Liam Doherty

A review of a recently emerged technology: constructed wetland - microbial fuel cells.

Constructed wetlands (CWs) and microbial fuel cells (MFCs) are compatible technologies since both are reliant on the actions of bacteria to remove contaminants from wastewater. MFCs require the anode to remain anaerobic with the cathode exposed to oxygen while these redox conditions can develop naturally in CWs. For this reason, research into combining the two technologies (termed as CW-MFC) has emerged in recent years with the aim of improving the wastewater treatment capacity of wetlands while simultaneously producing electrical power. Based on the published work (although limited), this review aims to provide a timely, current state-of-the-art in CW-MFC while exploring future challenges and research directions.

The integrated processes for wastewater treatment based on the principle of microbial fuel cells: A review

abstract Microbial fuel cell (MFC) technology offers the dual advantages of wastewater treatment and electricity generation. Research efforts have been made to improve its power output. However, MFC seems limited at pilot scale and power outputs appear to have plateaued. As such, some integrated technologies have emerged based on MFC. These hybrid technologies have the larger potential for scaling up and practical application compared with the pure MFC. Therefore, in their review the authors present these emerged technologies and discuss the development tendency and the challenges. The review can hopefully provide a framework to identify priorities for further research on this area.

Promoting the bio-cathode formation of a constructed wetland-microbial fuel cell by using powder activated carbon modified alum sludge in anode chamber.

MFC centered hybrid technologies have attracted attention during the last few years due to their compatibility and dual advantages of energy recovery and wastewater treatment. In this study, a MFC was integrated into a dewatered alum sludge (DAS)- based vertical upflow constructed wetland (CW). Powder activate carbon (PAC) was used in the anode area in varied percentage with DAS to explore its influences on the performance of the CW-MFC system. The trial has demonstrated that the inclusion of PAC improved the removal efficiencies of COD, TN and RP. More significantly, increasing the proportion of PAC from 2% to 10% can significantly enhance the maximum power densities from 36.58 mW/m2 to 87.79 mW/m2. The induced favorable environment for bio-cathode formation might be the main reason for this improvement since the content of total extracellular polymeric substances (TEPS) of the substrate in the cathode area almost doubled (from 44.59 μg/g wet sludge to 87.70 μg/g wet sludge) as the percentage of PAC increased to 10%. This work provides another potential usage of PAC in CW-MFCs with a higher wastewater treatment efficiency and energy recovery.

Operating a two-stage microbial fuel cell–constructed wetland for fuller wastewater treatment and more efficient electricity generation

By integrating microbial fuel cells (MFCs) into constructed wetlands (CWs) the need and cost of building a reactor are eliminated, while CWs provide the simultaneous redox conditions required for optimum MFC performance. Two single-stage MFC-CWs, with dewatered alum sludge cake as the main wetland medium for enhanced phosphorus removal, were operated to determine the effects of electrode separation and flow regimes on power production and wastewater treatment. When the anode is buried and the cathode is at the air-water interface the system is inhibited by a large ohmic resistance resulting from the increased electrode separation. By placing the cathode directly above the anode and operating the system with simultaneous up-flow into the anode and down-flow into the cathode the ohmic resistance is reduced. The chemical oxygen demand (COD) removal efficiency was, however, reduced to 64% (compared with 79%). A two-stage system was subsequently run for fuller wastewater treatment and increased power production. The results indicate that a two-stage MFC-CW can increase the normalized energy recovery and improve removal efficiencies of COD, total nitrogen, NH4⁺, total phosphorus and reactive phosphorus to 93 ± 1.7%, 85 ± 5.2%, 90 ± 5.4%, 98 ± 5.3% and 99 ± 2.9%, respectively.

Fate of water treatment residual : an entire profile of Ireland regarding beneficial reuse

Ireland’s water treatment residual (WTR) production rate and reuse situation was investigated to complement the novel research on WTR reuse development in University College Dublin, Ireland. The resulting GIS maps reveal the state of WTR production, disposal and beneficial reuse throughout the country. The total WTR production in Ireland is 15,679 tonnes of dry solids per annum with over 90% of WTR being aluminium‐salt‐coagulated WTR. Only 8% of WTR is recycled or reused via composting, land‐spreading, cement manufacturing, constructed wetlands and quarry remediation. The authors recommend that there be further attempts to use WTR in constructed wetlands and cement manufacturing in Ireland.

Constructed wetland integrated microbial fuel cell system: looking back, moving forward

In the last 10 years, the microbial fuel cell (MFC) has been extensively studied worldwide to extract energy from wastewater via electricity generation. More recently, a merged technique of embedding MFC into a constructed wetland (CW) has been developed and appears to be increasingly investigated. The driving force to integrate these two technologies lies in the fact that CWs naturally possess a redox gradient (depending on flow direction and wetland depth), which is required by MFCs as anaerobic anode and aerobic cathode chambers. No doubt, the integration of MFC with a CW will upgrade the CW to allow it to be used for wastewater treatment and, simultaneously, electricity generation, making CWs more sustainable and environmentally friendly. Currently, published work shows that India, China, Ireland, Spain, Germany and Malaysia are involved in the development of this technology although it is in its infant stage and many technical issues are faced on system configuration, operation and maximisation of electricity production. This paper aims to provide an updated review and analysis of the CW-MFC development. Focuses are placed on the experience gained so far from different researchers in the literature and further research directions and proposals are discussed in great detail.

Water at the Centre of Environmental Issues – Research at the UCD Dooge Centre for Water Resources Research

Since 1988, the UCD Dooge Centre for Water Resources Research has been conducting research in a wide range of water topics including hydraulics, hydrology, coastal dynamics and wastewater with an emphasis on multi-disciplinary collaboration. This paper presents an overview of this research, both past and present, and provides an outlook to the future research directions of the Centre.