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    Home > Chemicals Industry > Chemical Technology > New technologies and new processes for biological nitrogen and phosphorus removal from sewage (1)

    New technologies and new processes for biological nitrogen and phosphorus removal from sewage (1)

    • Last Update: 2021-06-18
    • Source: Internet
    • Author: User
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    Since the 1980s, biological removal of ammonia and phosphorus technology has made significant developments
    With the strengthening of the awareness of the importance of the prevention and control of eutrophication of water bodies, many countries have increased or improved the requirements for nitrogen and phosphorus in the discharge standards.
    For this reason, a large number of biological nitrogen and phosphorus removal sewage plants have been constructed and used, and according to Different water quality conditions and treatment requirements have proposed many biological denitrification and phosphorus removal processes and improved processes

    Phoredox process (P modified Barton process), the UCT process, the VIP process, Tupper card, the CASS process or the like

    In general, biological removal of ammonia and phosphorus is mainly developed in the direction of improving efficiency, shortening hydraulic retention time, combining suspension and adhesion, and miniaturization of equipment


    Some recent studies have proved that there are Denitrifying Phosphorus Re-moving Bacteria (DPB) in activated sludge.
    They can also take up phosphorus, that is, NO
    3 while denitrifying and denitrifying under anoxic conditions.
    - -N no longer seen as an inhibitory factor phosphorus removal process, but rather denitrifying reaction of phosphorus as the final electron acceptor, offers a new approach to biological phosphorus removal
    Denitrifying phosphorus removal is to replace the traditional anaerobic and aerobic environment with anaerobic and hypoxic alternate environment, domesticating and cultivating a kind of denitrifying phosphorus accumulating bacteria (DPB) with nitrate as the final electron acceptor.
    Metabolism to complete the process of excess phosphorus absorption and denitrification at the same time, so as to achieve the dual purpose of nitrogen and phosphorus removal

    The advantage of denitrification and phosphorus removal technology is to save carbon source and energy

    The limited carbon source in conventional biological denitrification and phosphorus removal processes is only sufficient for denitrifying bacteria or phosphorus removal bacteria, while denitrification and dephosphorization enables the available limited carbon sources to meet the needs of both denitrification and biological phosphorus removal

    From the viewpoint of microbial ecology, only nitrification requires an aerobic environment, and the denitrification and phosphorus removal process does not require aeration

    The existence and proliferation of DPB does not mean that the anaerobic section is omitted in the biological nitrogen and phosphorus removal process, because the omission of the anaerobic section results in the transfer of bacterial activity from phosphorus removal and denitrification to ordinary denitrification

    Applying denitrification and phosphorus removal technology to treat urban sewage can not only save aeration, but also reduce the amount of remaining sludge, so that investment and operating costs can be reduced

    Denitrification and dephosphorization and denitrification reactors are divided into single sludge and double sludge systems

    At present, the typical dual sludge systems include A
    2 N process, Dephanox process and HITNP process
    The representative of the single sludge system is the UCT process, and the BCFS process is a modified UCT process

    In addition, new ways to achieve denitrification and phosphorus removal include AOA-SBR method, granular sludge method, internal circulation air-lift sequencing batch biofilm method (internal circulation air-lift SBBR) and so on


    1 BCFS nitrogen and phosphorus removal process

    This process is a modified UCT process.
    The UCT process design principle is based on the engineering enhancement of the environmental conditions required by the phosphorous accumulating bacteria.
    The development of BCFS is to create DPB enrichment conditions from a process perspective

    According to the denitrification and phosphorus removal mechanism, in a single activated sludge system, a pre-denitrification section (pre-anoxic section) should be set up, and the nitrate-rich activated sludge from the end of the aerobic section is returned to the pre-denitrification.

    The anaerobic section is connected with the pre-anoxic section to receive influent and sludge flow from the pre-anoxic section with little nitrate content (similar to the UCT process).
    The BCFS process consists of 5 functionally independent reactors (anaerobic Pool, selection pool or contact pool, anoxic pool, mixing pool, aerobic pool) and 3 circulation systems (as shown in Figure 6-4)

    Cycle A is to provide phosphorus release conditions, that is,
    nitrate <0.

    Because the return sludge is directly introduced into the selection tank, it is very important to set the internal circulation B from the aerobic tank to the anoxic tank.
    It plays the role of assisting the return sludge to replenish nitrate nitrogen to the anoxic tank

    The setting of circulation C is to establish a circulation between the aerobic tank and the mixing tank to increase the chance of nitrification or simultaneous nitrification and denitrification, and to create conditions for obtaining good effluent nitrogen concentration


    Figure 6-4 BCFS process flow

    In this process, 50% of the phosphorus is removed by DPB.
    The living environment of bacteria in each reactor is optimized by controlling the 3 cycles between the reactors, and the anoxic denitrification and dephosphorization effect of DPB is fully utilized to realize the phosphorus removal.
    Complete removal and optimal removal of nitrogen

    Make full use of the affinity of phosphate bacteria for phosphate, organically combine biological phosphorus uptake with phosphorus-rich supernatant (from anaerobic release) offline chemical precipitation, so that the system can obtain good effluent water quality


    From the process flow point of view, the innovations of the BCFS process compared to the UCT process are as follows

    (1) The BCFS process adds 2 reaction tanks, that is, a contact tank is added between the anaerobic and anoxic tanks of the UCT process, and an anoxic/aerobic mixed tank is added between the anoxic tank and the aerobic tank
    This design can not only inhibit the reproduction of filamentous bacteria, but also form a low-oxygen environment to obtain simultaneous nitrification and denitrification, thereby ensuring a lower total nitrogen concentration in the effluent


    (2) The BCFS process adds on-line separation and off-line precipitation chemical phosphorus removal units
    The BCFS process avoids the unfavorable conditions of biological phosphorus removal by increasing the phosphorus separation process (too long sludge age, too low influent BOP/P ratio); it is easy to obtain extremely low phosphorus removal with biological phosphorus removal supplemented by chemical phosphorus removal.
    The concentration of orthophosphate in the effluent can greatly reduce the amount of COD under the condition of ensuring good effluent quality


    (3) Compared with the UCT process, BCFS has two additional internal cycles, which can assist the return of sludge to replenish nitrate nitrogen to the anoxic tank, and establish a cycle between the aerobic tank and the mixing tank to increase nitrification or simultaneous nitrification and denitrification The opportunity to create conditions for obtaining a good nitrogen concentration in the effluent

    Related Links: New Technology of Biological Nitrogen Removal from Wastewater-Simultaneous Nitrification and Denitrification



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