Construction, Operation and Maintenance Aspect

CONSTRUCTION, OPERATION AND MAINTENANCE ASPECT

Maintenance Scheduling

• Maintenance of each equipment is done as the recommendations of manufacturer.

• A History card is maintained for each equipment so that record is maintained for equipment performance and maintenance.

• Good housekeeping is an important aspect of plant operation.

Pumping Machinery

• To run the machinery in a way so as to have free fall from invert of sewer.

• Mostly 2 or 3 pump sets are out of order.

• Minimum one pump be operated during night hours so that sewers are empty in Hiw z morning.

• Guide Wire/ Guide Rail should be in good condition.

Screening Chamber & Wet Well

• Regular Cleaning

• Disposal of Screenings

• Washing of Bar Screens

• Washing sludge layer from walls using waterjet

• Desilting of wet well once a year.

Cleaning Chamber & Fine Screens

• Should be sccured minimum once in a week.

• Fine Screens should be kept clean of all obstructions. If the screen are of mat type, its operation should be adjusted such that a mat is always on the screen.

Grit Channel

•  (1W+18) grit channels for peak flow.

• Should be used one at a time, alternatively everyday.

• Should be cleaned everyday.

• Proper & efficient removal of silt in grit channel will improve the functioning of treatment.

Proportional Weir

• It is provided to maintain uniform flow on upstream and downstream of gritchannel.

• Must be calibrated so as to show the quantity offlow.

• Flow be recorded every hour. In SBR Plants the flow recording graphs are recorded in SCADA

Distribution Channel

• Must be cleaned every day.

Moving Bed Biofilm Reactor (MBBR)

The STP is said to be running successfully, if:-

• The biofilm layer shall accumulate on the biomedia.

• The flocs should generate in clarifier.

• The smell of sludge should not be foul.

• When starting the plant initially, the air blowers should be operated for passing the air through diffusers and run continuously,otherwise the desired parameters will not be achieved.

• Fill both aeration tanks to the normal operating sewage depth, thus allowing the aeration equipment to operate at maximum efficiency.

• Using all of the aeration tanks will provide the longest possible aeration time.

• The effluent end of the aeration tank should have a dissolved oxygen level of at least 1.0 mg/L. DO in the aeration tank should be checked every two hours. Generally the DO is approx. above 4 in aerated sewage.

• The COD reduction in treated sewage Vs. raw sewage cannot be less than BOD reduction.

How to check DO in Aeration Tank

The presence of DO in aeration tank requires the elaborate procedure of using a meter operated electronically and keeping the probes well cleaned at all times. This is not always possible. Moreover, typical plant control requires an answer to the question of whether residual DO is present or absent in the secondary clarifier overflow. This can be easily carried out in the field as follows:

1. Take a 10 ml well washed test tube.

2. Hold it gently against the weir overflow sideways.

3. Allow the sewage to fill the tube and overflow for a few minutes.

4. Gently take the tube and pour out about 2 ml.

5. Add few drops of manganous sulphate solution.

6. Add a few drops of potassium iodide solution.

7. Close the top with the thumb and invert a few times.

8. Allow to stand for a few minutes.

9. If there is a yellow precipitate, DO is present.

10. If there is a white precipitate, there is no DO.

• With help of electronic instrument.

• Online sensors are required to be provided.

Reactors/SBR

• 2 in nos. (parallel & in series).

• The problem of foam can be solved using water jet.

• Reactors should be desludged every day to maintain proper MLSS.

• The walls, walkway and the railing to be washed daily using waterjet.