“Our AnMBR tech reduces energy consumption and volume of sludge biomass, while generating energy”
The King Abdullah University of Science and Technology (KAUST) aspires to be a leading center for scientific and technological education and research. Its Water, Desalination, and Reuse Center aims to revolutionize the water cycle by reducing energy and chemical use, minimizing leaks and evaporation, and maximizing the recovery of water, energy, nutrients, and minerals.
Since joining Saudi Arabia’s prominent King Abdullah University of Science and Technology (KAUST) in 2012, Professor Peiying Hong and her research team have been focused on developing energy-efficient wastewater treatment methods that produce high-quality effluent suitable for reuse. Their efforts have led to a decentralized system capable of treating sewage entirely off-grid.
In July 2022, this innovative decentralized process was implemented in a pilot treatment plant in Jeddah, Saudi Arabia. Operated in collaboration with the Saudi Authority for Industrial Cities and Technology Zones (MODON) and funded by KAUST, this plant treats 50,000 litres of wastewater daily without relying on grid energy.
Smart Water Magazine had the chance to sit down with Professor Hong to discuss her energy-efficient wastewater treatment technology, the success of the pilot project, the future steps and the meaning of this sustainable sewage treatment solution for Saudia Arabia and the rest of the world.
Can you tell me briefly about your career path and current role at King Abdullah University of Science and Technology (KAUST)?
I did my PhD at the National University of Singapore (NUS), specializing in applied environmental microbiology in Environmental Science and Engineering. During my PhD, I was developing molecular methods to examine the microbial communities in stool samples to relate to the origin of contamination and the health status of the host. I then did my postdoctoral training at the University of Illinois at Urbana Champaign, and worked on a United States Department of Agriculture funded project that aims to elucidate how antibiotics use in livestock production farms can affect the extent of antimicrobial resistance threats in the manure, groundwater, soil and air. Through these projects, I learnt the immense amount of information one can gain by looking at the microbial communities in the various waste streams.
We are looking into a suitable pretreatment step to do a partial treatment of complex industrial wastewater prior to the AnMBR technology
When I arrived at KAUST in Saudi Arabia as an Assistant Professor, I learnt that wastewater can be a very important water source to address water scarcity in this hyperarid country, and yet water reuse remains taboo. I wanted to understand the emerging microbial contaminants that are present in the wastewater, and to utilize that knowledge to develop good intervention measures in the form of engineered wastewater treatment systems and best management practices. This is done to promote higher acceptance towards water reuse through a science-based approach. Over the past 12 years, we have been working towards increasing our knowledge in this area and developing solutions to derive safe and sustainably sourced reclaimed water.
Can you explain how anaerobic membrane bioreactor (AnMBR) technology differs from traditional aerobic wastewater treatment methods, and what advantages it offers?
The anaerobic membrane bioreactor utilizes a completely different suite of microorganisms that thrive in the absence of oxygen, unlike that in an aerobic wastewater treatment plant that requires a sufficient amount of dissolved oxygen to be provided. In the absence of oxygen, the anaerobic microorganisms convert the organic carbon in wastewater to volatile fatty acids and methane. Methane can be combusted into an energy source. This is in contrast to aerobic microorganisms that utilize the organic carbon in wastewater to support microbial cell growth. Based on these differences, the advantages of our AnMBR technology are decreased energy consumption (because of the elimination of aeration), reduced volume of sludge biomass and the ability to generate energy. Coupling the anaerobic digester with membrane filtration can also improve the effluent quality.
What were the key challenges you encountered whilst implementing the AnMBR technology in the pilot program with MODON in Jeddah, and how were they addressed?
We initiated the program when COVID-19 first hit and there was a significant challenge in initiating the logistics required to ship the reactors from overseas to Saudi Arabia. We also faced a delay in getting the civil construction work done in time. We had to communicate constantly with the different stakeholders and oversee the completion of these tasks.
Once the AnMBR technology was commissioned, the challenge lay in ensuring the AnMBR technology remained robust despite variability in real wastewater quality (e.g. highly variable pH and chemicals). In addition, there were some unforeseen circumstances such as heavy rainfall which flooded the entire site and did not permit our manpower to operate the system in person. Fortunately, despite these challenges, we have shown over the past two years that our treatment plant can operate in a very robust manner and continue to purify the wastewater to meet our imposed suite of key performance indicators.
What are some specific opportunities and challenges you foresee in scaling up the AnMBR technology into broader implementation across different regions and industries?
Our technology can facilitate efficient capture of all wastewaters that are currently not connected to centralized wastewater treatment plants
In different regions, the local climate may be different from that in Saudi Arabia. We currently operate our AnMBR technology in a hot climate, which favours anaerobic fermentation. In places with temperate climates, anaerobic fermentation may result in a higher percentage of methane dissolved in the aqueous phase and contribute towards greenhouse gas emissions when the reclaimed water is reused. We are looking into technological solutions to reduce dissolved methane in the reclaimed water to improve the overall life cycle of the AnMBR technology.
