Experimental Study On The Ex-Site Treatment Of Malodorous River Water By Expanded Granular Sludge Bed (EGSB) Reactor

In this paper, optimal culture of seed sludges of expanded granular sludge bed (EGSB), denitrification effect of these seed sludges and the start-up and operation performances of EGSB reactor were studied for treating seriously-polluted urban malodorous river. The main experimental results are:(1) In the shaking conical flask experiments for seed sludges optimal culture, after 80～83 day's cultivation, all seed sludges occurred anaerobic ammonia oxidation (ANAMMOX) and showed good denitrification effect on malodorous river water. The average NH4+-N removal efficiencies of Reactor 1 and Reactor 2, both using pumice as carriers, were 35.32% and 30.10%, respectively. The minimum concentration of NH4+-N in the effluents of R1 and R2 reached 9.12 mg/L and 8.91 mg/L, respectively. The average NH4+-N removal efficiencies of R1 and R2 increased by 29% and 20% compared with the other three reactors (R3, R4 and R5). Pumice dosage of 20 g/160 mL and 40 g/160 mL were not obviously different in the removal of NH4+-N.(2) In the field experiment, EGSB reactor inoculated with the relatively optimal cultivated seed sludges started-up successfully. The start-up period lasted about 45～50 d, and obviously ANAMMOX occurred in the latter operation. During the start-up period, the maximum removal efficiencies of CODCr, NH4+-N and TIN reached 22.89%,62.49% and 41.28%,respectively.The minimum concentration of NH4+-N in the effluent was 5.07 mg/L, and the average removal rate of TIN could reach 0.19 kg/m3·d.(3) In the steady running period of EGSB reactor, the maximum NH4+-N removal efficiency and the minimum NH4+-N concentration in the effluent reached 75.54% and 3.01 mg/L; similarly, NO2--N being 99.51% and 0.031 mg/L; NO3--N being 60.41% and 0.96 mg/L. In general, EGSB reactor was effective for nitrogen removal and its contents of nitrogen pollutants in the effluent could approach grade V of the surface water quality standard. The maximum removal efficiency of CODcr was 68.98%and the minimum CODCr concentration in the effluent reached 30.16mg/L, which conformed to the surface water quality standard gradeⅤ:(4) In the major affecting factors of temperature, HRT, reflux ratio were investigated in the running process of EGSB reactor, The optimized working condition was temperature above 10℃, HRT 2h, reflux ratio less than 300% and pH 7.0～8.2.(5) SEM indicated that there were bacterial communities similar with anammox bacteria and methanogen in the sludges of EGSB reactor as previous reported.