تصفیه تکمیلی شیرابه کمپوست با استفاده از راکتور ناپیوسته متوالی (SBR)

As a result of penetration of water in landfills through precipitations and or by conducting some processes such as size reduction of waste materials as well as biodegradation of materials in composting process, leachate may be produced. High organic loading and containing complex and various compounds introduce leachate as a toxic wastewater and a risk for the environment. With respect to relatively high organic load and existing refractory organic compounds, a single process cannot remove all of the organic matters from leachate. Therefore, to meet discharge standards, additional treatment is required to remove the remaining materials from treated leachate. In addition, Sequencing Batch Reactor (SBR) is a reliable biological treatment applied to eliminate pollutant from leachate and spread in the worldwide. As a result post-treatment of composting leachate via SBR was chosen as the main objective of this study. This study was conducted in laboratory scale and in batch mode. The working volume of SBR reactor was 1.3 L. A complete cycle of SBR is divided into five stages, include to fill, react (mixing & aeration), settle, draw, and idle. The SBR system and duration of five stages were automatically controlled. Sludge bulking is a common problem in biological treatment. For controlling of sludge bulking different parameters such as DO, pH and temperature were adjusted in a fixed range. Furthermore, due to better control of sludge bulking, sometimes H2O2 solution was injected to the reactor. In this study, performance of the SBR system were analyzed according to sludge retention time (SRT) and hydraulic retention time changes. SRT was adjusted to 3, 5 and 7 days and hydraulic retention time was increased from 4 hr. to 6,8,10 and 12 hr., respectively. The leachate samples were collected from the effluent of anaerobic biological reactor of a composting leachate treatment facility in north of Iran. The seed samples were supplied from a wastewater treatment plant in Tehran and acclimatized with diluted leachate. The SBR reactor operated with 1L of leachate and 300 ml of acclimatization seed. The mean initial COD and color were 2000 mg/L and 5.7 Gardner, respectively. Performance of the SBR system was monitored by analyzing the COD and color removal efficiency, determining of MLSS and MLVSS changes and estimating the waste sludge production. In this research, optimum SRT and hydraulic retention time for SBR system were estimated to be 5 days and 12 hours, respectively. Based on the results, the maximum removal efficiency of COD and color in SBR process were estimated to be 90% and 44% respectively, that reduced the initial COD from 2184 mg/L to 215 mg/L and closed to the Iranian standard discharge limits for agricultural purpose. In this process, values of waste sludge production were also analysed respected different hydraulic retention times. The results revealed that by increasing the hydraulic retention time, waste sludge production was decreased. Finally, different kinetic models such as first order, Grau and Stover-Kincannon were examined for the optimal condition. The kinetics studies showed that post-treatment of leachate by SBR processes were in good agreement with the Grau and Stover-Kincannon kinetic models by a correlation coefficient of more than 97%.