| As a main technique for the leachate treatment, anaerobic biodegradation has been widely used, anaerobic granular sludge is the key point of anaerobic biological treatment effect. Humic Acid (HA for short) is the major component of refractory organic compounds in landfill leachate, whose content will increase significantly with the increase of the landfill time. In order to better understand the effects of HA in leachate on the anaerobic granular sludge, The anaerobic biodegradability of HA as well as the influences of different HA concentration on specific methanogenic activity (SMA), shape and structure of granular sludge in anaerobic treatment was studied in the condition of both simulated water and actual leachate through home-made anaerobic reaction system. The basis could be provided for anaerobic biological treatment of landfill leachate.The results indicate that the HA don’t have obvious effect on anaerobic granular sludge, the main conclusions are obtained as follows:(1) The results of HA anaerobic biodegradability show that as a refractory organic compounds, HA is also hard to be decomposed and utilized by microbes in the anaerobic process. The presence of HA and the corresponding concentration variety will not present obvious biological toxicity inhibition on granular sludge. On the contrary, because of the maintain function of HA on the shape of granular sludge, It could delay the decomposition and release of granular sludge, then increase the decomposition utilization of granular sludge on the organic pollutants in landfill leachate.(2) The effect of HA on SMA of granular sludge shows that the presence of HA and the corresponding concentration variety will not have significant influences on the total cumulative methane production and the anaerobic methanization process. Furthermore, on the basis of complete reaction, the total cumulative methane production can not reflect the inhibitory effect of the toxics on the SMA of granular sludge. Otherwise, toxic and harmful substances in the leachate play obvious inhibition role on the granular sludge. The cumulative methane production after 20h was up to 75% in control groups without leachate, with only 25% of cumulative methane production in experiment groups in the presence of leachate. It is indicated that sufficient reaction time is necessary to achieve better effects in the anaerobic biological treatment of leachate. Comparing the SMA of granular sludge, it is known that HA has certain promoting effect on the SMA of granular sludge. In the absence of buffering agent, the SMA value increased by 19.2% on average, while in the presence of buffering agent, the SMA value increased by 5.4% on average. However, in the presence of leachate, the SMA value decreased by 27.6% on average, because the hazardous effect of toxics in the leachate on the sludge is far greater than the promoting effect of HA.(3) The influence of HA on the shape and structure of granular sludge shows that appearance structure of granular sludge didn’t change obviously after the experiments comparing to that of inoculation sludge. However, the microbial biomass on the surface and in the internal of the sludge significantly increased. Microorganisms on the surface of the sludge take coccus as main, while the internal takes filamentous bacteria. HA has no obvious effect on the shape and structure of granular sludge without buffering agent, but the surface and internal microbial species and number are higher than those in control groups. When the buffering agent added, the effect of HA on morphological structure and microbial components in sludge is not obvious. Because of the complexity of the water quality, the hole structure on the surface and in the internal of granular sludge is reduced in the presence of leachate, but the effect of HA on the morphological structure and microbial components of granular sludge is not obvious. |
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