Department of Civil and Environmental Engineering, Imperial College London, SW7 2AZ, UK.
Department of Civil and Environmental Engineering, Imperial College London, SW7 2AZ, UK.
J Environ Manage. 2021 Feb 15;280:111658. doi: 10.1016/j.jenvman.2020.111658. Epub 2020 Nov 24.
Thermal processes for the treatment of faecal sludge such as pyrolysis or combustion offer complete destruction of pathogens, whilst allowing for energy and nutrient recovery. The development of such processes is currently constrained by a lack of knowledge on thermally relevant faecal sludge characteristics. This study investigated thirty faecal sludge samples from three sanitation technologies (ventilated improved pit latrines (VIP), urine diverting dry toilets (UD), septic tanks (ST)) and compared these by non-parametric statistical analysis. A focus was placed on parameters necessary for thermal process development and recoverable nutrient concentrations. The relevant characteristics ranged widely within technology groups. Calorific values and ash concentrations of 2.1-25.7 MJ/kg and 9.5-88.4% were observed for STs, of 9.2-13.9 MJ/kg and 40.9-61.5% for VIPs and of 3.9-18.1 MJ/kg and 18.8-81.3% for UDs. These two parameters show a strong linear inverse correlation and determine the minimum dewatering requirements from which a net energy recovery may be possible. Results suggest that more than 90% of samples can meet these requirements following commonly used dewatering technologies. A comparison across technologies provided strong evidence that the faecal sludge source significantly influences sludge composition, emphasized by higher median ratios of fixed carbon to volatile matter in VIPs (0.23) and UDs (0.23) compared to STs (0.15). The sanitation technology also influenced recoverable nutrient concentrations, with phosphorus and potassium concentrations generally ranging between 5.8-49.2 g/kg and 1.4-26.1 g/kg respectively. Compared to STs, median concentrations of phosphorus and potassium in VIPs were 3.4 and 3.8 times higher respectively, and 3.0 and 8.8 times higher in UDs. The findings highlight the importance of considering the faecal sludge source in the development of thermal treatment processes. This study provides critical knowledge to further develop such processes through modelling, experimental and scaled approaches.
粪便污泥的热处理方法，如热解或燃烧，可以彻底破坏病原体，同时实现能源和营养物质的回收。然而，这些方法的发展目前受到对热相关粪便污泥特性缺乏了解的限制。本研究调查了来自三种卫生技术（通风改良坑式厕所（VIP）、尿液分流干式厕所（UD）、化粪池（ST））的 30 个粪便污泥样本，并通过非参数统计分析对这些样本进行了比较。研究重点放在热工艺开发和可回收营养物浓度所需的参数上。在所研究的技术组内，相关特性的范围很广。观察到 STs 的热值和灰分浓度为 2.1-25.7 MJ/kg 和 9.5-88.4%，VIPs 为 9.2-13.9 MJ/kg 和 40.9-61.5%，UDs 为 3.9-18.1 MJ/kg 和 18.8-81.3%。这两个参数呈强烈的线性反比关系，并决定了可能实现净能量回收的最低脱水要求。结果表明，经过常用的脱水技术，超过 90%的样品可以满足这些要求。不同技术之间的比较提供了强有力的证据，表明粪便污泥的来源显著影响了污泥的组成，VIPs（0.23）和 UDs（0.23）中固定碳与挥发性物质的中位数比明显高于 STs（0.15），这一点得到了强调。卫生技术还影响可回收营养物浓度，磷和钾的浓度通常分别在 5.8-49.2 g/kg 和 1.4-26.1 g/kg 之间。与 STs 相比，VIPs 中磷和钾的中位数浓度分别高出 3.4 倍和 3.8 倍，UDs 中分别高出 3.0 倍和 8.8 倍。研究结果强调了在开发热处理工艺时考虑粪便污泥来源的重要性。本研究为通过建模、实验和规模化方法进一步开发这些工艺提供了关键知识。
