Advanced Landfill Waste Alleviation and Resource Mining Strategies
Lead Research Organisation:
Imperial College London
Department Name: Chemical Engineering
Abstract
Landfilling is one of the cheapest options for municipal solid waste management, which has been in practice for centuries. However, generation of municipal landfill leachate (MLL) with concentrated hazardous pollutants is the biggest downside of this process. MLL treatment is challenging with conventional treatment technologies due to its intrinsic toxicity and to date, none of the technology can provide a single-stage carbon and nutrient removal at a low carbon footprint and energy expenditure. For instance, in Europe, MLL is mostly managed in urban wastewater treatment plants (UWTPs) using combined pre-treatment and energy-intensive post-biological strategies yet many small UWTPs fail to comply with the discharge limit of ammonia and emerging pollutants. This is emphasizing an urgent need to develop a new decentralized single-stage solution. In ALARMS, we propose to develop an integrated purple non-sulfur bacteria (PNSB)-based biotechnology for onsite MLL treatment and resource recovery at low-carbon footprint. PNSB own versatile metabolic pathways, enabling them to participate in the natural nutrients fixation cycle using photosynthesis process. Thus, most of the studies utilized PNSB as a superior heterotroph to treat a wide range of wastewater. To date, a few recent research uncovered unlimited potential of PNSB as cathode respiring bacteria to derive biofuels (e.g., H2) at high conversion efficiency from synthetic media, which is yet to be explored for real wastewater treatment, especially for MLL. Here, we will isolate mixed PNSB from natural sources and electrochemically activate it to induce a desired metabolic response and utilize it as both autotroph and heterotroph to efficiently remove/recover nutrients and organics in a single stage from MLL using novel electrochemical photobioreactors. This project is interdisciplinary combining material science, biotechnology, electrochemistry, and metabolic engineering, and is aligned with the EU's 2050 goal of zero carbon footprint.
Organisations
Publications
Noori M
(2025)
Per- and polyfluoroalkyl substances (PFAS): An emerging environmental challenge and (microbial)bioelectrochemical treatment strategies
in Current Opinion in Environmental Science & Health
| Description | 1. The study title "Enhancing Photocurrent Production in Synechocystis sp. PCC 6803 for high-rate hydrogen production in dual-chamber photoelectrochemical systems" showcases notable progress in employing bioelectrochemical systems for renewable energy generation. Detailed findings are outlined in the following paragraphs, with key points emphasised: Improved Photocurrent and Hydrogen Generation: The research introduced a novel strategy to significantly enhance photocurrent generation by applying a 1.0 V potential stress at the anode in a dual-chamber photoelectrochemical system (PES). This method elevated the average photocurrent density to 2.1 mA/cm², compared to lower densities in PES without this applied potential. Utilising the enhanced photocurrent, the system produced biohydrogen at an impressive rate of 0.154 m³/m²·d at the cathode. With around 90% energy efficiency, this highlights the PES's ability to transform biological processes into usable energy. Moreover, the potential stress not only improved photocurrent and hydrogen generation but also significantly increased microbial activity. This enhancement was evident in the excellent production of single-cell protein, with production rates reaching 1.52 mg/L·h under potential stress conditions, surpassing the 1.12 mg/L·h observed in systems without bias and the 1 mg/L·h recorded in control experiments. The study underscores the dual benefits of the employed technology-boosting energy production while simultaneously elevating microbial productivity, which is crucial for sustainable biotechnological applications. Research indicates that strategies designed to boost photocurrent generation and biohydrogen production have significant potential in environmental biotechnology and chemical manufacturing. This is especially pertinent for processes that exploit the natural abilities of electroactive cyanobacteria, particularly Synechocystis sp. PCC 6803. 2. The study title "Isolation of Robust Phototrophic Purple Bacteria and Their Application in Treating Leachate within Bioelectrochemical Systems under Various Operating Conditions for Optimization" explores the role of purple bacteria in bioelectrochemical systems (BES) for wastewater treatment and the synthesis of biodegradable plastics. This study offers important insights into optimising these systems for real-world applications, particularly in ammonia and nitrate removal and the production of microbial bioplastics. Below is a comprehensive analysis of the essential findings: Prevalence of Hydrogenophaga species kbb11 in the isolated purple bacteria consortium: We isolated purple bacteria from landfill sludge using selective enrichment methods at the infrared light spectrum (800 to 900 nm). The RT-PCR tests identify Hydrogenophaga sp. kbb11 as the dominant microbial species, indicating its robust nature and adaptability in bioelectrochemical settings. This bacterium's prevalence suggests it has promising capabilities for applications requiring resilience to high concentrations of ammonia and nitrate, typical of many industrial wastewaters. Studies on efficient Ammonia and Nitrate Removal: Ammonia and nitrate removal was assessed in single-chamber bioelectrochemical reactors operated under varying voltage conditions (0.4 V, 0.8 V, and 1.2 V). The reactors equipped with electrodes, referred to as BES, displayed superior removal efficiencies compared to the control setups without electrodes. Notably, the system subjected to 0.8 V (BES-0.8) exhibited the most effective nitrogen