Impacts of backwashing on micropollutant removal and associated microbial assembly processes in sand filters

● Backwashing in sand filters with 2-h and 4-h EBCTs was simulated. ● Removal efficiency of five micropollutants recovered within 2 d at 2-h EBCT. ● Active biomass of sand filters recovered within 2 d under two EBCTs. ● Microbial composition gradually recovered to pre-backwashing level at 2-h EBCT. ● Recovered microbes only accounted for 15.55 %–25.69 % in the sand filters at 4-h EBCT. Backwashing is crucial for preventing clogging of sand filters. However, few studies have investigated the effect of backwashing on micropollutant removal and the dynamic changes in the microbial community in sand filters. Here, we used a series of manganese and quartz sand filters under empty bed contact times (EBCTs) of 2 h and 4 h to explore variations in micropollutant degradation and temporal dynamics of the microbial community after backwashing. The results showed that the removal efficiencies of caffeine, sulfamethoxazole, sulfadiazine, trimethoprim, atrazine, and active biomass recovered within 2 d after backwashing in both types of sand filters at 2-h EBCT, but the recovery of sulfadiazine and trimethoprim was not observed at 4-h EBCT. Moreover, the removal efficiency of atenolol increased after backwashing in the manganese sand filters, whereas maintained almost complete removal efficiency in the quartz sand filters at both EBCTs. Pearson correlation analysis indicated that microbial community composition gradually recovered to the pre-backwashing level (R increased from 0.53 to 0.97) at 2-h EBCT, but shifted at 4-h EBCT (R < 0.25) after backwashing. Furthermore, the compositions of the recovered, depleted, and improved groups of microbes were distinguished by applying hierarchical clustering to the differentially abundant amplicon sequence variants. The cumulative relative abundance of recovered microbes at 2-h EBCT was 82.76 % ± 0.43 % and 46.82 % ± 4.34 % in the manganese and quartz sand filters, respectively. In contrast, at 4-h EBCT, the recovered microbes dropped to 15.55 %–25.69 % in both types of sand filters.     

用DWZ接触氧化处理工艺处理屠宰废水

实行畜禽定点屠宰后，含有大量有机污染物的畜禽屠宰废水的处理问题急需解决，经浙江省海宁市某畜禽屠宰厂运行证实，采用DWZ接触氧化处理工艺，具有投资少，占地面积小，处理效果好，抗冲击能力强，操作简便，运行费用低等特点，废水经处理后可达到GB8978－1996 Ⅰ级排放标准，得到了社会各界的广泛好评，本文主要介绍了该处理设施的处理工艺，运行特点及优越性，提供一条治理畜禽宰废水的有效途径。     

曝气生物滤池工艺处理瓷厂污水

瓷厂污水中的污染物主要以有机物为主,可生化性较好,易于用生物法处理.采用曝气生物滤池(BIOFOR)工艺处理瓷厂污水.其污水水质:ρ(CODCr))为400mg·L-1;ρ(BOD5)为200 mg·L-1;ρ(NH3-N)为35mg·L-1;ρ(SS)为300 mg·L-1.运行结果表明,该工艺处理效率高、操作简单、运行费用低、占地面积小,出水水质达到了《污水综合排放标准》(GB 8978-1996)一级排放标准.     

Comparisons of the film peeling from the composite oxides of quartz sand filters using ozone, hydrogen peroxide and chlorine dioxide

To solve the problem of shortened backwashing intervals in groundwater plants, several disinfectants including ozone (O₃), hydrogen peroxide (H₂O₂) and chlorine dioxide (ClO₂) were examined to peel off the film from the quartz sand surface in four pilot-scale columns. An optimized oxidant dosage and oxidation time were determined by batch tests. Subsequently, the optimized conditions were tested in the four pilot-scale columns. The results demonstrated that the backwashing intervals increased from 35.17 to 54.33 (H₂O₂) and to 53.67 hr (ClO₂) after the oxidation treatments, and the increase of backwashing interval after treatment by O₃ was much less than for the other two treatments. Interestingly, the treatment efficiency of filters was not affected by O₃ or H₂O₂ oxidation; but after oxidation by ClO₂, the treatment efficiency was deteriorated, especially the ammonia removal (from 96.96% to 24.95%). The filter sands before and after the oxidation were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. Compared with the oxidation by O₃ and H₂O₂, the structures on the surface of filter sands were seriously damaged after oxidation by ClO₂. The chemical states of manganese on the surfaces of those treated sands were only changed by ClO₂. The damage of the structures and the change of the chemical states of manganese might have a negative effect on the ammonia removal. In summary, H₂O₂ is a suitable agent for film peeling.