Source Tracing Of The Adsorbable Organic Halogens In The Hangzhou Bay And The Research On Its Removal Technology

Adsorable Organic Halogens?AOX?is a sum indicator deteming the total amount of organically bound halogens in the environment.The AOX discharge was attached increasing attention.The Hangzhou Bay was arounded by tens of large industrial park,which made the Hangzhou Bay become one of the most polluted areas in China.This study focused on the contamination status,the source tracing and the removal technology of the AOX in the Hangzhou Bay.AOX concentration in samples collected from the Hangzhou Bay in 2014,2015 and 2016 was detected to understand the AOX contamination status of the Bay.The result showed that seawater of the Hangzhou Bay contains140.6±45.6⁷16.1±62.3?g/L AOX,which was much higher than the concentrations reported in other areas indicating that the Hangzhou Bay was seriously polluted by AOX.However,the AOX content in the sediment,11.3±2.4¹12.7±7.2 mg/kg,was relatively lower than that detected in the sediment of Finland Bay.Eleven WWTPs were selected as important terrestrial point sources of pollutants of the Hangzhou Bay to understand the contribution of the AOX from the terrestrial source since the capacity of those WWTPs covered 64.7%of the total capacity of all WWTPs around the Hangzhou Bay,The results showed that industrial wastewater was the main source of AOX while the demostic wastewater was not.Over 645.5 t AOX was discharged into the Hangzhou Bay from those WWTPs,of which the WWTP?,treating the wastewater from a national industrial park,covered 21.3%.The AOX detection of 20 factories of 4 main industries of the park showed that the pharmaceutical wastewater was an AOX polluted wastewater containing 2.8⁶12.5 mg/L AOX which was higher than other wastewater.The A/A/O system was used to treat the selected AOX-bearing pharmaceutical wastewater.The results showed that the system could achieve a removal efficiency of 73.1±11.2%,87.7±24.5%,99.1±0.5%,73.4±12.1%for AOX,COD,NH₃-N and TN,respectively,under the optimal operation parameter,total HRT of 62.5 h,the reflux ratio of 2 and DO of 3-4 mg/L.Electric was employed to enhance the AOX removal effect of the anerobic process.The results showed that the AOX removal efficiency was enhaced to 75.2%when the cathode was polarized to-1000 mV,and the AOX could be further reduced to 100 mg/L when the effluent was treated by the aerobic process.Nonetheless,the AOX still couldnot match the standard,thus the Fenton process was used to treat the effluent of aerobic process to make sure the AOX concentration could be reduced to lower than 8 mg/L which matched the standard of the park as well as TOC.The tetrachlorbenzene?TeCB?was selected as a typical AOX compound in the pharmaceutical wastewater and treated in the anaerobic microcosm.It was found that the TeCBs could be reduced to dichlorbenzene in the microcosm.The double flanked chlorine was the easiest one to be removed and the isolate chlorine was the hardest one.The microbial community morphology and structure of anaerobic sludge was studied.The abundance of the microorganism having a function of dehalogenation was 43.91%,46.63%and 38.35%in sludge from anaerobic process of A/A/O,BER?BE?and microcosm?MC?,respectively.The structure of community was similar,the Desulfovibrio,Dehalobacter,Dehalococcoides,Desulfomicrobium,Geobacter,Desulforhabdus were the most important dehalogenation bacteria.