| Iron, manganese and ammonia are common inorganic pollutants present in groundwater. To address the water scarcity issue and advance the traditional drinking water treatment technique, a powered activated carbon-amended membrane bioreactor(PAC-MBR) is proposed for treatment of real groundwater(Mn2+=1.2 mg·L-1, Fe2+=15.0 mg·L-1 and NH4+-N=2.2 mg·L-1). Three lab-scale PAC-MBR system were carried out to purify d ifferent amount of pollutants and operated for 230 days. The influent of the PAC-MBR systems were three ones, one was raw water directly, the other two were pretreated by conventional bio-sand filters.Firstly, in order to obtain various effluent of bio-sand filters, which were used as the influent of PAC-MBR system. Aeration before bio-sand filters was used to control the dissolved oxygen(i.e. 9 mg·L-1 and 6 mg·L-1) of filters influent. The results showed the effluent concentrations of iron, manganese, ammonia is less than 0.12 mg·L-1, 0.1 mg·L-1 and 0.02 mg·L-1, respectively, in the case of high dissolved oxygen(9 mg·L-1), the type of filters media(i.e. quartz sand and manganese sand), exhibited a slightly effect on the removal of iron and manganese water and ammonia especially in the early period. However, when the dissolved oxygen was lower(6 mg·L-1), the effluent concentrations of iron, manganese, ammonia were 0.15 mg·L-1, 0.2 mg·L-1 and 1.0 mg·L-1, respectively, the two media showed no significant differences in the removal of iron, manganese, ammonia.Secondly, in three PAC systems treating different account of pollutant, the manganese and ammonia concentration of effluent can reach 0.05 mg·L-1 and 0.02 mg·L-1, respectively. The influent iron concentration of the two system treating bio-sand filters effluent, was 0.08 mg·L-1, while the concentration of iron was less than 0.15 mg·L-1, which influent was raw water. Increasing the dosage of PAC(from 1 g·L-1 to 4 g·L-1), the start-up period of manages will be reduced from 45 days to 40 days while there was no effect on ammonia star-up period. Increasing the concentration of pollutants will increase start-up period, the start-up period of iron, manganese and ammonia would change from 45 to 48 days, from 45 to 50 days, from 20 to 35 days, respectively.In addition, the membrane fouling of different PAC-MBR systems was various under 222 days operation. we found that in a single system treating different amount concentration of pollutants, such as the system with PAC dosage 2 g·L-1, it presented that a slight increase(9.1 k Pa) during the first 140 days treating the effluent of bio-sand filters whereas the membrane fouling was severely and the changed TMP was 36 k Pa during the last 80 days treating raw water. In different systems with different amount of PAC dosage(i.e. 1 g·L-1 and 4 g·L-1), higher PAC dose exhibited a good performance in membrane fouling control in the case of treating bio-sand filters effluent and the TMP increase was only 10.4 k Pa under 222 days operation time. Considering the ratio between PAC and pollutants, the lowest membrane fouling occurred under the conditions of higher PAC dose and lower account of pollutants in bio-sand filters effluent. With respect to chemical cleaning drug, oxalic acid was an better choice.Furthermore, our present work analyzed microbial species using high-throughput sequencing, including four samples, manganese sand whose dissolved oxygen is 9 mg·L-1 and 6 mg·L-1, respectively, the membrane samples whose PAC dosage is 4 g·L-1, which influent is after the filtration,the membrane whose PAC dosage is 2 g·L-1. Specially, results from high-throughput sequencing analysis revealed that Hyphomicrobium, Flavobacterium, Planctomyces, Nitrosomonas were dominant in the bio-sand filters whereas Leptothrix, Pseudomonas and Nitrosomonas played major roles in PAC-MBR systems for the removal of pollutants. |
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