High ammonia nitrogen in the A/O tank, abnormal effluent quality
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Our company is a petrochemical enterprise, and its wastewater treatment process consists of: adjustment – oil separation – flotation – A/O process – secondary sedimentation – discharge (the facilities used are relatively small). Recently, the discharged wastewater has high levels of ammonia nitrogen and COD, as well as turbid water. Oil was first discharged due to an accident in the production facility, resulting in a large amount of oil entering the A/O tank. An operator error caused a large amount of wastewater from Tank A to flow into Tank O, turning the surface of Tank O black. A few days ago, the sulfide level in the water exceeded 171, which had an impact on the sludge as well. The incoming water is yellow; sulfide levels are normal, while ammonia nitrogen at 300 is significantly above the allowable standards. This results in yellowish and turbid effluent, as well as oil emulsification, with levels of ammonia nitrogen, COD, and SS all exceeding the specified limits. Pool O has insufficient aeration, and the water entering Pool A contains fibrous crystalline substances (resembling glass wool) that dissolve in water when heated. After baking, similar to the case with discharged wastewater, white particle precipitates remain at the bottom of the water. There is sticky foam on the surface of Pool O, and there is a large amount of sticky, oily sludge in the secondary sedimentation tank. The inlet and outlet parameters for today are as follows: COD: Outlet 184.09, Pool O 305.48, Pool A 371.87; Ammonia nitrogen: Outlet 78.55, Pool O 105.67; Inlet 27.37 (values vary due to intermittent discharge of acidic water with high ammonia nitrogen levels); Phosphates: Pool O 3.44; DO 1.81; Sulfides: Inlet 10.66, Discharge 0.17; Petroleum substances: Inflow 36.47, no detectable emulsified substances in the discharge; pH: 8.15. Could experts help me answer the following questions: 1. What are the causes of sludge buildup, and what are the solutions? 2. What are the solutions for high ammonia nitrogen levels? 3. Solutions to the problem of excessive COD in the effluent (this issue should be resolved once the first two problems are addressed). 4. What could the fibrous material and white particles be? What caused it? (Products generated during COD measurement) 5. Will injecting a large amount of fresh water at the front end of tank A to replace the polluted water in the A/O tank be effective? Are there any downsides?
Reply to 1# king5921: After some consideration, here are some suggestions for the original poster. 1. Control the quality of the water entering the system; this is probably the most important factor. 2. If there is excess activated sludge available, add it to the aerobic tank as soon as possible, and increase the sludge discharge rate to boost the activity of the sludge (ammonia nitrogen can only be removed once the sludge is in proper condition and has an adequate age). 3. Maintain an appropriate nutrient ratio. 4. The DO level should ideally be above 2
Reply to 2# afei666254: The preliminary estimate is that oil was discharged due to an accident in the production facility, resulting in a large amount of oil entering the A/O tank； Excessive sulfides in the influent have an impact on the sludge, leading to sludge poisoning (the symptoms include sludge mixing throughout the secondary sedimentation tank, with significant increases in COD, oil, ammonia nitrogen, and suspended solids levels in the effluent). To address the aforementioned issues, the following targeted measures have been taken to improve the situation: (1) sludge removal from the aeration tanks, (2) reducing the pollution load of the incoming water, and (3) increasing the number of operating cycles for the secondary sedimentation tanks. The problem cannot be solved in a short time; however, over the long term it should be possible to restore its activity, and the harm won’t be severe. But what I want is a proper solution in the short term. . . .