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Utilising periphytic algae as nutrient removal systems for the treatment of diffuse nutrient pollution in waterways

Sutherland, Donna L., Craggs, Rupert J.
Algal research 2017 v.25 pp. 496-506
algae, biofuels, biomass, climatic factors, cost effectiveness, freshwater, harvesting, land use, microorganisms, nitrogen, nutrients, periphyton, phosphorus, photosynthesis, pollution control, pollution load, sediments, surface water, waterways, wetlands
Contaminant loads derived from land-use intensification, such as nutrients, sediment and microorganisms, are a particular concern for vulnerable and sensitive waterbodies. While a number of diffuse nutrient pollution mitigation systems are currently available, these are not yet widely applied or where they have been, some residual contaminants are still lost from the land. Adoption of, efficient mitigation systems that can be applied to a range of land types and environments, operate along pollution gradients and are cost-effective at a range of scales are therefore vital to meet the strategic objectives of freshwater management, whilst supporting economic growth.Periphyton nutrient removal systems (PNRS) are a biological-based mitigation system that is capable of treating diffuse nutrient pollution in waterways, resulting in reduced nutrient loads to downstream waterways. During photosynthesis and growth, the algal component of the periphyton matrix quickly assimilates dissolved nitrogen and phosphorus from the overlying water into its biomass. Nutrient assimilation coupled with periodic harvesting of the algal biomass to permanently remove these nutrients from the waterway provides an opportunity to exploit periphyton for diffuse nutrient pollution mitigation.Current research indicates that such systems would have half the land requirements of a wetland treatment system for the same nitrogen removal rate as well as less capital costs and require only weeks to become fully established. PNRS have the added benefit of resource recovery for beneficial re-use for food, fertiliser, or biofuel. Further research is needed on the optimisation of PNRS design and operation to enhance performance. This research would help inform the adaption of PNRS to suit local climatic conditions, nutrient pollution type and level and treatment objectives.