藻类对垃圾填埋场渗滤液的净化

Molecular Identification of Algae and Their Use in Landfill Leachate Purification

采用 PCR及序列测定的方法 ,对两个分别分离自广州市李坑垃圾填埋场的渗滤液收集塘以及广州市郊的一个普通池塘的藻类种群的 r DNA ITS区进行了序列的测定和分析 ,结果证实两者均为蛋白核小球藻 ,分别记作 Chlorellapyrenoidosa ( LK)和 Chlorella pyrenoidosa ( P)。将上述两个藻类种群的纯培养液分别接种至一系列不同浓度的垃圾渗滤液中 ,以研究它们在渗滤液中的生长、对渗滤液的耐性以及对渗滤液中污染物的去除等差异。结果表明 ,藻类的生长在1 0 %的渗滤液中都得到了一定的促进 ,而在更高浓度的渗滤液中则受到抑制。但 C.pyrenoidosa( LK)在经过一段时间的适应后 ,对 30 %的渗滤液表现出较强的耐性。藻类的生长使垃圾渗滤液中的 NH3 -N、PO4 -P和 COD等污染物的含量显著下降 ,而 NO3 -N含量下降不明显。

Many studies demonstrated the success of employing algal cultures to remove nutrients from wastewater rich in nitrogenous and phosphorus compounds.Until recently,very little specific work has been focused on landfill leachate treatment using microalgae.The main objective of this study was to identify two microalgal strains of different origins by applying molecular techniques,and examine their growth in landfill leachate and ability to remove the nutrients.;Two algal strains were isolated respectively from the leachate in the surface recirculation pond at Likeng Landfill,Guangzhou,and an ordinary,less polluted pond in the same city.After DNA extraction,sequences of internal transcribed spacers(ITS)of their rDNA were successfully amplified,and the amplification products were used directly for sequencing.They were both identified as Chlorella pyrenoidosa by comparative analysis of the ITS sequences,and named Chlorella pyrenoidosa(LK) and Chlorella pyrenoidosa(P),respectively.;Leachate samples were collected from the surface recirculation pond at Likeng Landfill,and immediately filtered with 0.45 μm membrane filters.They were subsequently diluted to a series of concentrations using sterile deionized water,and inoculated aseptically with stock cultures of Chlorella pyrenoidosa(LK) and Chlorella pyrenoidosa(P)previously grown in Bold's Medium and in exponential phase.Meanwhile,a series of the same concentrations of leachate without any algal inoculations were used as the controls for nutrient removal test.All treatments were in triplicates.At every 1~2 days interval,the algal growths were monitored and compared with those of the same strain grown in Bold's Medium,in terms of increase in cell density counted by a haemocytometer.Aliquots of leachate were sampled every 3 days from each treatment,and analyzed for NH + 4-N,PO 3- 4-P,COD and NO - 3-N. Enhanced growths were found for both Chlorella pyrenoidosa(LK) and Chlorella pyrenoidosa(P)in 10% leachate,and their cell densities went up to 81 and 105 times over its initial values.Higher leachate concentrations were roughly toxic to algae.However,Chlorella pyrenoidosa(LK)showed an obvious tolerance to 30% leachate,after a 10-day period of adapting.Under this leachate condition,it had a better growth and was more effective in nutrient removal than Chlorella pyrenoidosa(P).;Removal rates of NH + 4-N,PO 3- 4-P and COD under all treatments,especially in lower dilution series,were obviously higher than those in the control groups.For example,after a 12-day growth,Chlorella pyrenoidosa(LK) could remove up to 76.1,75.8 and 71.6% of NH + 4-N,PO 3- 4-P and COD from 10% leachate,respectively.While the values for Chlorella pyrenoidosa(P)were 66.2,64.9 and 61.6%,respectively.Meanwhile,no obvious removal was found for NO+--3-N.;The preliminary.results demonstrated the feasibility of using green algae for landfill leachate treatment.Tolerant strains were preferable.Appropriate dilution of pre-treatment of the leachate might be necessary.In combination with traditional techniques in classification,the emerging molecular approaches should play an important role in identifying and screening algal species tolerant to different landfill leachates.