removal rates (67.2 mg-N/L·d), indicating that this voltage optimally supports the metabolic processes crucial for efficient contaminant degradation. Optimisation of Ammonia to Nitrate Ratios: The BES-0.8 system was further tested across various ammonia to nitrate ratios, ranging from 2.5:1 to 20:1. An optimal ratio of 3.33:1 (1000 mg/L NH4+ to 300 mg/L NO3-) was identified as the most effective for achieving a nitrogen removal rate of 68.5 mg-N/L·d, striking a balance between microbial needs for nutrient removal and system stability. This finding is vital for designing treatment protocols that maximise efficiency while minimising operational costs. Biomass Growth and Microbial Concentration: Analysis of biomass growth under the optimal NH4+/NO3- ratio (3.33:1) in BES-0.8 revealed that higher initial microbial concentrations (1500 mg/L and 2000 mg/L MLVSS) resulted in more robust biomass development, achieving a biomass growth of 2.84 gdw/L (@0.284 gdw/L.d). This correlation underscores the importance of inoculum size in scaling up bioelectrochemical systems for commercial applications, impacting the overall treatment efficiency and stability of the reactor. Production and Analysis of Microbial Bioplastics: We conducted further tests on bioresource recovery as polyhydroxy butyrate (PHB) derived from mixed purple bacteria biomass. Under optimised conditions, we achieved a PHB recovery of 349 mg/gdw, representing about 35% of the cell biomass. Consequently, the maximum PHB yield attained was 1 g/L in BES-0.8, operating at a 3.33:1 ratio. We also performed XRD, FTIR, and NMR tests to characterise the bioplastics extracted from the purple bacteria, comparing these results with commercially available products. The analyses demonstrated that the structure and quality of the bioplastics produced by the bacteria were comparable to those of market-available PHB. This research underscores the dual functionality of the microbial treatment system, which effectively treats wastewater while producing valuable biodegradable plastics. It elucidates the diverse applications of purple bacteria in bioelectrochemical systems, presenting a sustainable approach to wastewater treatment and generating economically valuable bioproducts. The findings lay the groundwork for future studies and the development of technologies exploiting microbial capabilities for environmental and industrial purposes. |
| Exploitation Route | 1. Improving Photocurrent Production in Synechocystis sp. PCC 6803 Renewable Energy Sector: Renewable energy companies and startups focusing on bioenergy can adopt the study's methodology to enhance photocurrent production for high-rate hydrogen production. The developed technology can be integrated into existing renewable energy systems to improve the efficiency of biological hydrogen production, a clean and sustainable energy source. Academic and Research Institutions: Researchers can use the findings to explore further the genetic and metabolic pathways of Synechocystis sp. PCC 6803 (soon to publish) that leads to enhanced photocurrent production. This can open up new avenues in microbial bioengineering to optimise other strains for similar or greater efficiencies. Environmental Policy and Sustainability: Governments and environmental agencies can advocate for the utilisation of bioelectrochemical systems to bolster sustainable energy policies. By showcasing high energy efficiency alongside dual benefits-energy production and microbial productivity-these systems can serve as a model for policy frameworks that foster biotechnological solutions to energy requirements. 2. Isolation of Robust Purple Bacteria and Their Application in Treating Leachate Wastewater Treatment Facilities: Utilising robust phototrophic purple bacteria in BES provides a novel approach to treating highly contaminated leachate and other complex wastewaters. Wastewater treatment plants can implement this technology to improve their nitrogen removal processes at a single step, particularly in industrial environments with high ammonia and nitrate concentrations. Bioplastic Manufacturers: The study's success in producing biodegradable plastics at a high rate from microbial bioprocesses provides a pathway for bioplastic manufacturers to explore microbial PHB production as an eco-friendly and sustainable alternative to conventional plastics. Environmental NGOs and Community Projects: Non-governmental organisations focusing on environmental conservation and sustainable development can use these findings to promote community-based projects that integrate waste treatment with bioproduct recovery, fostering local circular economies. Cross-Cutting Impacts Innovation and Collaboration: Both studies highlight the potential for interdisciplinary collaboration, bringing together microbiologists, chemical engineers, and environmental scientists to innovate biotechnological solutions for environmental challenges. Education and Training: Educational institutions can incorporate these case studies into curricula, providing students with insights into practical applications of microbiology and environmental engineering. Scaling and Commercialization: Entrepreneurs and venture capitalists interested in green technologies can consider these systems for scaling and commercialisation, potentially leading to new startups and business models focused on sustainability. Therefore, the outcomes of these studies not only advance scientific understanding and technology development in their respective fields but also offer practical, scalable solutions that can be adopted by industry, academia, and policymakers to address some of today's pressing environmental challenges. This demonstrates a clear path for taking these innovations from the lab to real-world applications, contributing to a more sustainable and resource-efficient future. |
| Sectors | Chemicals Energy Environment Manufacturing including Industrial Biotechology |