New DNA analysis method helps optimise biological phosphate removal

Royal HaskoningDHV and KWR have developed, within the Smart Water Systems theme of TKI Water Technology, a quantitative DNA method (qPCR method), which enables the identification and quantification of bacteria that are able to absorb phosphate from wastewater. The new analysis method allows for better monitoring and further optimisation of biological phosphate removal from wastewater, so that the discharged wastewater contains less phosphate.

The removal of nutrients such as phosphates and nitrates is a key part of wastewater treatment. The discharge of treated nutrient-rich wastewater into the ecosystem can lead to a significant growth of certain species, such as algae, and to a reduction in biodiversity. Wastewater treatment companies are therefore interested in achieving extensive and stable nutrient removal. Biological phosphate removal offers an important aid in this regard: a group of bacteria in the activated sludge remove and store the phosphate from the water so that it remains behind in the sludge. These are the so-called Phosphate Accumulating Organisms (PAOs). However, activated sludge also contains competing bacteria, which have the same metabolism but do not absorb phosphate: the Glycogen Accumulating Organisms (GAOs). Good biological phosphate removal requires the presence of many more PAOs than GAOs. The monitoring and optimisation of the biological phosphate removal process therefore require information about the identity and quantity of the PAOs and GAOs present. The chemical analyses and sludge activity tests currently employed in wastewater treatment provide too little of this information.

Identity as well as quantity

KWR and Royal HaskoningDHV have studied the possibility of obtaining information about the nature and quantity of the PAOs and GAOs present using quantitative DNA techniques (qPCR). To this end, drawing on the literature, the most frequently occurring PAOs and GAOs were identified, after which specific DNA sequences were identified that could possibly be used to demonstrate the presence of these bacteria with qPCR tests. Using these particular primers and probes, qPCR tests were developed to specifically demonstrate the presence of the DNA of PAO and GAO bacteria and to generate calibration curves to determine their quantities. Analyses on test samples from different wastewater treatment plants show that the qPCR tests developed can be used to obtain a picture in a short period of time of the biological phosphate removal in treatment processes. The technologists, on the basis of this information, can optimise their process.

More information

Download the report (in Dutch) on the TKI Water Technology website or contact (Royal HaskoningDHV) or (KWR). This project is part of TKI Water Technology’s Hydrogenomics cluster, which involves the joint development of projects that make use of generic, DNA- and eDNA-based analysis techniques and pattern recognition. The applications focus on drinking water production and distribution as well as surface water quality monitoring (among others, within the framework of the EU’s Bathing Water Directive, Water Framework Directive and Natura 2000). For more information about this cluster contact (KWR).

Nieuwe DNA-analysemethode helpt biologische fosfaatverwijdering te optimaliseren