The risk and the transition time: two aeration tanks in parallel adjust to anoxic tank and aeration tank in series

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Dear all,

The process deal with high chloride (about 10,000 ppm) wastewater is two aeration tanks in parallel now, we plan to adjust the aeration tanks to anoxic tank and aeration tank in series, while we need to keep the effluent COD <50 ppm and ammonia nitrogen <5 ppm for the continuous water monitoring system . Could someone kindly tell us the risk and the time of transition, thanks all.

The hydraulic retention time of two aeration tanks in parallel is about 12 hrs , the pH about 8, the DO 3~4 ppm, the MLSS 4,000 ppm, the temperature of aeration tanks about 33~36°C.the influent COD is about 1,000 ppm, the Kjeldahl nitrogen about 50 ppm; the effluent COD is about 40~50 ppm, the Kjeldahl nitrogen about 2~5 ppm.

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4 Answers

  1. Here is the reply from Chat GPR: how do you think he/she/it did? 

    Transitioning from two aeration tanks in parallel to an anoxic tank and an aeration tank in series to treat wastewater with high chloride concentrations of about 10,000 ppm may present some risks and challenges. The new configuration may require changes to the plant's operation and maintenance practices, and may result in temporary disruptions to the treatment process.

    One of the main risks associated with this transition is the potential for increased energy consumption. The new configuration may require additional energy to maintain the anoxic conditions in the anoxic tank, and to operate the additional pumps and equipment required for the new configuration.

    Another risk is the potential for decreased treatment efficiency during the transition period. It may take some time for the plant operators to optimize the new configuration, which could result in temporary disruptions to the treatment process and a decrease in the quality of the effluent.

    To maintain the required effluent COD <50 ppm and ammonia nitrogen <5 ppm for the continuous water monitoring system, the new configuration will need to be carefully optimized and monitored. The anoxic and aeration tanks will need to be operated with the appropriate hydraulic retention times and DO levels to ensure efficient removal of COD and ammonia nitrogen.

    The transition time from two aeration tanks in parallel to an anoxic tank and an aeration tank in series can vary depending on the complexity of the new configuration and the experience and expertise of the plant operators. In some cases, the transition may be completed relatively quickly, while in other cases it may take several weeks or months to fully optimize the new configuration.

    It is recommended to carefully plan and monitor the transition process to minimize disruptions to the treatment process and ensure a smooth transition. Additionally, plant operators should closely monitor the effluent quality during the transition period to ensure that the required COD and ammonia nitrogen levels are being met.

  2. pH, Tem and dissolved oxygen are three vital parameters in aeration tanks – DO need be maintained at 1-3 mg/L for an effective treatment as the low DO level would harm microbial mass which is difficult to reestablish.  While operation of aeration pumps is costly, allowing more than 3 mg/L looks a wasteful use of resource.  Similarly >450 C would check nitrification process and therefore the ideal is between 28 & 320C.  Similar impact at low temperatures than 28.  pH ideal is 6.5 -8.5 to avoid stress on microbial community and entertain optimal biological activity.

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  3. Hello On a research of waste water analysis, of two years, for a habitat preserving the biological characteristics of the waste water, without chemical product, I realized that the oxygen was gradually degrading the Ph. Indeed urea in the presence of oxygen produces ammonia which interferes with the other components of urine. The aeration of the waste water only temporarily halts the degradation by the process of anaerobic digestion (putrefaction) of the suspended matter.

     

  4. The major risk is the Anoxic tank becoming part anaerobic due to insufficient nitrates at higher HRT & affecting the overall denitration process. You will also need to increase the recycle ratio from aerobic to anoxic to cope with this.


    Other obvious things are the growth of filamentous bacteria, SRBs which ultimately affect your settling properties and also the risk of denitration happening in secondary clarifiers are some things that will affect your settling properties & effluent discharge standards.