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

Since the 1980s, biological removal of ammonia and phosphorus technology has made significant developments
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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.

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
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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.

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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
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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.

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.

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

(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