Conference Proceeding

Exploiting anaerobic digestion to facilitate reuse of treated water and resource recovery.

,
With increasing population, demand for fresh water is ever increasing. Contamination of water resources have led to a condition where currently over 15% of the world population (about 1.2 billion) lack access to safe potable water. Growing scarcity of fresh water reserves and ever increasing demand for water have led to a condition where the option of reuse of treated wastewater cannot be ignored any more. Innovative wastewater treatment plants aiming not only at treating the wastewater, but also providing other benefits such as facilitating reuse of treated water, resources recovery or nutrient reuse – depending on the local context – are the need of the day. Conventional sewage treatment processes involve high land requirement or capital, maintenance and operational cost, huge energy requirements, which makes them unsuitable for use in developing countries. Energy efficient low-cost wastewater treatment systems are the best choice for such countries. Anaerobic treatment systems excel in such respect. A pilot-scale up flow anaerobic sludge blanket-moving bed biofilm (UASB-MBB) reactor followed by a high rate algal pond (HRAP) was designed and operated to remove organic matter, nutrients and pathogens from sewage and to facilitate reuse. The black water after treatment in UASB-MBBR-HRAP is being reused for gardening and landscaping. A novel hybrid up flow anaerobic sludge blanket - moving bed biofilm reactor followed by rope bed biofilm reactor (UASBMBBR- RBBR) was designed and operated for about a year to achieve removal of organic matter and nitrogen from sewage. The hybrid UASB-MBBR-RBBR technology could thus provide an alternative, low maintenance, economical and efficient system for simultaneous carbon and nitrogen removal and energy recovery, which is not otherwise possible using conventional secondary sewage treatment processes. In a microbial fuel cell (MFC), organic compounds are oxidized by microorganisms, and the electrons generated from this oxidation can be used to produce energy and other value added products. Successful sulphate and COD removals from synthetic wastewater with wide range of COD and sulphate concentrations as well as sulphate rich sewage added products. Successful sulphate and COD removals from synthetic wastewater with wide range of COD and sulphate concentrations as well as sulphate rich sewage along with simultaneous energy harvesting were explored in a MFC with recovery of elemental sulphur. Results and mass balance of COD and sulphate indicate that this type of MFC is a promising scalable system for actual applications, which can achieve almost 72% of elemental sulphur recovery from sulphate laden wastewater. A major limitation to achieve higher power output from MFC is the development of competitive environment for substrate utilization offered by methanogenic Achaea. A study revealed the comparative electrical performance of MFC, where the enrichment of anodic electrogenic , inoculum was done with two low-cost peptaibiotics recovered from Trichoderma sp. The inhibitory effect on methanogens was sustained even after 15 batch cycles of MFC operation, demonstrating no adverse effect of such peptaibiotics on electro gens, but providing a non-competitive environment for their growth by effectively inhibiting methanogens and considerably enhancing the power recovery from MFC. Performance of a baked clayware membrane MFC inoculated with mixed anaerobic sludge pre-treated with Alaric acid was investigated in order to enhance power recovery by controlling methanogenesis. Addition of lauric acid significantly achieved suppression of methanogenesis and enhanced the sustainable power generation of MFC by 3.9 times as compared with control MFC inoculated with sludge without any pre-treatment. For sustaining power production and enhancing Columbic efficiency (CE) of MFC, studies were conducted to inhibit cathodic befouling using different loadings of silver nanoparticles (Ag-NPs) with 5% and 10% Ag in carbon black powder. The results suggest that the Ag-NPs effectively inhibit the fungal biofouling on cathode surface of MFCs and enhanced the power recovery and CE by improving cathode kinetics. Catalytic effect of goethite recovered from iron-ore mining mud was studied in MFCs. Characterization of material recovered from mining mud confirms the recovery of iron oxide as goethite. Cheaper goethite coating kinetically accelerates the electron transfer between bacteria and anode, proving to be a novel approach for enhancing the electricity generation along with organic matter removal in MFC. 22 - 23 MAY 2017 KUALA LUMPUR, MALAYSIA Speaker Performance of scalable air-cathode MFC of 26L volume, made from clayware cylinder with multiple electrodes, was evaluated. Long term operational stability (14months) demonstrates the technical viability of clayware MFC for practical applications and potential benefits towards wastewater treatment and electricity recovery. During scale-up of MFC, a proportional increment in power does not usually occur. A systematic approach is proposed for area (Aan) of an MFC. With wastewater of chemical oxygen demand (COD) of 5 g L-1 and considering a Columbic efficiency and a COD removal of 80% each, a anode chamber volume of 2.02 L is optimum for a single anode chamber to produce a current up to 750 mA; which is the maximum possible current estimated from electromotive force equation. Adopting this volume for each anode chamber in a MFC stack is recommended for treating wastewater under the assumptions of the analysis. Charge transfer kinetics dominates the minimum Aan required, which satisfies the area required for biofilm formation, MFC polarization, and mass transfer. The minimum Aan should be provided in a MFC to ensure the dominance of electro genesis. An attempt has been made to provide solution for distillery wastewater using fungal pre-treatment followed by an anaerobic process to achieve higher organic matter removal, which is a challenge at present with currently adopted technologies. A chitosan recovery of 0.072–0.078 kg/kg of dry mycelium was obtained using dilute sulphuric acid extraction, showing high purity and characteristic chitosan properties according to FTIR and XRD analyses.

Published: 01 August 2017

Copyright:

Copyright: © 2017 Makarand Ghangrekar. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.