FSBR Blowers

Air pipes

FSBR Return Liquor Line

4 Health and Safety

O&M activities will be conducted in accordance with the health and safety plan Future operators will need to generate their own site-specific health and safety plan This plan will need to include, at a minimum, sections that address the following:

 Site location, description, and background

 Emergency contact list

 Proper labeling of process and electrical equipment

 Hot work procedures and permits

o Emergency medical treatment

o Fire and explosion procedures

o Spill control

o Emergency equipment

o Protection of the public

o Emergency contact information

4.1 Mechanical Hazards

These hazards concern risky situation where workers or visitors may be trapped cut, burnt, etc Under normal conditions where the necessary precautions have been taken mechanical hazards can be minimized

- Mechanical hazards arise due to abnormal use or during maintenance

 The places currently under maintenance should be of easy access (draining, greasing, );

 The equipment operating manuals shall be followed;

 Automatic start-up machines shall be turned off and tagged before and during maintenance

 Should an exceptional maintenance operation, which may involve specific risks, be needed, only qualified personnel shall intervene after an operation procedure has been established

4.2 Electrical Hazards

These hazards involve electric shock, burns, electrical injuries, etc to workers or visitors Under normal conditions where the necessary precautions have been taken electrical hazards can be minimized

Electrical hazards arise due to abnormal use or during maintenance

 Always comply with the regulations regarding electrical equipment and installations

 Make sure the installations are in conformity and call for a registered organization to check them each year

 Easily accessible emergency shutdown buttons shall be installed next to the main or hazardous machines (these buttons shall not be used in ON/OFF mode)

 Intervention on electrical equipment shall be carried out by qualified personnel

 Regular material tests shall be scheduled

 All fail-safe controls shall be kept in good working order and in conformity (circuit breaker, fuses, emergency shutdown )

4.3 Falling Hazards

 Ensure that safety equipment is provided and used

 Make sure there is no direct access to the various tanks

 Ensure handrails are in conformity and in good condition

 The personnel shall be equipped with a life jacket and safety harness before tank entry

 Prepare comprehensive intervention procedures, especially for repair work and cleaning work

4.4 Chemical Hazards

Chemicals are used in the Laboratory, SBR, and FSBR

The personnel shall be trained to properly handle chemicals and shall wear:

Gases may come from the sewer network:

 Nitrogen compounds and sulphides Septic effluents generate H2S

 Volatile pollutants, solvents, hydrocarbon gases may be found in the incoming sewage due to accidental or illegal industrial discharge

An increase in CO2 and NH3 concentration may be followed by a shortage of oxygen

Any intervention in a tank, a well or a sewer shall be carried out after gas content has been checked A blower to blow fresh air to the bottom of the structure shall be provided A self-contained breathing mask shall be used for some interventions

An intervention procedure shall be imposed, as follows:

 the person entering the tank must be equipped with a safety harness;

 another person shall remain in the open air ready to help him if necessary;

 Make sure beforehand nothing prevents an unconscious person to be lifted out (eg ladder with safety cage)

4.6 Noise Pollution

Noise pollution has been taken into account since the design stage to ensure that the workers and neibouring residents are not harmed

On the worksite, noise pollution may cause tiredness and may have:

 Occasional health consequences, like tinnitus (permanent and irreversible hissing in the ears)

 And in the long run, loss of hearing and deafness

Interventions in noisy plant rooms shall be carried out with hearing protection equipment

Noise exposure limits

 Hearing Protection if requested

 Medical surveillance if requested

Limited access to the area Individual hearing protection

Appropriate measures must be taken to protect personal such as individual hearing protection

4.7 Odour Pollution

For a wastewater collection and treatment system, odours on worksite are most often the result of odorous materials which are discharged to the system by the public The presence of a gas may be corrosive (for example H2S changed into hydro sulphurous and sulphuric acid) Apart from corroding the structures (concrete and metal parts), odours can also have long-term effects on public health

