Excessive COD in wastewater discharge
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For PTA wastewater, an anaerobic + aerobic treatment at both ends process is used. In the first stage, jet aeration is used, while in the second stage, micro-pore aeration is employed. With jet aeration, the COD level of the inlet water is 2000 PPM, and it drops to 260 PPM at the outlet; with micro-pore aeration, the COD level at the outlet is 140 PPM, although it should be below 60 PPM. What adjustments need to be made?
The removal rate for this segment is too high, reaching 87%, which indicates that the biodegradability of this wastewater is fairly good； The low removal rate in the second stage is likely due to excessive decarboxylation in the first stage, resulting in too low a substrate concentration in the second stage, which prevents the bacteria from maintaining normal metabolism.
Thank you. Should I shut down one of the fans in section 1 to increase the COD level of the water output from that section?
Please provide information on your operation parameters, such as SV30, BOD, MLSS, retention time, pH, etc. Operational data is necessary for accurate analysis and assessment. In such cases, it is necessary to keep the dissolved oxygen level in the secondary stage from being too high; 0.5–1 is sufficient. Some of the raw water should be directed to the secondary stage, or an additional carbon source should be added to ensure that there is enough carbon source in that stage (in other words, to maintain the organic load within normal levels) ； Additionally, the levels of nitrogen and phosphorus should not be too low either; generally, levels around those specified in the emission standards are sufficient.
In some plants, the quality of the water from the secondary treatment stage is worse than that from the primary treatment stage, which is largely due to insufficient nutrients and excessive aeration
Let’s increase the sludge concentration in the micro-pore aeration tank; it seems that additional facilities will be needed to keep the concentration below 60
The sludge concentration in the second stage is relatively low, with an MLSS of only 1800; it is likely that the load is too low, and at the same time the aeration volume is too high. Aiming to reduce aeration, efforts are being made to do so continuously these days.
Reduce the dissolved oxygen level resulting from jet aeration; the COD level in the water discharged from jet aeration has risen to 320 PPM over the past two days. However, the COD due to micro-pore aeration did not decrease; instead, it increased by the same proportion and reached 200PPM. What’s going on?
Should we try using some fungicide?
With the biochemical removal rate already being high enough, it is necessary to consider physical-chemical methods, such as various oxidation and flocculation processes.