生物炭强化模拟废水中高浓度苯酚的微生物降解

Biochar enhances microbial degradation of high concentration phenol in simulated wastewater

采用花生壳生物质废物分别在350、550和750℃条件下限氧热解制备生物炭,之后加入到苯酚污染模拟废水中,验证其强化苯酚微生物降解的效果.结果表明,未加生物炭的系统中,苯酚浓度过低(≤ 110 mg·L^-1)不能使菌体达到最大浓度,苯酚浓度过高(≥ 420 mg·L^-1)则会抑制菌体生长,降解率仅为43.2%,且停滞期长.添加生物炭后,苯酚去除率大幅度提高,在6~16 h时微生物进入对数生长期,苯酚浓度快速降低.2、4和6 g·L^-1的生物炭添加量均可使苯酚在16 h内被完全去除,高添加量的生物炭能吸附39.3%的苯酚,降低其对微生物的毒性抑制.550℃热解温度制备的生物炭取得了最好的强化效果,其pH缓冲作用可中和苯酚降解产生的酸性物质,而750℃热解温度制备的生物炭由于pH过高而使菌体难以存活.生物炭在相对低苯酚浓度下(600、800 mg·L^-1)可显著提高其去除率,分别从29.6%、24.5%升至46.9%、36.9%.而对于初始苯酚浓度高达1000 mg·L^-1以上的系统,则需要海藻酸钙凝胶固定菌体到生物炭才能获得较高的降解率.

Peanut shell waste was pyrolyzed at 350℃, 550℃ and 750℃ under oxygen-starved condition to produce biochar, which was subsequently used as a support for bacterial growth to facilitate phenol degradation. Without biochar, bacteria did not grow well in the presence of phenol at low concentration (≤ 110 mg·L^-1), while their growth was inhibited at higher concentration (≥ 420 mg·L^-1) of phenol, with a prolonged lag phase (about 4 hours) and a noticeable decreased phenol removal efficiency of 43.2%. With biochar, the phenol removal efficiency remarkably improved and the lag phase shortened to 6~16 hours. Phenol was 100% removed within 16 h with biochar dose of 2、4和6 g·L^-1. High biochar dose adsorbed 39.3% of phenol and thus mitigated phenol toxicity to bacteria. Biochar pyrolyzed at 550℃ achieved the greatest phenol removal, possibly resulting from its buffering capability against pH drop due to the accumulation of acidic intermediates during phenol degradation. However, biochar pyrolyzed at 750℃ completely inhibited bacterial growth due to its extremely alkaline pH. Biochar substantially increased the efficiency of phenol removal from 29.6% to 46.9% at initial concentration of 600 mg·L^-1 and from 24.5% to 36.9% at initial concentration of 800 mg·L^-1, respectively. However, to obtain phenol removal with initial concentration >1000 mg·L^-1, enhanced bacterial immobilization by calcium alginate gel would be essential for ideal degradation efficiency.