Wastewater Treatment Technology Study Based On Enhanced Phosphorus And Nitrogen Removal And Low Sludge Yield

There exist their own disadvantages among all sludge reduction technologies, which mainly contain much oxygen demand and worse removal effect of nitrogen and phosphorous. Therefore, aiming at the mentioned problems, this paper develops a lower sludge yield water treatment process , hydrolysis-acidogenosis-Anaerobic/Anoxic- Multistep Continuous Oxic tank, which can enhance phosphorous and nitrogen removal. The biological treatment unit is composed by the processes of hydrolysis-acidogen; Multistep series aeration and Continuous flow A2/O. This Paper has been systematically studied on the new wastewater treatment and sludge reduction process. the main contents and conclusions are as follows:①Under the low temperature operating conditions, HA-A2O system can improve stablily the VFA in the sewage. By returning aerobic sludge to the acidification tank. Keeping stability of the sludge concentration in the control system, due to the two factors, which are low temperature and the bad compatibility of the dominant bacteria in the acidification sludge and excess sludge, when adjusting the aerobic sludge returning ratio is 3%, is the maximum, VFA hydrolysis produces can not satisfy the carbon demand for phosphorus and nitrogen removal of the follow-up A2O system. The HA-A2O process has a better effect of organic removal; the removal rate of COD is 96%. Due to low temperature and carbon constraints, the system has poorer nitrogen and phosphorus removal, the average removal rate of NH3-N and TN are 78.6% and 65.4%. Lower temperature and limited carbon source lead to phosphorus removal in low rate, and the TP removal rate is only 62%.the relatively long SRT (60d) operation of HA-A2O system allows the system sludge apparent yield is 0.198gMLSS/gCOD, the efficiency of sludge reduction is not obvious, comparing with the existing sludge reduction technology.②Aiming at the impact of returning aerobic sludge on the effect of hydrolysis acidification in hydrolysis acidification-A2O process, and based on hydrolysis acidification-A2O process, HA-A/A-MCO process is developed. By returning part of the anaerobic phosphorus release sludge to hydrolytic acidification tank, changing complete mixing aeration tank to multistage contact aeration tank. Research shows that, when SRT= 60d, sludge activity can be maintained, the sewage treatment system efficiency is meted and smaller sludge discharge is gotten in HA-A/A-MCO system. On this condition, the sludge yield is 0.1gMLSS/gCOD.d on stable operation, which is 1/4 of conventional activated sludge process. 1)On the condition of SRT=60d, COD=316- 407mg/L, NH3-N =30-40mg/L, TN=35-53mg/L, TP =8-12mg/L, the effluent quality reaches the first grade standard of GB18918-2002. 2)comparing the impact of the form of returning sludge on hydrolysis acidification,it is found more helpful to acid hydrolysis when returning the anaerobic phosphorus release sludge to hydrolysis tank. When anaerobic phosphorus release sludge is returned to hydrolysis tank, which the equivalent of 2% inflow quantity. The hydrolyzate VFA concentration is 4.74 times compared to the raw water, so that the competition conflicts of carbon source in phosphorus and nitrogen removal system has been solved. 3)Lateral flow phosphorus removal process can solve the problem of low phosphorus removal efficiency in the HA-A/A-MCO system by discharging anaerobic phosphorus release wastewater, which has low efficiency of phosphorus removal because of low sludge yield. It is further found that in the case of enhancing phosphorus release lateral flow phosphorus removal process, the HA-A/A-MCO system have a strong potential for excess phosphorus uptake and a strong anti-shock phosphorus load capacity. 4)Under the impact of sludge hydrolysis riching VFA, the average phosphorus release concentration is 57mg/L in anaerobic tank of the HA-A/A-MCO system. In the comprehensive consideration of P balance,phosphorus release liquid, 13% of inflow quantity is treated by lateral flow chemical phosphorus removal,and in chemical phosphorus removal tank control the effluent phosphorus concentration is 5mg/L,it not only can improve the utilization of chemical medicament but also increase the phosphorus quantity of chemical sludge. It is found that using lime to fix phosphorus, the phosphorus ratio of chemical sludge is as high as 18%, to effective phosphorus (P2O5) can up to 40%, so it has a higher recycling value.