Research On The Treatment Of Coal To Oil Wastewaterby ESGB And SBR Reactors

Coal to oil industry has a great demand of water resource, and is usually located at water deficient areas, which makes the water treatment problem become one of its conditionalitylink of coal to oil industry. In this paper, a wastewater treatment process for the treatment of coal to oil wastewater was designed based on the analysis of typical coal to oil wastewater, and experiments were carried out to determine the parameters of the key process units. Coal to oil wastewater can be divided into synthetic wastewater and coal gasification wastewater. Expanded granular sludge bed reactor(EGSB reactor) was used to treat the synthetic wastewater, and organic compound in syntheticwastewater was collected in the form of biogas energy. Coal gasification wastewater was mixed with the effluent synthetic wastewater of EGSB reactor, and the mixed wastewater was treated by sequencing batch reactor(SBR reactor).Results showed that two-stage EGSB reactor could remove organic compound in the synthetic wastewater efficiently. The influent alkalinity and operation parameter organic load rate(OLR) significantly affected the start-up of the two-stage EGSB reactor. When influent COD concentration was lower than 16000 mg/L, NaOH and NaHCO3 were both needed to adjust influent alkalinity to 2000 mg/L to ensure the buffer capacity of the reaction system. While, alkalinity supplement of NaHCO3 in the influent could be removed at the influent COD concentration exceeding 16000 mg/L, because the anaerobic process could produce enough alkalinity to maintain feasible microbial growth environment. The acceptable operation parameter OLR of the first-stage reactor was below 29 kg COD/(m3?d). Otherwise, high OLR would cause the reactor breakdown. The operating conditions were optimized as the influent pH of 4.8, influent alkalinity of 1200 mg/L, HRT of 37 h, OLR of 26.5 kg COD/(m3?d), COD:N:P of 500:5:1, up flow velocity of 2.0 m/h and proper amount of trace elements should be added. By the treatment of the two-stage EGSB reactor, the COD concentration of synthetic wastewater decreased from 40800 mg/L to 600 mg/L, the removal rate was higher than 98%, and the gas production rate could be as high as 420 L/kg COD.The effluent synthetic wastewater of EGSB reactor and coal gasification wastewater were all refractory organic wastewater. The COD removal rate of the mixed wastewater was only 40.3% by the treatment of SBR reactor. Adding synthetic wastewater into the mixed wastewater could improve the COD removal rate of SBR reactor efficiently. When the dosage of synthetic wastewater was 35 mL/L, the effluent COD concentration was decreased to 203 mg/L, and the removal rate was increased to 89.6%. HRT of anoxic and aerobic process had great impacts on the removal rate of COD, NH3-N, TN and TP. The operating conditions were optimized as operation cycle of 12 h, wastewater inlet time of 5 min, anoxic process of 3 h, aerobic process of 8 h,static settlement of 50 min, water outlet time of 5 min, water drainage quantity of 1/3 reactor volume and total HRT of 36 h. By the treatment of two-stage reactor, the average COD concentration of effluent was 94 mg/L, NH3-N was 0.8 mg/L, TN was 14 mg/L and TP was 0.93 mg/L.By the treatment of Fenton progress, the effluent COD could be controlled under 30 mg/Lwhich meet the first class Arequirements of discharge standard of pollutants for municipal wastewater treatmentplant.