As the AnMBR technology continues to scale up and be deployed to different industries, it will be challenged with very different wastewater quality than that we have tested. For example, industries wastewater that are receiving discharge from petroleum refineries would contain high concentrations of sulphate and hydrocarbons, which can significantly challenge the anaerobic fermentation process. We are currently looking into a suitable pretreatment step to do a partial treatment of complex industrial wastewater prior to the AnMBR technology.
In what ways does the AnMBR technology contribute to the broader goals of Vision 2030 in Saudi Arabia, particularly in terms of water reuse and sustainability?
In the Saudi Vision 2030, the goal is to achieve 100% sewage capture and reuse. Nevertheless, achieving 100% sewage capture can be challenging if Saudi Arabia only relies on a centralized wastewater capture and treatment model. This is because a centralized model would require extensive excavation to lay out the sewage network, which can create significant disturbances to the existing communities. In addition, populations living in peri-urban/rural communities are often overlooked when it comes to sanitation infrastructure planning. This is because of various reasons such as long proximity to the existing centralized wastewater treatment plant, and low generated sewage volume over a scattered population density, all of which necessitate substantial investments to bring the existing sanitation solutions to these populations. Our technology can facilitate efficient capture of all wastewater that are currently not connected to centralized wastewater treatment plants, purify them, and immediately reuse the purified water in nearby vicinities.
Compared to existing aerobic-based solutions which require mechanical aeration, our anaerobic-based solution eliminates the need for aeration
In addition, Saudi Vision 2030 aims to move towards more sustainable practices that do not emit a large carbon footprint. Compared to existing aerobic-based solutions which require mechanical aeration, our anaerobic-based solution eliminates the need for aeration. Thus, our solution generates only 0.3 kg equivalent of carbon dioxide per 1000 L of wastewater purified, which is half of the 0.6 kg equivalent of carbon dioxide (greenhouse gas) for every 1000 L of wastewater purified by the conventional aerobic-based wastewater purification solution.
Lastly, since July 2022, our system has successfully demonstrated that we can generate an average of 1.5 kWh of electrical energy for every 1000 litres of wastewater treated. In addition to this, we harvest approximately 410 kWh of solar energy daily and store it onsite in battery systems, enabling our solution to operate continuously using only clean renewable energy.
Can you discuss the potential environmental benefits of implementing the AnMBR technology compared to traditional wastewater treatment methods?
In addition to what was mentioned in the previous response, our solution also generates very little solid waste sludge. For example, over a period of 30 weeks of operation, our solution did not produce any solid waste. This is in contrast to the aerobic-based wastewater purification solution that generates on average 0.6 L of solid waste per 1000 L of wastewater purified. The solid waste generated from the wastewater treatment process usually accumulates high concentrations of pharmaceutical compounds, estrogens, heavy metals and antibiotic-resistance genes. Our solution therefore positively impacts the environment by minimizing the amount of hazardous solid waste that needs to be handled and disposed of.
Our system has demonstrated that we can generate an average of 1.5 kWh of electrical energy for every 1000 litres of wastewater treated
Our solution currently generates 50,000 L of high-quality reclaimed water which contains about 50 mg/L of ammonium, which can be used to support the growth of nutritious food crops (e.g. lettuce). Every 1 kg of marketable yield of lettuce requires about 20 L of water over a harvest cycle of 60 days. As our current solution produces 50,000 L of water per day, this means that 150 tons of lettuce can be made from our reclaimed water for each harvest cycle.
Could you discuss the economic feasibility of the AnMBR technology, including factors such as initial investment costs, operational expenses, and potential cost savings compared to conventional treatment methods?
We published a perspective recently to discuss the economic feasibility. In this paper, we showed that AnMBR technology costs about 855 USD per m3 for the initial investment costs. This is about 18% cheaper than the aerobic membrane bioreactor technology. The AnMBR technology’s operation cost is 0.067 USD/m3 (including energy consumption, membrane replacement, and chemical consumption), which is lower than AeMBR (0.100 USD/m3).
Looking ahead, what are the next steps in your research, and how do you plan to continue collaborating with industry partners and stakeholders to advance the field of wastewater treatment?
We are currently demonstrating our technology at a treatment capacity of 50 m3 per day. However, we learnt from our conversations with the relevant stakeholders that in most instances, they are generating wastewater that is at least 1000 m3 per day. We will therefore need more investment to scale up our technology to about 600 m3 per day, and demonstrate that the technology can work efficiently at that scale to treat different types of wastewater. We are in the midst of conversations to solicit funding from industry partners, investors and other stakeholders. Once successfully demonstrated, this will allow us to scale up accordingly by installing multiple modular units, with each module providing 600 m3 treatment capacity.