Study On Start-up And Stable Operation Of Aerobic Granules System Based On Swine Wastewater Treatment

Swine wastewater has the characteristics of high organic and nitrogen content, pathogens and antibiotic residues. The content of nitrogen and phosphorus easily caused eutrophication, which will pollute the water environment. So before discharge, we must treat swine wastewater, in order to remove the carbon nitrogen phosphorus and other pollutants. According to the characteristics of swine wastewater, the common treatment method is the anaerobic process. The effluent ammonia concentration after anaerobic treatment is still high, so how to handle the higher ammonia concentration after anaerobic in swine wastewater has become an urgent problem. Aerobic granules with good settling performance, has the strong capacity of anti-shock loading and can adsorb heavy metals and toxic substances, can realize simultaneous nitrification and denitrification is a better choice, which can solve this problem. Therefore, the study researches start-up and stable operation of aerobic granules system, which based on swine wastewater treatment.We can activate the aerobic granules systems by simulating swine wastewater and real swine wastewater. We firstly start the aerobic granules systems by simulated swine wastewater manual configuration in different pressure conditions, in order to obtain a better selection pressure condition. The study found that, when the pressure conditions are in three different options, aerobic granule systems can all start successfully. But the amount of aerobic granules which the size is larger than 1cm particles is different in each proportion. When the selection pressure is greater, the proportion of larger particles is smaller. The extracellular polymeric substance (EPS) and the content of organic matter in the sludge (VSS/SS) changes have little impact in the sludge of different selection pressures. But the zeta potential of sludge in smaller pressure reactor is lowest, the sludge is more stable. Small selection of granular sludge pressure conditions can cultivate strong stability. SEM pictures showed that the successful cultivation of granular sludge surface smooth by spherical bacteria, aerobic granules in the three reactor can be cultured successfully. Therefore, the system which is in smaller selection pressure have the best condition. Then, we choose the best drainage ratio. When the drainage ratio were 73%,66% and 50%, we are all successful start aerobic granules system under the condition of actual swine wastewater. There is no difference between the three kinds of formation of granular sludge under the condition of the process. When the drainage ratio is 66%, the content of extracellular polymeric substance of mature granular sludge is higher, but its Zeta potential is the lowest. When the drainage ratio is too large, a large number of bubble is produced, sludge loss is serious, and the drainage ratio is relatively small, this phenomenon has been effectively suppressed. The carbon and nitrogen removal rate of aerobic granules in the drainage ratio of 66% is better, and the drainage ratio of 50% have good phosphorus removal rate. Comprehensive consideration of various factors, drainage ratio of 66% is the best starting conditions.In the stable operation stage, we select three kinds of different drainage ratio (75%,50% and 25%) during the experiment. When the drainage ratio are 75% and 50%, the proportion of large granular sludge increased, the sludge size becomes larger. The protein (PN), polysaccharides (PS) and EPS of sludge increased slightly, the PN/PS ratio change is not big. The granular sludge is full and dense, dark and black. SVI5 and VSS/SS have little change. The spherical bacteria has completely occupied the dominant position in aerobic granules, the two systems can successfully run stably. The two systems have similar nitrogen and phosphorus removal efficiency, Nitrogen and phosphorus removal rate is high and stable. But when the drainage ratio is 25%, the proportion of large granular sludge has been reduced, the loss of sludge and disintegration phenomenon have emerged, the content of EPS increases suddenly, the color of the sludge particle edge slightly white, the white flocculent sludge is increased. The nitrogen removal rate is slow, the condition is not suitable for aerobic granules treatment of swine wastewater. Therefore, the drainage ratio of 75% and 50% are the operation conditions. Research shows that, when the pH values are7.0±0.1,7.5±0.1 and 8.0±0.1, aerobic granules for swine wastewater treatment system can stable operation. The diameter of granular sludge, the nature and the apparent morphology of sludge have little difference. The difference of granular sludge in EPS, polysaccharides, protein, Zeta potential, SVI5 and VSS/SS were not obvious. But under the three condition, the nitrogen and phosphorus removal efficiency are different. When the pH value was 8.0±0.1, the nitrogen removal effect is best, the rate of removal of nitrogen and phosphate removal efficiency are high, so 8.0±0.1 is the best condition for stable operation of pH.