| Most of the urban rivers in North China are lack of basic flow,and these rivers bear the discharge function of urban tail water.These rivers which lack of base flow and heavily polluted have become a typical feature of the rivers in North China.The governance of this heavily polluted river was a worldwide problem.The best way to solve this problem is impreving the ecological utilization rate of urban reclaimed water.Jialu River,a typical urban river lacking of base stream and polluted seriously,is lack of natural runoff and maintain its basic flow of water by accepting the city tail water of Zhengzhou.Since 2007,after 10 years of governance,conventional water quality of Jialu River,such as chemical oxygen demand(COD)and ammonia nitrogen(NH3-N),has been significantly improved through the basin of large-scale use of recycled water for ecological supply.As there is still much containment in the reclaimed water,the large-scale utilization of reclaimed water in Jialu River may still pose ecological risks,such as long-term exposure toxicity effect and cumulative effect to aquatic lives.So,they are three questions need to be resolved in Jialu River water quality improvement project:Firstly,the environmental health and the species diversity of Jialu River are need to be investigated;Secondly,the toxicity effects in Jialu River are need to be investigated;Thirdly,the reduction of toxicity effect in the secondary effluent of the wastewater plants by advanced treatment process are need to be studied.To solve above problems,this study has evaluated species diversity in Jialu River,ecological risk of Jialu River and reduced the toxicity effect by advanced treatment process.And the results are summarized as follows:(1)The algae abundance in the main section of the Jialu River(J0-J3)was from 0.71 ×106 to 16.39×106 ind/L,and almost all species of phytoplankton are mainly blue algae and green algae which can indicating water pollution.Zooplankton are mainly small zooplankton(protozoa and rotifers),accounting for 84.9%of the total,and the variation range of the Shannon diversity index was from 0.86 to 2.88.The biodiversity data shows that reclaimed water discharged into Jialu river are still pose ecological risk.(2)The vitro toxicity test includes estrogenic activity,androgenic activity,genotoxicity and dioxin-like toxicity,and the estrogenic activity,furthermore,the genotoxicity was used in the ecological risk assessment of water samples.The results show that estradiol(E2)values of environmental estrogenic activity of J0 and J1 water samples were from 2.03 to 6.22 ng/L,which was 2-5 times of predicting no effect concentrations(PNEC)values of E2,showing some environmental estrogen toxicity effect.The zebrafish exposed to water samples was also applied in the ecological risk assessment of water samples.And the transcription level of 14 genes in hypothalamus-pituitary-gonads(HPG)axis in 14 d exposed zebrafish larvae also shows that the JO and J1 water samples posed estrogenic activity to zebrafish larvae.At the same time,male zebrafish that exposed to JO and J1 water samples for 120 days has shown that the transcription level of vtgl and vtg3 was significantly affected by endocrine disruptor chemicals,which could be used as biomarker in further studies.Due to replenishment in upstream of the Jialu River(JO and J1)mainly from the municipal wastewater treatment plant effluent,therefore,it is necessary to study advanced treatment processes(ATPs)to reduce the estrogenic activity of the municipal wastewater treatment plant effluent.The SOS/umu assay in vitro showed that the 4-nitroquinoline-1-oxide(4-NQO)equivalent value of the J3 water samples was 4.2± 0.3 μg/L.This value was about 6.5 times of the PNEC value of 4-NQO,and presents obvious genetic toxicity effect.After "Embryo-young fish" continuous exposure 14 days and "embryonic zebrafish larvae-adult male" continuous exposure 120 days by animal experiment,the 8-OHdG concertation in zebrafish exposed to J3 has shown that the J3 water samples were posed obvious genotoxicity effect.The replenishment in J3 section mainly came from the papermaking wastewater in Shuangji River.Therefore,it is necessary to study advanced treatment processes to reduce the genotoxic of papermaking wastewater.