Pre-treatment is the first source of odour generation The nitrogen compounds and sulphides that are commonly found in the raw water come from bacterial decomposition and volatile pollutants; they are released at the first aeration stage (screening, oil removal,)

Subsequently, there are no real risks of odour pollution, except by accident, during the anaerobic stage Only the sludge withdrawal units may cause odour pollution if the operation is faulty

4.8 Infection Hazards

Sewage is the ideal medium for the growth of most bacterial species which feed on the decomposition of material Waste water contains a large range of pathogenic germs (disease causing agents)

The five groups hereafter listed are the most common:

Tetanus Typhoid Leptospirosis

A, B, hepatitis

Rhinitis, sinusitis Bronchial asthma Chronic mycosis

It is important to ensure that the personnel use proper masks near spray generation areas (tanks with aeration, sludge treatment units)

4.9 Fire Hazard

Good housekeeping is the basis for fire prevention Inspections should be made periodically and correction of fire hazards should be made as soon as possible Consult local fire departments for recommendations Operators should know the fire suppression methods needed to treat the three types of fires

Each operator should have firsthand knowledge of fire extinguisher, its ABC rating point of contact and time of operation

A CO2 fire extinguisher can only be used in an open area where the chance of using up the local Oxygen is

minimal Never grab the horn of the extinguisher to direct the CO2 The gas being expelled will freeze your

hand holding the horn and can cause serious injury There is a handle provided

Regular preventative maintenance of all fire services protection is required

4.10 Basic Health Measures

Ensure that the rules related to personal hygiene and cleanliness and cleaning of rooms and installations are respected and followed by all employees

 Ensure that the personnel are well informed of all the risks and trained accordingly

 Toilets shall be provided with a continuous supply of disinfectant hand soap

 Adequate Information and training shall be provided regularly

 All employees shall be encouraged to wash hands several times per shift

Selected plant personnel must be assigned and authorized to be responsible for the following areas:

 Electrical supplies, maintenance and repairs

 Fire prevention and maintaining fire prevention equipment

 First-aid at work, maintaining first aid supplies on-site

 First aid training for employees

4.11 GENERAL PLANT SAFETY

When working at the plant, observe the following common sense rules

 Keep walkways clear of loose objects such as pails, shovels, loose rope, etc

 Wipe up grease and oil immediately

 Pick up all tools, clean them and return them to their storage area

 When it is necessary to use tools in an empty tank or manhole, etc., lower them in a pail on a rope and remove them in the same way Brooms and shovels can also be transported by rope Do not attempt to climb up and down ladders with your hands full of tools

 Regulations for confined spaces should be followed as applicable

 Do not try to climb up or down a ladder or over a railing when handling a hose under pressure

 Always wear hip wader rubber boots with good treaded soles when washing down the floor of any tank Do not wear rubber boots with worn soles and heels Again, regulations for confined spaces should be followed as applicable

 Always wear the rubber clothing provided when working in a narrow or confined passage where grit

 Maintain signs identifying particularly hazardous areas and the location of first aid supplies

 Do not hang clothes on electrical disconnect handles, light switches or control panel knobs

 Replace all manhole covers and trap doors to wells Close after using If it is necessary to leave them open, protect them with guard-rails

 Use the proper tool when removing or replacing manhole covers Do not attempt to move or close a manhole cover with your hands

 Do not pull up grit-filled pails by hands only when removing from tanks or wet wells

 Use rope with an "A" frame and pulley or some other type of support with a pulley Be sure the support and pulley are fastened firmly to prevent them from toppling over during use

 Always wear a safety belt with a short rope and a safety snap when leaning out through the railings over any tank

 Be very careful during repair work on fuel systems of gasoline engines Close the shutoff valve from the tank and be sure there is adequate ventilation while draining the fuel system

 Check the ventilation of any enclosed or underground areas when gasoline operated pumps are to be used

 Do not refill a gasoline engine when in operation or while still hot Lock out engine before cleaning out pump unit