A pioneering collaborative research project between Wessex Water and the University of Bath is investigating using algae as a natural and sustainable way to treat wastewater.
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A pioneering collaborative research project between Wessex Water and the University of Bath is investigating using algae as a natural and sustainable way to treat wastewater.
The water company has teamed up with the university's Water Innovation and Research Centre (WIRC @ Bath) to create algae ponds to remove nutrients from wastewater, while also generating a valuable by-product.
The team, led by Dr Tom Arnot in the university's department of chemical engineering and Professor Rod Scott in the department of biology and biochemistry, is investigating utilising algae ponds to treat wastewater and reduce levels of phosphorus.
Managing phosphorus is major challenge for UK water companies
Phosphorus is a non-renewable resource present in human waste and used in detergents, agricultural fertilisers and cleaning products. It is also a water pollutant which can cause both environmental and economic damage.
Removing phosphorus from water bodies has become an increasingly key concern for the UK's water utility companies, with pressure from the Environment Agency to find new solutions due to the Water Framework Directive.
When phosphorus levels become too high in the environment, eutrophication can occur. High phosphorus causes an increase in algal blooms and other aquatic plants, which leads to a depletion in oxygen levels within rivers and streams as well as the potential release of toxins from the algae.The phenomenon results in a significant loss of plant, insect and fish species and an overall less healthy watercourse.
A new approach for the UK
The current trial aims to use a 'managed eutrophication' approach to address the problem. Rather than allowing wastewater to release nutrients which encourages algae to grow in the watercourse and cause damage, algae are grown at the sewage treatment works in a managed way and removed before the water enters the river.
This results in "polished" wastewater that can then be released into the river, plus algae biomass which can be recovered and used as a resource. To achieve this, a pilot High-Rate Algal Pond (HRAP) system has been installed at Wessex Water’s sewage treatment works in Beckington, Somerset.
The system at Beckington consists of two shallow ponds with a total functional area of 60m2 and capacity of 18,000 litres, where wastewater is continuously circulated by paddlewheels.
The HRAPs are seeded with the desired species of algae and fed with final wastewater effluent, which would otherwise be released into the environment. Within each pond, algae use nutrients in the wastewater, sunlight and carbon dioxide to grow, thereby reducing overall nutrient levels including phosphorous.
Nutrient-rich algae can be used in bioplastics, biofuels & agricultural fertiliser
A proportion of the water and algae mixture is then moved to a settling tank and separated daily, while fresh effluent is added to top up the ponds. This results in “polished” wastewater with lower levels of harmful nutrients which can be returned to the environment, and algae rich in nutrients that can be used for various purposes such as bioplastics, biofuel and agricultural fertiliser. By using this system algae can be grown in a managed way and removed before wastewater reaches the river.
This is the first time such a potentially sustainable solution is adapted for phosphorus removal and deployed at a pilot scale in the UK.
The trial is treating approximately 3,000 litres of wastewater per day, while removing 80-96 per cent of the phosphorus present. It also aims to assess the performance, costs, reliability and practicality of this sustainable technology in order to determine whether it can be a suitable solution for phosphorus removal in realistic conditions.
National programme to investigate new phosphorous removal technologies
Currently, traditional methods for treating sewage water use chemical dosing with iron salts to bind phosphorus. However, new technologies are needed to meet tightening environmental regulations for a variety of STW types and sizes while avoiding a significant increase in consumer’s water bills.
The project is one of a number of trials being undertaken by all water and sewage companies across England and Wales as part of a national collaborative programme to investigate new phosphorus removal technologies.
At the end of the trials, the water and sewage companies will share the results of their trials with each other and the Environment Agency in an attempt to identify the best solutions to removing phosphorus.