(3)The effluent of Wulongkou municipal wastewater treatment plant of Zhengzhou City was the main sewage discharge source of the JO and JI section.So,the vitro toxicity,including estrogenic activity,androgenic activity,genotoxicity,dioxin-like toxicity,the estrogenic activity and the genotoxicity in the secondary effluent was tested,and the results of the estrogenic activity(E2 equivalent)was 6.26±0.21 ng/L,which means the secondary effluent may pose estrogenic activity risk to aquatic lives.Many studies had reported the ATPs’ removal efficiency of pollutants in wastewater,however,treatment conditions of the effluents and ATPs in these literatures varied and making them hard to compare.First,secondary effluent from the Wulongkou municipal wastewater plant was tested for its toxicity effects before and after five ATPs,including coagulation sedimentation,activated carbon adsorption,NDMP resin adsorption,ozonation and electro-adsorption.The results showed that estrogenic activity were particularly significant for the raw secondary effluent among the studied dioxin-like toxicity effects,androgenic/anti-androgenic activity,estrogenic activity,and genotoxicity effects.And estrone(El),E2 and EE2 were the main endocrine disruption chemicals as contribute to estrogenic activity.Except coagulation sedimentation,the other four ATPs were efficient in the E1,E2,and EE2(steroid estrogens)removal,but these ATPs were inefficient in the octyl-phenol(OP),bisphenol A(BPA),and dibutyl phthalate(DBP)removal.In the ATPs treated samples,vtg in zebrafish was largely removed.However,they were still significant as comparison with the control,which probably due to OP,BPA and DBP.Ecological restoration project is also an effective way to treat the municipal wastewater and improve the water quality of urban rivers.This study also investigated the efficiency of reducing estrogenic activity in reclaimed municipal wastewater along Suoxu River(an 18.5 km field-scale ecological restoration project),which is a branch river of Jialu River.Suoxu River only receives secondary effluent of Wulongkou municipal wastewater plant.Data show that COD and NH3-N of the Suoxu River improved compared to the Chinese surface water standard,E1 and E2 were effectively removed during ecological restoration purification processes.The estrogenic activity was less than 0.01 ng/L after the ecological purification of restoration river;however,OP,BPA,and DBP were difficult to eliminate.However,21d exposure in vivo test of zebrafish showed that exposure to the reclaimed municipal effluents,even after river purification,still significantly induced vtg and E2 in male zebrafish.This indicates continued potent estrogenic activity to aquatic organisms,even after treatment and purification(4)The value of 4-NQO of the effluent of papermaking wastewater treatment plant was 27.4±2.2 μg/L,which was nearly 50 times of the PNEC value of 4-NQO.To remove genetic toxicity,the "Fenton fluidized bed " advanced treatment process was applied in genotoxicity effect removal,and the different dosage of pH 0%H2O2 dosage,mol ratio(H2O2/FeSO4)and the genotoxicity effect removal rate were also considerate.At the pH = 3.5,the hydrogen peroxide dosing quantity = 1.4 mL and the molar ratio of hydrogen peroxide and ferrous sulfate = 4:1,the TOC reduction efficiency of per liter secondary effluent water may reached to 71.3%and the reduction of genetic toxicity is 54.0%.Although the genotoxicity effect was effectively removed,the acute toxicity effect was obviously increased after"Feton-fluidzed bed" treatment process and the coagulating sedimentation process treated.Considering all of these results,the artificial test was used after the coagulating sedimentation process to removal the acute toxicity effect in water.Based on small scale test results talked above,A "Fenton fluidized bed-coagulation sedimentation-artificial wetland purification" project was built in the sewage treatment plant and used to treat the secondary effluent,the acute toxicity of tail water from medium toxicity reduced to non-toxic,and the genetic toxicity reduced 80.7%.In combination with the results of three-dimensional fluorescence spectra,the reduction of genetic toxicity was positively correlated with the reduction of protein-like substances in water.Finally,the concentration of 8-OHdG in zebrafish exposed in all water samples for 21d has shown that the genotoxicity of secondary effluent can be remarkable reduced after the Fenton-oxidation coagulation precipitation in the wetland treatment processes. |
