What is Standard Operating Procedures (SOP) for maintenance of STP Plants?
The Standard operating procedures that must keep in mind for sewage treatment plants' operation and maintenance. What is Standard Operating Procedures (SOP) for maintenance of STP PLANTS?
This article will ascertain the different parts installed in a sewage treatment plant and what considerations should be considered for their operations and maintenance, respectively.
Bar Screen Chamber
The primary function of a bar screen chamber is to prevent solid particles such as plastic cups, paper dishes, bags, etc. into the STP. It is done to avoid clogging and damaging STP pumps. This screening process is achieved by placing a screen made of vertical bars on the sewage low. If left unchecked, it can cause considerable damage, such as sewage backing in the pipelines and chambers. Following are SOP’s listed below:
- 1. Bar screen should be checked and cleaned at frequent intervals.
- 2. Corrosion of the screen can be avoided if there is no formation of significant gaps. Hence, it should be checked from time to time.
- 3. Corroded and unserviceable bar screens should be replaced immediately.
- 4. It must keep in mind and ensured that no solids are Overflow or escape from the screen.
- 5. Proper disposal should be made of the screened materials as per the sewage and sewage treatment provisions manual.
The primary function of a grit trap is to separate the solids and fats from the sewage wastewater and disposed of them properly along with the other bio-degradable waste. This separation of solids and grease at the outset ensures that contact time between solids and wastewater is kept minimum. The wastewater doesn't absorb organic pollutants such as starch and carbohydrates. The solids settle at the bottom and must be cleaned frequently. Otherwise, it would fail to serve its primary purpose. Following are SOP’s listed below:
- 1. Ensure that the solids, oil, and grease do not get washed out of the trap.
- 2. The trap must be cleaned and checked at frequent intervals.
- 3. Settled solids, grease, and other screened materials should be treated as per the sewage and sewage treatment provisions manual.
- 4. The trap should be redesigned if, even after The excellent cleaning, let's escape the solids and grease.
The primary function of an aeration tank is to maintain a high population of microbes and microorganisms. It is one of the essential functions and is conducted along with a settling tank or a clarifier. The mixture so formed in this process is known as mixed liquor Suspended Solids (MLSS). MLSS is then passed on to the clarifier, where microbes are made to settle at the bottom. The settled microbes are then recycled to the tank, where they are retained for a longer duration. Following are SOP’s listed below:
- 1. The aeration tank should maintain the correct design level of MLSS. The biomass level should also keep, and should neither be excessive nor be short. It should be balanced.
- 2. The equipment of aeration should be operating continuously.
- 3. In case of stubborn encrustation, the mild acid solution should be scrubbed off.
- 4. Membranes should be neat and clean. The dead zones can indicate the need for cleaning membranes on the sewage surface.
- 5. DO concentrations of around two mg/l be maintained throughout the aeration tank.
Secondary Clarifier/Settling tank
The primary function of a secondary clarifier or a settling tank is to allow the settling of solids in the mixed liquor that comes out of the aeration tank. It also thickens the settled biomass so that it can produce a thick underflow. Besides this, it aids in making clear supernatural water in the Overflow from the clarifier. It is important to note that a clarifier tank is only a passive device. The actions that occur are only due to gravity. Following are SOP’s listed below:
- 1. No scum formation should take place over the surface of a tank.
- 2. The bridge of the tank should keep running.
- 3. Launder must be clean.
- 4. Sludge should be removed from time to time.
- 5. The treated water should remain consistent over the length of the launder. It will ensure good aeration.
Aeration tank, settling tank, and sludge recirculation together constitute an activated sludge biological treatment system. It must be designed to have the desired level of high treatment given in the sewage treatment process. Since the STP is required to maintain high levels of microbes, this is done with the help of sludge recirculation from the settling tank. Following are SOP’s listed below:
- 1. Safety guards should be kept in the proper position.
- 2. The bypass valve should not tamper. The flow rate should be maintained at a designed level.
- 3. Condition of bearings, oil, seals, and mechanical seal should be looked at and replaced whenever necessary.
- 4. Vibrations should be checked for and must tighten anchor bolts and fasteners.
- 5. The main and standby pump should be switch over after every 4 hours approximately.
- 6. Its damaged parts must are replaced immediately.
Pressure Sand Filters
It is used as a tertiary treatment to trace the amounts of solids that could escape the clarifier. It can handle up to 50 mg/l if solids in an economical way. The unit is filled with sand and gravel, usually termed as graded media. The water is filtered with PSF and then passed on to the next stage in an STP chain, i.e., activated carbon filter. Following are SOP’s listed below:
- 1. The filter should be backwashed when the pressure drop exceeds 0.5 kg/cm2. It is recommended that backwash is done once in a shift, irrespective of the pressure of loss.
- 2. Five to ten minutes of backwash is preferred since it will filter the entire accumulated tank.
- 3. The operation of a pressure sand filter requires that there should be extended run filtration that is followed by a short backwash sequence.
Activated Carbon filter
Just like a pressure sand filter, an activated carbon filter is also a tertiary unit. The water received is already filtered by the pressure sand filter. It improves the multiple quality parameters of the water, such as BOD, COD, clarity (turbidity), color, and odor. Following are SOP’s listed below:
- 1. It also requires frequent backwash similar to that of a pressure sand filter. But it should be comparably in lesser frequency to dislodge any solid particles trapped by simple filtration action.
- 2. The fresh carbon filter should be installed immediately; otherwise, it will lead to poor water quality.
Disinfection of treated water
The water treated is then disinfected so that the chemicals and other microorganisms present in the water get destroyed. It is necessary because it can lead to various health hazards and invite water-borne diseases to attack our immune system if not treated. One of the best methods to disinfect water is chlorination. The other disinfectants such as Sodium hypochlorite, chlorine gas, UV treatment can also be considered for disinfection. Following are SOP’s listed below:
- 1. The chlorine solution should be injected into an effluent through either a diffuser or flash mixer for the best results.
- 2. The chlorine system should be applied continuously.
- 3. The chlorine detention time should be a minimum of 60 minutes.
- 4. The proper treatment of chlorine gas must be done because it would sometimes come out un-dissolved. It will ultimately lead to a reduction in the efficiency of disinfectants and an increase in costs.
Excessive Sludge Handling
The biological treatment of wastewater leads to excessive biological solids due to the system's growth and replication of microorganisms and bacteria. The excess mass needs to be disposed of properly. This occurs in five steps, i.e., sludge removal, storage, conditioning, dewatering, and disposal. Sludge recirculation removes the sludge from the system efficiently. Sludge is moved through all these five steps, and then it is disposed of properly. Following are SOP’s listed below:
- 1. Filter cloths should be pre-cleaned with a hypo solution. It will help in prolonging the life of a fabric.
- 2. If the filtration process becomes slow, it indicates that the filter cloth requires replacement with a fresh set.
- 3. The rubber stator of the screw pump should be appropriately maintained, and efforts should be taken not to damage it.
- 4. The pumps must be located in such a way that the positive suction is enabled.
- 5. Sludge drying beds
- 6. The sludge drying beds must be covered with a lime layer to avoid a bad smell.
- 7. The sludge drying should be enhanced by flipping and scrapping at regular intervals.
- 8. The dried sludge should be continuously removed from the sludge beds and stored in bags.
- 9. Proper collection of sludge should be maintained at the plant.
These were the SOP's that were required for the maintenance and operation of STP. We hope that you will take care of these SOPs in maintaining your sewage treatment plant.
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