Quality assurance, Biodegradation and tools for its assessment

This session will include the speakers: Andrea Aldas-Vargas (Environmental Technology, Wageningen University & Research), Rita H.R. Branco (Sub-department of Environmental Technology, Wageningen University & Research and Wetsus, European Centre of Excellence for Sustainable Water Technology), and Nienke Koeman (KWR)

Take a look at the abstracts below:

Biostimulation as a tool to assess pesticide biodegradation capacity of microorganisms in groundwater

Presenting author: Andrea Aldas-Vargas

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Groundwater is the main source for drinking water production globally. Groundwater unfortunately can contain micropollutants (MPs) such as pesticides and/or pesticide metabolites. A recent study examining drinking water-abstraction areas covering groundwater and surface water bodies in the Netherlands found pesticides and/or metabolites in 150 out of 226 samples (Sjerps, Kooij, van Loon, & Van Wezel, 2019). Biological remediation of MPs in groundwater requires an understanding of natural biodegradation capacity and the conditions required to stimulate biodegradation activity. Natural intrinsic biodegradation processes in groundwater can be limited due to (1) supply of electron acceptors, (2) growth substrate, (3) absence of degrading. To assess pesticide biodegradation capacity of field microorganisms, groundwater samples were taken from two monitoring wells located at the north-east of The Netherlands, at five different depths ranging from 13 to 54 m below ground level. Biodegradation of the MPs BAM, MCPP and 2,4-D was assessed in mesocosms with groundwater samples, either without amendment, or with amendment with electron acceptor (nitrate or oxygen) and/or carbon substrate (dissolved organic carbon (DOC). Oxygen+DOC was the most successful amendment resulting in complete biodegradation of 2,4-D in all mesocosms after 42 days. DOC was most likely used as a growth substrate that enhanced co-metabolic 2,4-D degradation with oxygen as electron acceptor. Different biodegradation rates were observed per groundwater sample. Overall, microorganisms from the shallow aquifer had faster biodegradation rates than those from the deep aquifer. Higher microbial activity was also observed in terms of CO2 production in the mesocosms with shallow groundwater. Longer exposition time to both DOC and MPs could have resulted in microbial adaptation and better biodegradation in shallow samples. Understanding field biodegradation capacity is a key step towards developing further bioremediation-based technologies. Our results show that biostimulation has real potential as a technology for remediating MPs in aquifers in order to ensure safe drinking production.

Effect of different types of dissolved organic matter and redox conditions on micropollutant biodegradation by aquifer microbial community

Presenting author: Rita H.R. Branco

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Groundwater, the largest body of freshwater in the European Union (EU), supplies drinking water to about 75% of its residents. Nevertheless, micropollutants, such as pesticides, pharmaceuticals and industrial substances, are detected in European groundwater above the concentration limits set by the EU (0.1 μg/L for individual pesticides and 0.5 μg/L for total pesticides). Removal of micropollutants at the source of contamination is difficult given its diffuse and diverse nature. Micropollutants can enter the water cycle either from point sources, as wastewater treatment plants (WWTPs), or diffuse sources, such as landfills and agricultural fields treated with pesticide or manure. To ensure safe drinking water, drinking water production relies on energy-intensive adsorption or advanced oxidation technologies.

Biodegradation, the major process for natural attenuation of xenobiotics in the environment, could be a cost-effective and sustainable solution. However, groundwater is often oligotrophic and many aquifers are anaerobic, which limits in situ microbial activity and thus micropollutant biodegradation. Recent studies have shown that amendment with dissolved organic matter (DOM) can enhance biodegradation. Therefore, a DOM-based in situ bioremediation technology could be developed to remove micropollutants in groundwater (Figure 1). However, little is known about the mechanism by which DOM supports micropollutants biodegradation.

The aim of this study is to understand how DOM amendment can be used to enhance in situ micropollutant biodegradation in groundwater. Therefore, we investigated the biodegradation of micropollutants frequently found in groundwater by an aquifer microbial culture under two redox conditions, i.e. aerobic and nitrate reducing. The effect of DOM sources with different biodegradability, such as acetate, dextran and humic substances, on micropollutant degradation was evaluated. By monitoring micropollutant transformation, DOM and electron acceptor consumption, as well as microbial community composition and the presence of functional genes for micropollutant degradation, we aim at understanding how different DOM types can enhance micropollutant biodegradation. This is thus a first step towards developing an in situ micropollutant bioremediation technology.

Acceptance and quality assurance of safe irrigation water from municipal wastewater 

Presenting author: Nienke Koeman

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The irrigation water supply for the greenhouse horticulture sector is under increasing pressure, which is exacerbated by the effects of climate change. Hence, there is a need for alternative water sources for irrigation. In addition, a more general goal is to make water use more circular and to investigate the opportunities for reuse of wastewater in more depth. This includes a situation in which treated wastewater is reused as much as possible, to allow the most sustainable use. This comes together by using treated wastewater as an alternative irrigation source in greenhouse horticulture.  

Previous research has shown the possibility of growing tomatoes with effluent that has been treated to be used as irrigation water, without loss of crop quality and yield. However, to further ensure minimal safety risks for people and plants, quality assurance of irrigation water is required. It is expected that this will also support the acceptance of treated effluent as a source for irrigation throughout the chain from grower to consumer. This project carries out a risk inventory and develops a monitoring plan, supported by the relevant stakeholders, that enables the next steps in greenhouse horticulture. To this end, a guideline is developed together with stakeholders in the supply chain, growers, water companies, traders, etc., that describes the conditions that treated effluent (but also wastewater from other sources) must meet to be used as irrigation water. These conditions are both of technological as well as of legislative nature. The continuous measurement of chemical markers, the use of sensors, non-invasive measurement techniques, and decision support systems can be part of the monitoring strategy. This way, more clarity about the assurance of the quality of the water is developed to propose effluent as a technologically feasible – but most of all safe – alternative irrigation source.  

In this presentation, an overview of the prevailing legislation and regulations for the use of effluent in greenhouse horticulture is given. This overview includes requirements for water quality parameters to guide tailor-made reprocessing of the effluent for safe cultivation with recycled irrigation water. The prevailing legislations require the quality to be dependent on the risk for (human) health. Therefore, a risk inventory and a framework for a monitoring plan are also made, including smart sensors and data processing for the safe application of irrigation water. By involving the entire chain in stakeholder meetings, important steps are made towards a broad acceptance of the use of effluent as a safe source of irrigation water; from grower to consumer. 

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