Shih Justin, Fanyin-Martin Ato, Taher Edris, Chandran Kartik
Earth and Environmental Engineering, Columbia University, New York, NY, 10027, USA.
Chemical Engineering,, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
Gates Open Res. 2017 Nov 6;1:10. doi: 10.12688/gatesopenres.12754.1.
In Ghana, faecal sludge (FS) from on-site sanitation facilities is often discharged untreated into the environment, leading to significant insults to environmental and human health. Anaerobic digestion offers an attractive pathway for FS treatment with the concomitant production of energy in the form of methane. Another innovative option includes separating digestion into acidogenesis (production of volatile fatty acids (VFA)) and methanogenesis (production of methane), which could ultimately facilitate the production of an array of biofuels and biochemicals from the VFA. This work describes the development, implementation and modeling based analysis of a novel multiphase anaerobic fermentation-digestion process aimed at FS treatment in Kumasi, Ghana. A pilot-scale anaerobic fermentation process was implemented at the Kumasi Metropolitan Assembly's Oti Sanitary Landfill Site at Adanse Dompoase. The process consisted of six 10 m reactors in series, which were inoculated with bovine rumen and fed with fecal sludge obtained from public toilets. The performance of the fermentation process was characterized in terms of both aqueous and gaseous variables representing the conversion of influent organic carbon to VFA as well as CH . Using the operating data, the first-ever process model for FS fermentation and digestion was developed and calibrated, based on the activated sludge model framework. This work represents one of the first systematic efforts at integrated FS characterization and process modeling to enable anaerobic fermentation and digestion of FS. It is shown that owing to pre-fermentation of FS in public septage holding tanks, one could employ significantly smaller digesters (lower capital costs) or increased loading capabilities for FS conversion to biogas or VFA. Further, using the first-ever calibrated process model for FS fermentation and digestion presented herein, we expect improved and more mechanistically informed development and application of different process designs and configurations for global FS management practice.
在加纳，现场卫生设施产生的粪便污泥（FS）常常未经处理就排放到环境中，对环境和人类健康造成了严重危害。厌氧消化为FS处理提供了一条有吸引力的途径，同时还能以甲烷的形式产生能源。另一种创新选择是将消化过程分为产酸阶段（挥发性脂肪酸（VFA）的产生）和产甲烷阶段（甲烷的产生），这最终可能有助于从VFA生产一系列生物燃料和生化产品。这项工作描述了一种新型多相厌氧发酵 - 消化工艺的开发、实施及基于模型的分析，该工艺旨在处理加纳库马西的FS。在阿丹斯·东波阿塞的库马西大都会议会奥蒂卫生填埋场实施了中试规模的厌氧发酵工艺。该工艺由六个串联的10米反应器组成，接种了牛瘤胃，并以从公共厕所获得的粪便污泥为原料。发酵过程的性能通过代表进水有机碳转化为VFA以及CH₄的水相和气态变量来表征。利用运行数据，基于活性污泥模型框架开发并校准了首个FS发酵和消化过程模型。这项工作是对FS进行综合表征和过程建模以实现FS厌氧发酵和消化的首批系统性努力之一。结果表明，由于FS在公共污水储存池中进行了预发酵，人们可以使用显著更小的消化器（降低资本成本），或者提高FS转化为沼气或VFA的负载能力。此外，使用本文提出的首个经过校准的FS发酵和消化过程模型，我们期望在全球FS管理实践中，不同工艺设计和配置的开发与应用能得到改进且更具机械原理依据。
