| Water shortage has been becoming one of the most intractable problems in the world, which is an obstacle to the social and economic development of our country. Wastewater reuse is an effective way to mitigate the growing conflict between water demands and water shortages. "Ozone- biological filter" is one of the classic processes in wastewater reuse, but its decontamination capacity is mainly influenced by the ability of the biofilter. Conventional fillers such as quartz sand, anthracite, etc. have many disadvantages like a smooth surface, small specific surface area, low adsorption capacity, uneasy to attach for microorganism and so on. Therefore modifying the filter is effective to improve the removal efficiency of biofilter. In this study, there was a contrast among nature sand biofilter, hydrophilic modification sand biofilter, hydrophobical modification sand biofilter and iron modification sand biofilter on the removal of pollutants during the start-up and stable period. And the best ozone dosage was determined. The removal of conventional pollutants and 3 target Ph ACs were tested by "ozone- nature bio-sand filter", "ozone- hydrophilic modification bio-sand filter", "ozone- hydrophobical modification bio-sand filter" and " ozone- iron modification bio-sand filter" under the optimum operating conditions.The results indicated that the dissolved organics were dominating since the dissolved COD accounted for 78.77%~86.62%、74.92%~83.79% and 83.57%~90.32% respectively in secondary effluent of A, B and C wastewater treatment plants. The secondary effluent is poorly biodegradable in three wastewater treatment plants since the BOD5/CODCr were 0.211 ~ 0.303 、 0.207 ~ 0.290 ' 0.184 ~ 0.239, respectively. TN and NH3-N in secondary effluent of A, B plants can barely reach the standard requirements. TP in three WWTPs also do not reach the standard requirements. In a word, dissolved pollutants are the main removal target and it is necessary to adopt chemical oxidation as a pre-treatment unit for the secondary effluent because of poorly biodegradable.8 target Ph ACs were detected in secondary effluent of A, B, C WWTPs with concentrations ranging from ng/L to μg/L. Based on MEC/PNEC evaluation system, the risk assessments in accordance with the most disadvantaged the principles showed that SMZ, OFX, ERY-H2 O and TCN belonged to high risk, MET and CBZ belonged to moderate risk and the rest belonged to low risk in effluent of A WWTP. OFX, ERY-H2 O and SMZ belonged to high risk, TCN belonged to moderate risk and ROX, CIP, MET and CBZ belonged to moderate risk and the rest belonged to low risk in effluent of B and C WWTPs. The RQ(sum) for 8 target Ph ACs of three WWTPs were 138.03, 254.78 and 143.65 respectively. According to the most disadvantaged the principles, it led to a high risk in water environment.It was indicated that when ozone dose was 2mg/L, HRT in ozone tank was 15 min and hydraulic loading was 5.0 m3 /(m2?h) in bio-sand filters, "ozone-hydrophilic modification bio-sand filter" and "ozone- iron modification bio-sand filter" were best at removing NH3-N with average removals 88.25% and 87.40% respectively. "Ozone- nature bio-sand filter" and "ozone- hydrophobical modification bio-sand filter" average removals were 73.07% and 71.81% respectively. "Ozone- hydrophobical modification bio-sand filter" was best at removing UV254 with average removal 29.24%., The CODcr removal rates by "Ozone- nature bio-sand filter", "ozone- hydrophilic modification bio-sand filter", "ozone- hydrophobical modification bio-sand filter" and " ozone- iron ion modification bio-sand filter" were 19.39%, 31.56%, 19.80% and 30.00% respectively.The average removals of CIP, ERY-H2 O and TCN were 75.99%, 16.63% and 29.38% respectively by ozone. The average removals of ERY-H2 O and TCN were 43.51% and 24.94% respectively by nature bio-sand filter. The average removals of CIP by hydrophilic modification and iron modification bio-sand filter were 68.24% and 60.59% respectively. The average removals of TCN by hydrophilic modification and iron modification bio-sand filter were 25.67% and 24.75% respectively. And the average removals of ERY-H2 O by hydrophilic modification and iron modification bio-sand filter were 19.49% and 21.22% respectively. The removal rates of 3 target Ph ACs were very low by hydrophobical modification bio-sand filter. The average removals of CIP by "ozone- nature bio-sand filter", "ozone- hydrophilic modification bio-sand filter", "ozone- hydrophobical modification bio-sand filter" and "ozone-iron modification bio-sand filter" were 34.37%, 90.45%, 75.49% and 92.26% respectively, the average removals of ERY-H2 O were 52.87%, 34.32%, 24.56% and 32.84% respectively and the average removals of TCN were 46.99%, 46.91%, 28.34% and 47.50% respectively.It was showed that there were 27 phylums and 266 genuses in the samples taken from four bio-sand filters and proteobacteria was dominant. Nitrosomonas was dominant species in AOB bacteria and the abundance of natural, hydrophilic modification, hydrophobical modification, and iron oxide coated sand biofilter samples were 0.96%, 1.47%, 1.30% and 2.56%. Nitrospira was dominant species in NOB bacteria and the abundance of natural, hydrophilic modification, hydrophobical modification, and iron oxide coated sand biofilter samples were 1.90%, 4.75%, 1.88% and 3.77%. |
PDF Full Text Request