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Wastewater Commissioning Guides-Part 4
- Mar 14, 2018 -

Wastewater Commissioning Guides-Part 4

9. The average data of water, effluent, and biochemical pools of the plant in the past week are as follows:

Influent: BOD: 253; COD: 810; PH: 7.9; SS: 286; Chromaticity: 32 times; Ammonia: 28; Total Nitrogen: 64; Total Phosphorus: 6.0;

Effluent: BOD: 4.8; COD: 74; PH: 8.1; SS: 12; color: 8 times; ammonia: 7.6; total nitrogen: 22.8; total phosphorus: 1.02;

Biochemical pool: MLSS: 4200; MLVSS: 2340; SV%: 47.2; Sludge index: 118.9; Sludge age is 35 days.

The modified activated sludge process is used. The current influent water is only about 25,000 tons/day (design is 50,000 tons), 80% is industrial wastewater, and there is a small amount of landfill leachate with high concentration. The process is an aerated grit chamber - post-biochemical pond - post-secondary settling pond, without contact and hydrolysis ponds. The biochemical pool is supplied by a blower, and a deep-water rotary disc aeration results in a dissolved oxygen of less than 1 mg/L in continuous water intake. After the water is stopped, the dissolved oxygen slowly rises to about 4-5 mg/L. The serious water ingression and structural defects have led to a high load on the biochemical tanks, and the sludge thickening tank is very small (180 cubic meters). A considerable part of the excess sludge is returned to the pump room.

Now the problems encountered are: (1) The secondary sedimentation tank often finds activated sludge suspended particles after entering the water. Is it due to insufficient time for precipitation or difficult precipitation?

(2) The three secondary sedimentation tanks were found to have aggregated red worms (water fleas). The leeches seem to be a good treatment of water quality. Is it because the high sludge concentration leads to a large number of breeding?

(3) The secondary sedimentation tank is sometimes found to have a thin layer of floating sludge. Is the sedimentation performance of the sludge very poor and the aeration of the biochemical pool is insufficient? Or is the sludge backflow not timely?

(4) What is the method of overcoming moss or algae breeding in the second sedimentation tank?

(5) I think that the sludge has been severely deteriorated. To reduce the MLSS control to between 3000-3500 or less, increase the excess sludge discharge and reduce the sludge age, will the impact resistance of biochemical pools decline? Water quality will not rise?

Answer: The sludge is somewhat aged, but it is not very serious. The sludge age has reached 35 days. Based on this calculation, the sludge load is less than 0.03. Controlling 2/3 of the current sludge concentration is sufficient, and the sludge concentration should be gradually reduced. The leeches have no effect on the effluent. Do not take leeches when analyzing samples. Also pay attention to the sediment pool mud control, and the moss and algae on the triangular plate of the second settling tank can only be manually removed.