Sewage Treatment Plant ELIL ABODE

STP Figure A3A1 A2 S1 S2 SF F1 F2 CF

OPERATION 1.Input tank with bar screen :- All the flush toilet sewage, bathroom waste water, kitchen waste water enters in this tank. There is a mesh which filters out non-sewage material if any. 2.Aeration tank :- Input is from tank no 1. The chemical powder which is added in tank 1 comes into this tank. The bacteria in the chemical act upon the sewage and decompose it. There are 3 air blowers in this tank one at the bottom and two floating (at some height) which pump air into the system. The oxygen is necessary for the bacteria to survive, reproduce and decompose the sewage. 3.Sludge tank :- Input is from aeration tank through a pipe due to gravity. This pipe is at little lower level then the pipe which connects tank 1 and tank 2. So as the sewage builds up in tank 2, it flows naturally in this tank. Here sludge is left to settle down and water gets separated and floats.

OPERATION Contd... 4.Pre Filtration tank :- Input is from tank 3. Here again due to natural flow, water comes through a pipe which is at little lower level than the pipe connecting tank 2 and tank 3. This is first stage of filtration. 5.STP room :- This has 2 big filters and all the electrical connection required to run motors and air blowers. One filter is carbonized filter and other is sand filter. This is a serial process. Water from tank 4 first enters into carbonized filter and gets treated and then it goes to sand filter, gets treated and finally it goes out in a small tank where UGD pipe is connected which takes it to the main sewage outside. 6.Digester tank :- The waste remaining in carbonized and sand filters after treatment of water is sent to this tank with the help of separate pipes from each filter which keeps getting accumulated and has to be cleaned once in a year.

OPERATION Contd... Few extra points: -Sludge settled in tank 3 is sent out to tank 1 at regular intervals (2/3 times in a day) to get decomposed in the aeration tank again. This recirculation is necessary to get more effective treatment of sewage. -Tank 3 (sludge) and tank 4 (filter) have 2 motors each. At a time only one motor is operational in each tank and other is in standby mode. But to make sure both the motors are in operational condition they are run on alternate days that’s why STP room has 2 filter pipes (F1 and F2) and 2 sludge pipes (S1 and S2) with manual knobs on each to run them one by one. -There is an electrical panel board in STP room which controls all the motors and aerators. It has manual as well as automatic mode.

ELECTRICAL PANEL BOARD If we stand facing the panel, then above is the sequence of relays controlling different motors. F1/F2 :- Filter tank motors S1/S2 :- Sludge tank motors SPARE :- As the name suggests, can be used if anyone is not working A1/A2/A3 :- Aerators F2F1S1S2A3 SPA RE A1A2MAIN INPUT

CURRENT CONDITION Current condition of STP -5 relays and 5 contactors in electrical panel board are not working which will take around 9000/- to get fixed. -Sludge tank doesn’t have any motors. There are 2 motors put in filter tank but only one is functional. 2 motors are kept in STP room which seem to be OK at the first inspection. Due to electrical panel board problems, aerators could not be checked. If any of these motors are found to be non-functional, the repair can happen only in Coimbatore and it will cost 6500/- per motor. -The carbonized and sand filters are not used right now. It has to be checked if they are fine or the media inside them has to be replenished which might cost around 20000/-. -Bar screen in tank 1 hasn’t been cleaned for years. We need to check it and see if it needs a replacement which will cost 3000/-.

CURRENT CONDITION Contd… Current condition of STP -The chemical powder is not being put right now. We put some liquid chemical which is not perfect for the job. -As the carbonized and sand filters are not getting used, water is being pumped out directly from filter tank (tank 4) to the small open tank which connects to UGD and as it is fully untreated water, it gives really foul smell. And it is highly unhygienic and unhealthy. -With the sewage, lot of waste material like sanitary napkins etc are also being flushed out from flats to STP tank which deteriorates STP’s performance.

Immediate steps Steps to be taken immediately to revamp STP -Electrical panel board has to be made functional asap. -Bar screen has to be cleaned and changed if needed. -All the sludge and filter tank motors have to be put back in the tanks and connected. -One operator needs to be kept for the whole day to maintain STP at least for next few months till STP starts functioning properly and all the problems are resolved.