| Aerobic granulation is considered to be a promising biotechnology for wastewater treatment, especially for toxic wastewater. Compared with activated sludge, aerobic granular sludge has several advantages including better settling ability,higher density, stronger microbial structure, higher biomass retention, and better nutrient-removing capability. So far, many researchers have achieved aerobic granular sludge from bench-scale and pilot-scale reactors. However, the utilization rate of reagents and the loss of biomass in setup time leading to poor nutrient removal performance need more research.Four sequencing batch reactors (SBRs) seeded with different facilitated-biofilm reagents in dewatered sludge included R1 (without reagent), R2 (alginate), R3 (PAM)and R4 (chitosan). The granulation time of four SBRs was 17days, 23days, 25days and 36days, respectively. The cultivated granules seeded with facilitated-biofilm reagents were more compacted,composed of bacteria aggregates with the structure of pores and channel network without cells, short bacilli were the main microorganisms.The sedimentation velocity in 4 reactors was 0.44 cm/s, 1.03 cm/s, 0.77 cm/s and 1.02 cm/s; the SOUR was 42.64 mg/(g · h), 68.37 mg/(g · h), 55.83 mg/(g · h) and 59.68 mg/(g · h); integrity coefficient was 94.1%?99.1%?97.6% and 97.9%; water content was 97.7%,96.8%,96.5& and 96.2%, respectively.The settling ability of sludge system improved progressively in reactors with alginate, PAM and chitosan and a faster increase in the biomass concentration could be observed in R2 and R4. PAM and chitosan had no influence on EPS content, while the PS in EPS was increased obviously with alginate in the first 7 days. PAM had inhibitory effect on biomass activities at first several days. Nitrite was practically not detected in the treated effluent in each reactor achieving a maximum concentration of 0.02 mg/L. The NO3- effluent concentration in R1 was obviously higher than it in R2 ,R3and R4 when influent concentration of NH4+-N was above 40 mg/L. The removal rate of TN was about 40%, 70%, 60% and 50% respectively when influent concentration of TN was 50mg/L. The degradation kinetics equation of activated sludge and the mature granules in 4 SBRs was:v=0.23S/(183.01+S),v=1.01S/(939.68+S), v=2.31S/(2646.17+S),v=1.62S/(1723.43+S),v=1.26S/(1288.35+S).The COD removal rate of granules seeded with facilitated-biofilm reagents was better than granules in R1 dealing with phenol wastewater. When influent concentration of phenol was 200mg/L,the removal rate of TN was about 40%?60.64%?42.3% and 54%,the removal rate of NH4+-N was about 52%,74.7%,64.5% and 69.5% respectively. The weak structure of granules in R1 occured disintegration when influent concentration of phenol was above 50mg/L. The sedimentation velocity, SOUR and integrity coefficient of granules were decreased and water content was increased obviously. The sedimentation velocity and integrity coefficient of granules seeded with PAM were decreased, while the physical-chemical properties of aerobic granular sludge seeded with alginate and chitosan were remain stable treating 200mg/L phenol wastewater. |
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