Centre of Excellence for Ecohydrology, University of Western Australia, c/o DAFWA, 444 Albany Highway, Albany, WA 6330, Australia; School of Civil, Environmental and Mining Engineering, University of Western Australia, M015, 35 Stirling Highway, Crawley, WA 6009, Australia.
Centre of Excellence for Ecohydrology, University of Western Australia, c/o DAFWA, 444 Albany Highway, Albany, WA 6330, Australia; Department of Agriculture and Food, Western Australia, 444 Albany Highway, Albany, WA 6330, Australia; School of Civil, Environmental and Mining Engineering, University of Western Australia, M015, 35 Stirling Highway, Crawley, WA 6009, Australia.
Water Res. 2014 May 15;55:83-94. doi: 10.1016/j.watres.2014.02.019. Epub 2014 Feb 15.
Extremely acidic and saline groundwater occurs naturally in south-western Australia. Discharge of this water to surface waters has increased following extensive clearing of native vegetation for agriculture and is likely to have negative environmental impacts. The use of passive treatment systems to manage the acidic discharge and its impacts is complicated by the region's semi-arid climate with hot dry summers and resulting periods of no flow. This study evaluates the performance of a pilot-scale compost bioreactor treating extremely acidic and saline drainage under semi-arid climatic conditions over a period of 2.5 years. The bioreactor's substrate consisted of municipal waste organics (MWO) mixed with 10 wt% recycled limestone. After the start-up phase the compost bioreactor raised the pH from ≤3.7 to ≥7 and produced net alkaline outflow for 126 days. The bioreactor removed up to 28 g/m(2)/d CaCO3 equivalent of acidity and acidity removal was found to be load dependent during the first and third year. Extended drying over summer combined with high salinity caused the formation of a salt-clay surface layer on top of the substrate, which was both beneficial and detrimental for bioreactor performance. The surface layer prevented the dehydration of the substrate and ensured it remained waterlogged when the water level in the bioreactor fell below the substrate surface in summer. However, when flow resumed the salt-clay layer acted as a barrier between the water and substrate decreasing performance efficiency. Performance increased again when the surface layer was broken up indicating that the negative climatic impacts can be managed. Based on substrate analysis after 1.5 years of operation, limestone dissolution was found to be the dominant acidity removal process contributing up to 78-91% of alkalinity generation, while bacterial sulfate reduction produced at least 9-22% of the total alkalinity. The substrate might last up to five years before the limestone is exhausted and would need to be replenished. The MWO substrate was found to release metals (Zn, Cu, Pb, Ni and Cr) and cannot be recommended for use in passive treatment systems unless the risk of metal release is addressed.
在澳大利亚西南部，存在天然的强酸性和高盐地下水。随着农业对当地植被的大规模开垦，这种水被排放到地表水中的情况有所增加，很可能会对环境产生负面影响。由于该地区气候半干旱，夏季炎热干燥，导致经常断流，因此使用被动处理系统来管理酸性排放及其影响变得复杂起来。本研究评估了在半干旱气候条件下，一个中试规模的堆肥生物反应器处理强酸性和高盐度排水的效果，该生物反应器的运行时间长达 2.5 年。生物反应器的基质由城市有机废物（MWO）与 10wt%回收石灰石混合而成。在启动阶段后，堆肥生物反应器将 pH 值从≤3.7 提高到≥7，并在 126 天内产生净碱性流出物。生物反应器去除了高达 28g/m(2)/d 的 CaCO3 当量的酸度，并且在第一年和第三年发现酸度去除与负荷有关。夏季长时间的干燥和高盐度导致在基质顶部形成一层盐-粘土表面层，这对生物反应器的性能既有好处也有坏处。表面层防止基质脱水，当生物反应器中的水位在夏季低于基质表面时，确保基质保持水淹状态。然而，当水流恢复时，盐-粘土层会在水和基质之间形成障碍，降低处理效率。当表面层被打破时，性能再次提高，这表明可以控制负面的气候影响。根据运行 1.5 年后的基质分析，发现石灰石溶解是去除酸度的主要过程，其对碱度生成的贡献高达 78-91%，而细菌硫酸盐还原产生的碱度至少占总碱度的 9-22%。在石灰石耗尽之前，基质可能还可以使用长达五年的时间，届时需要补充。MWO 基质被发现会释放金属（Zn、Cu、Pb、Ni 和 Cr），除非解决金属释放的风险，否则不能推荐其用于被动处理系统。
