| So far, the high Ca2+ wastewater is mainly generated by petroleum processing section, non-ferrous metal smelting and another chemical industry. The most typical is gelatin production wastewater. The Ca2+ and CO32- in the waste water will produce CaCO3 in activated sludge process, generating a lot of CaCO3 will not only affect settlement ability, adsorption capacity, mass transfer, SRT of the sludge, but also cause secondary waste-huge excess sludge emissions. This problem will increase the treatment cost of high Ca2+ waste water. So it is imperative to explore the cost-effective sludge reduction program to solve this problem. Nowadays, the main measures of sludge reduction contains high dissolved oxygen method, OSA technology law, ozone method, micro organisms, wet- oxidation two-phase techniques and so on.In our previous study, the scale inhibitor PESA was added into high Ca2+ wastewater to reduce the accumulation of CaCO3 and the sludge activity and its reduction improved. PESA is a green scale inhibitor which have double efficacy of corrosion inhibition and scale inhibition. The application of the PESA to the treatment of the calcium phosphorus waste water, on the one hand, it can form a soluble chelate with Ca2+ and disperse in water, on the other hand, it can restrain the growth of calcium precipitation depositing in sludge surface which caused by the biological aeration and improve the sludge volume ratio(SV30), adsorption capacity, settlement ability, mass transfer, and sludge retention time(SRT) efficiently. Besides that, the excess sludge emissions will be reduced effectively.Given the problem of high concentration of Ca2+ and PESA effect on enzyme activities and microbial communities, in this paper, we assessed the effect of Calcium and PESA on effluent of pH, SVI, MLSS, MLVSS, biofacies, ash, F value, four kind of enzyme activities, microbial communities and diversity, and all of their variation, to test whether the PSEA own compatibility in biological systems and verify the activate recover of sludge when Calcium sludge disperse by PESA. The results showed that when Ca2+ concentration at the range of 0~1920 mg/L, the effluent pH and SV30 of activated sludge declining, MLSS and MLVSS rised, the catalase activity decreased from 2.3 to 0.5 mg/(g·min), the phosphatase activity were:2325-4579-2394 μg/(g·h), the urease activity were:105-56.5-70.6-39.51 μg/(g·h), the protease activity were:6.81-14.28-3.49- 14.22-0.73 mg/(g·h), F value declined from 0.86 to 0.69, the ash rised from 402 to 1890 mg/L; all these show that when the activated sludge systems of ρ(Ca2+) arrived at 1920 mg/L, four kind of enzyme activities were inhibited, so obtained that the inhibition point of Calcium on activated sludge can be identified as 1920mg/L. We kept the system calcium concentration unchanged while the concentration of Ca2+ arrived at the inhibition point 1920 mg/L, and the PESA(5-25 mg/L) was constant gradient added, the the activity of catalase decreased from 0.5 to 0.3 mg/(g·min), the phosphatase rose from 2394.8 to 9336.7 μg/(g·h), urease rose from 39.51 to 82.31 μg/(g·h), the activity of protease kept almost unchanged, F values was maintained about 0.7, the ash content declined from 1890 to 1358 mg/L. Results indicated that all enzyme activities declined with the increase of Ca2+, the microbial growth and activity were also affected, thereby the secretase of enzyme decreased gradually, the ash of sludge increased lead to the amount of sludge rose up; and when PESA was added, some types of enzymes activity such as phosphatase and urease got restored, the ash of sludge and the amount of sludge declined. It could prove that the soluble chelates dispersed in water, let the calcium salt sediments reduced, the enzymes activities restored and achieved sludge reduction.At the same time, the activated sludge DNA were isolated from the 0.5-1.0g centrifuged samples of phase 0(0mg/L Ca2+), 9(1920mg/L Ca2+), 14(25mg/L PESA), the V3-V4 region of bacterial 16 S rDNA gene were sequenced and analyzed, there were 19 phylum levels of species in 0 phase activated sludge, it was relatively abundant, and it dominant species were Bacteroidetes(45.7%), Proteobacteria(34.1%), Planctomycetes(7.1%), TM7(3.1%), Verrucomicrobia(4.2%), Firmicutes(0.9%); until the ninth phase, disappeared four species, only has 15 phylum levels of species,and the dominant species were Bacteroidetes(39.7%), Proteobacteria(39.1%), Planctomycetes(6.8%), Verrucomicrobia(4.7%), TM7(2.6%), Firmicutes(2.7%), Actinobacteria(1.2%); until the ninth phase fourteenth, it has 13 phylum levels of species, disappeared three species, and the dominant species were Bacteroidetes(49.8%), Proteobacteria(38%), Planctomycetes(1.6%), TM7(6.8%), Actinobacteria(1.9%) and Chloroflexi(0.8%). Even though the dominant species of three phase were the same, but the proportion were far different, the major proportion of Bacteroides has improved, some of the bacterium were continued die out, analysis of the microbial community demonstrated that high concentration of calcium ions and PESA altered the distribution of microbes within the community and have no significant on microbial diversity during reactor operation, according to Illumina MiSeq sequencing analysis. |
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