Bioelectrochemistry applications for recovery and production of valuable resources from wastewater and organic waste

这项工作的长期目标是展示将不想要的废物(废水污泥、食物垃圾和烟道气)可持续地转化为有价值的产品(NH4+和生物塑料)。这种转化需要大量的能源消耗和其他资源(例如，用于生物塑料生产的有机酸)。为了使这种转化可行，我们将研究微生物电解槽(MEC)、双极膜电渗析(BMED)和微生物PHA(生物塑料的聚羟基烷基聚合物材料)积累，并实现以下短期目标。 1.从有机废物中分离NH4+和挥发性脂肪酸(VFA)的能耗降低 2.一株高效积累PHA微生物的选择性培养 3.微生物将二氧化碳转化为PHA的可持续氢气供应 BMed由双极膜(BPM)和离子交换膜(IEM)组成，通过阴离子交换膜(AEMS)分离VFA(乙酸酯、丙酸)共轭碱，通过阳离子交换膜(CEM)分离NH4+，生成酸碱溶液(本工作中为VFA和NH4+溶液)。液体废渣(本工作中从高温处理的废水、污泥和食物垃圾中分离出来的液体废水)将在BMED中处理，以产生VFA和NH4+溶液。为了减少电能消耗，BMED将被整合到MEC中，在MEC中，外生细菌通过VFA氧化产生电流。 富营养罗氏菌是一种高效积累PHA的细菌(占菌体干重的80%-90%)，但目前尚无从混合培养物中选择性培养富营养化乳杆菌的方法。因此，它们不适合于利用生物活性废水(如液体沼液)中的有机物生产PHA。在这项工作中，我们将利用富营养化杆菌的另一种独特能力，既可以异养生长(有机碳为碳源)，也可以自养生长(二氧化碳为碳源)。通过重复地交替自养和异养条件，我们假设，在混合培养中可以选择性地富集富营养化细菌，而其他异养和自养细菌则表现出有限的生长。从BMED中提取的不含NH4+的VFA溶液将用于富营养化细菌培养过程中PHA的积累。 我们将进一步展示利用富营养化的罗氏杆菌培养物将烟气中的二氧化碳自养转化为PHA。MECS将用于供应氢气，从而降低PHA生产成本。来自BMED的VFA溶液将为MEC中的外源提供有机底物，VFA溶液中没有NH4+将触发CO2转化为PHA。 我们的研究成果将使以更低的成本利用有机废物和烟道气生产NH4+和PHA成为可能。从有机废物中回收的NH4+可用于土地化肥制造。利用烟道气生产PHA将减少温室气体(温室气体)排放，因为在加拿大，燃煤/天然气发电厂排放的温室气体约占温室气体排放量的10%。

The long-term objective of this work is to demonstrate sustainable conversion of unwanted wastes (wastewater sludge, food waste, and the flue gas) into valuable products (NH4+ and bioplastics). Such conversions require intensive energy consumption and other resources (e.g., organic acids for bioplastics production). To make such conversions feasible, we will research microbial electrolysis cells (MEC), bipolar membrane electrodialysis (BMED), and microbial PHA (polyhydroxyalkanoateraw material of bioplastics) accumulation with the following short-term objectives. 1. Energy reduction in NH4+ and volatile fatty acid (VFA) separation from organic waste 2. Selective enrichment of a high-capacity PHA-accumulating microorganism 3. Sustainable H2 supply for microbial CO2 conversion into PHA BMED consists of bipolar membranes (BPMs) and ion exchange membranes (IEMs) to produce an acid and base solutions (VFA and NH4+ solutions in this work) by separating conjugate bases of VFAs (acetate, propionate) through anion exchange membranes (AEMs) and NH4+ through cation exchange membranes (CEMs). Liquid digestate (liquid wastewater separated from thermophilically pretreated wastewater sludge and food waste in this work) will be treated in BMED to produce the VFA and NH4+ solutions. To reduce electric energy consumption, BMED will be integrated in MECs where exoelectrogenic bacteria generate electric current from VFA oxidation. Ralstonia eutropha is high-capacity PHA-accumulating bacteria (80-90% of dry cells); however, there are no methods for selective enrichment of R. eutropha from a mixed culture. As a result, they are not suitable for PHA production using organics in biologically active wastewater (e.g., liquid digestate). In this work, we will utilize another unique capability of R. eutropha that can grow either heterotrophically (organic carbon as carbon source) or autotrophically (CO2 as carbon source). By alternating autotrophic and heterotrophic conditions repetitively, we hypothesize that R. eutropha can be selectively enriched from a mixed culture while other heterotrophs and autotrophs show limited growth. The VFA solution without NH4+ from BMED will be used to induce PHA accumulation during R. eutropha enrichment. We will further demonstrate autotrophic conversion of CO2 in the flue gas into PHA using the enriched R. eutropha culture. MECs will be used to supply H2, reducing the cost for PHA production. The VFA solution from BMED will provide organic substrates to exoelectrogens in the MECs and the absence of NH4+ in the VFA solution will trigger conversion of CO2 into PHA. Our research outcomes will make it feasible to utilize organic waste and the flue gas for NH4+ and PHA production at reduced costs. NH4+ recovered from organic waste can be used for land fertilizer manufacturing. PHA production from the flue gas will reduce GHG (greenhouse gas) emission as coal/natural gas power plants are responsible for ~10% of GHG emission in Canada.