The reasons leading to the excessive total phosphorus in biological phosphorus removal effluent involve many aspects, mainly including:
(1) Sludge load and sludge age
Anaerobic-aerobic biological phosphorus removal process is a system with high F/M and low SRT. When F/M is high and SRT is low, the discharge of excess sludge will be more. Therefore, under the condition of a certain phosphorus content in sludge, the more phosphorus is removed, the better the phosphorus removal effect is.
For biological systems whose main purpose is phosphorus removal, the SRT is 10 ~ 15d. However, the SRT should not be too low, and the effective removal of BOD5 must be ensured.
(2) Biochemical oxygen demand/total phosphorus
In order to ensure the phosphorus removal effect, BOD5/TP in the sewage entering the anaerobic zone should be controlled to be greater than 20. Because polyphosphate belongs to Acinetobacter, its physiological activity is weak, and it can only absorb the easily decomposed part of organic matter. Therefore, the content of BOD5 in influent should be ensured to ensure the normal physiological metabolism of phosphorus accumulating bacteria. However, there are low-carbon sources and high concentrations of nitrogen and phosphorus in the actual influent of many urban sewage treatment plants, which leads to the BOD5/TP value can not meet the needs of biological phosphorus removal and affects the effect of biological phosphorus removal.
(3) Dissolved oxygen
The anaerobic zone should be kept in a strict anaerobic state, that is, the dissolved oxygen is lower than 0.2mg/L, and then the phosphorus accumulating bacteria can effectively release phosphorus to ensure the subsequent treatment effect. However, the dissolved oxygen in aerobic zone should be kept above 2.0mg/L, so that phosphorus accumulating bacteria can effectively absorb phosphorus. Therefore, improper control of dissolved oxygen in anaerobic zone and aerobic zone will greatly affect the effect of biological phosphorus removal. In addition, the influent of some sewage treatment plants is river water, and the dissolved oxygen content in sewage is high. If it directly enters the anaerobic zone, it will not be conducive to the control of anaerobic state and affect the phosphorus release effect of phosphorus accumulating bacteria.
(4) Reflux ratio
The reflux ratio of anaerobic-aerobic phosphorus removal system should not be too low, and it is necessary to maintain enough reflux ratio to discharge the sludge in the secondary sedimentation tank as soon as possible to prevent phosphorus accumulating bacteria from releasing phosphorus in the anaerobic environment of the secondary sedimentation tank. On the premise of ensuring rapid sludge discharge, the reflux ratio should be reduced as much as possible to avoid shortening the actual residence time of sludge in the anaerobic zone and affecting the release of phosphorus.
In the anaerobic-aerobic phosphorus removal system, if the sludge sedimentation performance is good and the reflux ratio is in the range of 50 ~ 70%, the sludge can be discharged quickly.
(5) Hydraulic retention time
The hydraulic retention time of sewage in anaerobic zone is generally between 65438±0.5 ~ 2.0h The retention time is too short, on the one hand, it can't guarantee the effective release of phosphorus, on the other hand, facultative acidification bacteria in sludge can't fully decompose macromolecular organic matter in sewage into lower fatty acids for phosphorus accumulating bacteria to absorb, which also affects the release of phosphorus.
The residence time of sewage in aerobic zone is generally 4 ~ 6 hours, which can ensure the full absorption of phosphorus.
(6) pH value
Low pH is beneficial to the release of phosphorus, high pH is beneficial to the absorption of phosphorus, and the effect of phosphorus removal is the combination of phosphorus release and absorption. Therefore, in the biological phosphorus removal system, the pH value of the mixed solution should be controlled in the range of 6.5 ~ 8.0. Due to the increasing demand for total phosphorus in effluent, in addition to biological phosphorus removal, chemical phosphorus removal has been applied more and more. However, chemical phosphorus removal can not only improve the phosphorus removal effect, but also greatly increase the amount of excess sludge and treatment cost due to the addition of chemical agents. Therefore, the combination of biology and chemistry is a reasonable choice at present.
Using the wisdom of sewage treatment to run the workstation, on the basis of improving biological phosphorus removal to the greatest extent by breathing atlas technology, a small amount of chemical phosphorus removal agent is added according to the effluent quality, which not only ensures the effluent to meet the standard, but also saves a lot of reagent costs.
Intelligent operation workstation for sewage treatment-monitoring the growth process of microorganisms by using a series of patented technologies, and realizing early warning of sludge health, various microbial growth states, excessive COD, excessive ammonia nitrogen, excessive total phosphorus and sludge bulking. And analyze the key objectives. The whole process is completely completed automatically by the equipment and cloud expert system, and at the same time, it provides operational suggestions for customers and escorts the safe and stable operation of sewage treatment plants.