By Dr Farrukh Ahmad, Dr Jorge Rodriguez and Dr Andreas Henschel
With little or no freshwater, the UAE relies heavily on costly, energy- intensive desalination plants. Treating wastewater is much cheaper – if only we could make more use of it.
According to the Statistics Centre Abu Dhabi, in 2012 treated wastewater met less than 10% of Abu Dhabi city’s total water demand.
Desalinated water and groundwater met 79% and 12% of the total water demand, respectively.
Treated wastewater is currently used only for irrigation and landscaping. If we could put it to other uses, we could make a big dent in our carbon and energy expenditure.
But for applications beyond irrigation, science must first address important questions about water for treatment and reuse. What happens to micropollutants and pathogens in the wastewater treatment process?
What happens to any residual micropollutants and pathogens present in recycled water when it is reused? Or to put it more simply, do we remove the harmful stuff, and how harmful is the stuff we don’t remove?
Micropollutants consist of natural and synthetic chemicals, from hormones to pharmaceuticals and flame-retardants.
They are typically organic compounds, found at low concentrations in the municipal waste stream as a result of their large-scale production and widespread use in commercial and consumer products.
They affect both human and other living things, disrupting endocrine – hormonal – systems, killing cells, and causing increased antibiotic resistance.
One uncertainty is where the large number of micropollutants present in wastewater end up.
These compounds tend to persist in treated wastewater because conventional treatment processes, like activated sludge treatment and membrane bioreactors, do not target their removal.
In order to address these concerns, we at Masdar Institute are interested in using a comprehensive and multi-disciplinary computational, experimental, and field-scale approach at all points along the wastewater generation, treatment, and end-use process train to help allow more water to be reused safely.
Analysing micropollutants requires sophisticated instruments and techniques, such as gas and liquid chromatography coupled with mass spectrometry, which most water utilities are not equipped for.
Monitoring pathogens and other biological agents is tricky, too. All water, even tap water and bottled drinking water, contains complex microbial communities that are, for the most part harmless to humans.
Unlike chemical contaminants, microbes can multiply in the treatment system – so counting the microbes in one part of the system doesn’t necessarily tell you how many there are somewhere else.
And while some microbes are potentially pathogenic, many others are entirely benign. So simply counting them – as is the conventional practice – doesn’t tell you if there’s actually anything to worry about.
For these reasons, conventional microbiological methods are grossly inadequate for monitoring presence and levels of pathogens, especially in warm and hot climates.
Modern molecular biological techniques, such as polymerase chain reaction (PCR) and high-throughput or metagenomic DNA sequencing, can provide cost-effective, detailed analysis of the microbes present, including pathogens.
These techniques, coupled with quantitative chemical and microbial risk assessment, offer a scientifically robust way of assessing any health risk from disease vectors in treated wastewater.
This, in turn, would allow the UAE to use treated wastewater for a wider variety of applications – which would reduce the UAE’s carbon footprint and energy demand, while enhancing food and water security.
Dr Farrukh Ahmad is associate professor of water and environmental engineering, Dr Jorge Rodríguez is assistant professor of water and environmental engineering, and Dr Andreas Henschel is assistant professor of computing and information science, all at the Masdar Institute of Science and Technology.