Is Treated Wastewater Safe for Reuse? - Liquid Chromatography Investigates

Water is a finite resource. This means that we should take care of our water supplies and waste as little water as is possible. It also means that we should reuse water after treating it to remove any potentially harmful compounds. And this introduces us to a world many of us would prefer to ignore - sewage.

In England and Wales there are over 7000 sewage treatment works with around 98% of households connected to the system delivering clean drinking water and clean rivers. But it can be quite a challenge delivering clean water - and the challenge is not just from normal waste. A paper published in the journal Environment International highlights the quantity of antibiotics that can be present in treated wastewater that is then used on the food grown on farms.

Reusing the wastewater

Wastewater reuse is an essential component of the global water supply. Water use is increasing as the world’s population increases and climate change affects where and when our water reserves are refilled. It is estimated that 25% of the world’s population are already in regions where water demand exceeds water supply. So, wastewater treatment of urban wastewater is considered a viable option to help in a water management strategy.

Water reuse has many benefits, but the water has to be clean and safe to use. There have been major improvements in water treatment for the safe removal of solid matter and nutrients. And more is understood now about the importance of chemical and biological oxygen demand for treated wastewater. But there are still concerns about treated wastewater and the presence of contaminants of emerging concern (CEC) - chemical and biological contaminants including pharmaceuticals and even antibiotic resistant genes.

Chromatography separates the waste

In the paper - Evaluation of chemical and biological contaminants of emerging concern in treated wastewater intended for agricultural reuse - researchers from various European countries used passive sampling to sample wastewater from wastewater treatment plants in Cyprus. The treatment plants used sedimentation and membrane bioreactors to treat the water.

They then analysed the samples using solid phase extraction and a combination of ultra high-performance liquid chromatography with mass spectrometry. Chromatography is an ideal solution when analysing water samples as discussed in the article, Elimination of the Sample Solvent Effect when Analysing Water Solutions of Basic Peptides by HILIC.

The researchers found that the treated samples contained antibiotic resistant genes and contaminants of emerging concern. The researchers state that the compounds detected are highlighting potential chemical and biological hazards related to wastewater reuse practices. However, the risk of some of the compounds detected is not yet known. They do report that the method developed and sampling techniques used suggest a way forward for ensuring the treated wastewater can be analysed and passed as safe to use in future.