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K.A.J.W Siriwardhana.

Introduction.

“Operation and maintenance refers to all of theactivities needed to run a water supply andsanitation scheme, except for the constructionof new facilities. The overall aim of operationand maintenance is to ensure efficiency,effectiveness and sustainability of water supplyand sanitation facilities”

-(CASTRO 2009)

• Operation & Maintenance (O&M) service means that we care about your assets.

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With our experienced and highly qualified personnel we will provide the following services:

• Operation (24/7)

• Preventive Maintenance

• Corrective Maintenance

• Condition Monitoring

• Remote Monitoring by Expert Center

• Provision of Spare Parts and Consumables

• Repair and Refurbishment of major components

• Execution of scheduled Outages

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Operation and maintenance of a water treatment plant.

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Screeners:• In the case of hand raked screens, the screens should be raked at least hourly.• Screenings should be allowed to drain for an hour, until the screen is raked

again.• Surfaces on which screenings have been deposited, should be hosed down on a

daily basis, in such a way that wash water flows back into the wastewaterstream.

• There is often more than one grit channel or grit removal hopper.• Grit channels should be taken out of operation at least once a day, drained and

the grit deposited onto drainage platforms• The total flow should be read daily at the same time and recorded.

Screeners(cont.):

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Coagulation & flocculation:• There usually are two parallel systems of coagulation/flocculation units in a

treatment plant to facilitate removing one half of the basins from service for maintenance.

The best flocculation usually is achieved by more than one unit in a series.

Each unit is separated by baffles to prevent short circuiting. Also, all inlets and outlets are baffled to prevent short circuiting.

• The flocculators usually are driven by variable speed drive units. With multipleunits, it is desirable to reduce the speed of the flocculators in each succeedingunit to prevent breaking up the large floc particles which have formed.

• The flocculators should have a detention time of 30 minutes.

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• In the event the flocculation units appear to be ineffective, a carefulanalysis of the process should be done using jar tests, varying both thedoses of chemicals and the speed of the flocculators to determine if animproved process could be developed.

• The maintenance of the flocculation drive units usually is lubrication ofthe motor and drive units according to the manufacturer'srecommendations.

• Horizontal paddles usually have submerged bearings, drive chains, orpacking which requires additional checking and maintenance.

• The flocculation basins should be drained approximately every six monthsto check the condition of the paddles or blades, to remove anyaccumulation of settled material, and to check on the condition of thebasin's structure.

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Coagulation & flocculation (cont.):

• Sedimentation is the slow, quiet settling of the floc and suspendedmatter from the water by gravity. The sedimentation basins can berectangular or circular in shape.

• There should be at least duplicate units to facilitate cleaning.

• The basins should have a detention time of four (4) hours.

• The inlet devices should be designed to distribute the water foruniform velocities and care should be taken to prevent short circuitingof flows.

• There should be surface skimming to collect floating debris, such asleaves, scum, etc.

• When the basins are drained for cleaning, the condition of the basinsand the sludge collection equipment should be checked carefully.

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Sedimentation:

Sedimentation(Cont.):

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Filtration:• The filtration process is the passing of the water through a bed of fine material, such

as sand, coal, or other fine granular material. The filter media can be uniform insizing, but higher and more effective filter rates are attained by use of mixed media.

• As a coating builds and penetrates into the filter bed, the head loss across the filterbecomes greater until the flow rate is greatly reduced. At this time the filter must bebackwashed to cleanse the media of the floc and particulate matter.

The filter control valves should be checked routinely for proper operation andany leakage.

The filter media should be examined annually to evaluate its overall condition. Isthe media uniformly graded and distributed? Is there the proper depth of eachgradation of media? Expose the underdrain system to check if the holes ornozzles are clogged.

The backwash and surface wash pumps should be checked and lubricatedaccording to the manufacturer's recommendations.

The surface wash equipment, including nozzles, should be checked periodicallyfor free operation and proper position over the media.

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Disinfection:• Water can be disinfected by heat, radiation, or chemical treatment; however,

the only widely accepted method is chemical treatment.

• Chlorination usually is accomplished by either gas chlorinators, hypo-chlorinators or chlorine dioxide generators.

On a daily basis chlorinators should be inspected for proper operationand leaks. The items to be checked should include injector watersupply pressure, injector vacuum, chlorine supply pressure feed rateon roto-meter tube.

The chlorine residual should be checked and recorded.

On a weekly basis check chlorinator feed rates through the full rangeof its capacity, clean any filters, and check operation of all valves.

On a monthly basis, exercise all chlorine valves, inspect ventilation,heating, and lighting equipment for proper operation.

Check the chlorinator vent line for obstructions such as insect nests,inspect the vacuum system for leaks, and perform othermaintenance.

Inspect all safety equipment for proper operation including chlorinealarm system and the self-contained breathing apparatus or gasmasks. 1

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Disinfection(Cont.) :

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Disinfection(Cont.) :

• Some abnormal operating conditions which could occur are:

Chlorine leak - A chlorine leak is usually detectable by your sense of smell assoon as you arrive at the chlorination location.

Low gas pressure - If the chlorine gas pressure drops, it usually is the resultof the chlorine container being empty, clogged filters, or closed valves. Tocorrect, replace the container, clean the filters, and check the valves.

Injector vacuum too low - If the injector vacuum drops too low, thechlorinator should automatically shut off. The cause of the vacuum beinglow is a leak in the vacuum hoses, low water pressure, or clogged ejector.

If there is a vacuum leak, repair the leak. If there is low water pressure,check the source, pump operation, or line strainers. If the ejector isclogged, remove and clean it.

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Disinfection(Cont.) :

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Advantages. Disadvantages.

•O&M activities ensure that the project is sustainable in a long-term

•O&M allow for the correct provision of services and benefit of end-users

•O&M prevent the systems to collapse creating environmental and health hazards

•Community can be involved in O&M

• O&M activities cost time and money, and therefore a provision for financing O&M has to be planned before the project starts

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Reference

1. Beyond, A., Control, E. S., & Knowledge, O. (n.d.). Chapter 3 O & M Management, 1–15.

2. Plan, M., & East, F. T. (2000). APPENDIX B OPERATIONS & MAINTENANCE PLAN.

3. Requirements, B. (n.d.). OPERATION AND MAINTENANCE MANUAL FOR WASTE WATER TREATMENT WORKS DPW ’ s BASIC REQUIREMENTS.

4. Swartz, C., & Utilisation, W. (n.d.). OPERATION OF WASTEWATER TREATMENT PLANTS.

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THANK YOU

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1. Why do we need to operate and maintain a water treatment plan?

2. What are two main maintenance methods?

3. What should be checked in the water treatment plant in daily routines?

4. How do the durability of assets are ensured with maintenance purposes?

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