Water & Wastewater Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/1094482
24 | APRIL 2019 | WWT | www.wwtonline.co.uk predicted to occur over the next 21 years, reduced algal growth via shading. However, low organic matter additions, predicted to take place over the next four years, stimu- lated algal growth, especially cyanobacteria. It is likely that cyanobacterial blooms will be favoured by climate warming; they represent an increasing threat to water quality, with implications for treatment costs, human health, taste and odour. An understanding of the combined effect of climate warming, nutrient input and high rainfall events on cyanobacteria was the focus of another recent mesocosm experiment. We simulated rainfall events every 12 weeks by adding 1,500 litres of water from a nearby reservoir to each designated mesocosm. Temperature increase and nutrient addition combined did not stimulate cyanobacte- rial growth as much as an- ticipated. In fact, at very high nutrient concentrations, other limiting factors seemed to alter interactions. High rainfall events only had a short-term effect on algal abundance, meaning that water quality recovered quite quickly from the perturbation. Given the growing popular- ity of floatovoltaics - floating solar panels - as a potential renewable energy source, we set up a mesocosm experiment to investigate the effects of such installations upon lake ecosystems. We focused upon changes in the physical prop- erties of the water, tempera- ture and solar radiation, but whole ecosystem implications are yet unknown. The smooth and success- ful running of the mesocosm experiments has proven that the site is a very reliable facil- ity, scalable for both large and small-scale studies. We can set up controlled, replicated, treatments in large ecosystems open to the atmosphere, and the site is easily accessible. CEH staff in Lancaster have years of knowledge and exper- tise on running and managing mesocosm experiments, and The Knowledge Water quality and tanks interpreting the evidence that is generated by them. Potential future water industry applications The mesocosm facility is a highly versatile site and can be used for an array of different applications: from short-term experiments of a few weeks, to long-term experiments over years; from a few mesocosms to the entire facility of 32 mesocosms. If research is aimed at a particular reser- voir, water from the site (if accessible) can be transported to the mesocosms to ensure identical communities. There is the potential to run a suite of different experiments, but two current water industry priorities are ideally-suited to mesocosm research: floatovol- taics and taste and odour. Currently, floatovoltaics are installed at various reservoirs within the country. However, the positive and negative environmental impacts of such installations are not under- stood. Possible water quality effects could be investigated in the mesocosms. Another potential application for mesocosm research could be taste and odour issues, and the key question: what could the industry do to manage cyanobacterial blooms, the main producer of geosmin? Geosmin causes taste and odour problems as it can be detected by end users in very low concentrations. Whatever the chosen focus of a mesocosm experiment might be, results could inform decision making and poten- tially reduce water treatment costs. For more information visit www.ceh.ac.uk