③It has found that the major way of nitrogen removal is aerobic denitrification in the HA-A/A-MCO system,and takes 50% proportion in total nitrogen efficiency, while the rate of anoxic denitrification is 26%. There are some aerobic denitrifying bacterias(such as Z3 and Z10) in the system which have denitrification ability in aerobic conditions through the analysis of biological floras. Under low DO concentration operation, denitrification is not influence by the DO concentration, and this is helpful to form the anoxic environment in sludge flocculant in the aerobic conditions, to promote the SND.In this way, it has positive significance in ensuring the effect of nitrogen in the system. ④In biological wastewater treatment system, under the premise of without affecting system nitrification, the increased influent organic loading helps to improve nitrogen removal rate, while low organic loading is conducive to sludge reduction, and sludge yield is low. It is Found, the critical organic load of HA-A/A-MCO process is 0.141~0.162g/g.d. With lateral flow ratio increases, the system phosphorus removal rate increases. When lateral flow ratio is about 15%, the effluent phosphorus concentration is began to less than 0.5mg/L; With lateral flow ratio increases,the amount of chemical phosphorus removal and removal rate increases, while biological phosphorus removal capacity and removal rate is reduced gradually. Phosphorus removal and sludge reduction are the best, when SRT = 60d, and phosphorus removal rate is 97.6%, the sludge production rate is only 0.11gSS/gCOD.⑤Analysis by PCR-DGGE shows that diversity of microorganisms are really high in hydrolysis acidification tank, anaerobic tank, anoxic tank andaerobic tank, multistep series aerobic tank, interaction of multi- dominant bacteria promote acid production phosphorus and nitrogen removal and sludge reduction performance. Fusobacterium is one of the main bacteria which react on acid production and sludge reduction in the hydrolysis acidification tank, Lactococcus is obligate hydrolysis and acidogenic bacteria. Fusobacterium, Bacillus and Lactococcus, which have the function of acid production, is the reason why hydrolysis acidification tank has a higher VFA production when returning anaerobic phosphorus release sludge. As a result of the high resistance on predacity from advanced microbe, Acinetobacter and Spirochaeta kept stable distribution, the former was the base of good phosphorus removal capacity, while the latter has the function of degradation of organic pollutants. The technologic parameters and environmental condition of bacterial culturing district was propitious to some bacterial growth and propagation, such as Bacillus and Lampropedia. And they can be disappeared as food sources of higher organisms in protozoa and metazoan growth area, at the same time a lower sludge yield, about 0.1kgMLSS/kgCOD, can be reached by increasing higher level of microbial growth density, the growth of micro-classification of animals and higher microorganisms predation on lower predation of microorganisms⑥Because HA-A/A-MCO system has longer SRT and lower load leads to lacking of biodegradable organic, SOUR in HA-A/A-MCO reactor is low, while this phenomenon is not caused by miniature animal predation. Microbial predation in the system not only reduce sludge yield but also enhance settling characteristics of suspended sludge. Rotifer is considered as organism indicating settling capability of suspended sludge in the system, and it is positive correlation between them. Rotifers and erythema floating body insects are considered as organism indicating sludge yield in the system, and it is negative correlation between them.⑦In the aerobic tank of HA-A/A-MCO system, especially the No.2 and No.3 aerobic tank, where has large number of rotifer, erythema floating body insects and other larger metazoan. These organisms can make more large sludge flocs and biofilm looserely relying on their own activities. And it helps to delivering and transferring the oxygen to the internal of sludge flocs with large size and deep of the biofilm, improving oxygen transferring and utilization, making HA-A/A-MCO system achieve ideal effects of synchronous decontamination and sludge reduction in the low-oxygen conditions.It shows that HA-A/A-MCO technology developed not only has better effect of phosphorus and nitrogen removal, but also has better effect of sludge reduction. This technology is a wastewater and sludge treatment technology with cleaner production concepts and resources circulation features. Research results have strong innovation, remarkable academic significance and practical value, which can provide technical support to promote the use of this technology.