Water recycling to shrink carbon footprint

Leicester, UK - Increased recycling of water that has been contaminated during manufacturing processes would help to significantly reduce industry’s carbon footprint, according to researchers at De Montfort University Leicester (DMU), who claim to have found a way to boost the energy efficiency of a method of recycling industrial wastewater.

According to DMU, the study marks the first time that the efficiency of membrane bioreactor plants has been assessed using computer-modelling techniques. Academics leading the project believe initial results show plants can be made between 10% to 15% cheaper to operate.

Industrial wastewater is water which has been contaminated while being used for a specific purpose, for example in the brewing process during the manufacture of alcohol, or in the cleaning of ingredients used for food products. Contaminants typically include biological materials or industrial by-products and the wastewater is usually thrown away.

Parneet Paul, a senior research fellow within DMU’s Process Control - Water Software Systems (PC-WSS) and the project coordinator, said: “If the water is recycled, it can be reused, thereby reducing a company’s water utility costs and helping to reduce their energy footprint.

If this wastewater can be fully recovered in an efficient manner it not only has cost implications for industry as a whole, but could also be a way for industry to meet its targets to reduce its green house gas emissions, believes Paul - a chartered civil/chemical engineer and a chartered environmentalist with experience of the water sector both in the UK and overseas.

“Many industries in the UK currently do not use these advanced wastewater treatment systems for full water recovery since their performance has not been fully analysed to date by using computer-modelling techniques,” he commented.

The three-year, £402,000 project was funded by the Technology Strategy Board under the Technology Programme. The aim was to use the latest modelling techniques coupled with measurements taken from electronic sensors and using biochemical laboratory testing, to make these advanced wastewater treatment plants more energy efficient and cost effective for industrial companies.

These advanced methods which use ultra-filtration membranes produce wastewater of excellent quality which is suitable for recycling and could potentially save industrial companies many thousands of pounds in water utility costs.

Membrane bioreactors consist of a biological reactor containing a very high concentration of selective bacterial micro-organisms which ‘digest’ organic contaminants generated from the manufacturing processes. Wastewater is then pumped through an ultra-filtration membrane to remove inorganic pollutants. It is then clean enough to be reused as a secondary supply of water, or can be further purified using finer membranes and disinfection procedures.

The main operational energy costs are due to aeration of the micro-organisms in the bioreactor and having to pump liquid through the membranes at high pressures.

During the project, computer models were used to maximise the biological aeration processes which inject oxygen into the bioreactor and to minimise membrane fouling caused by the accumulation of solids during the filtration process which can reduce clean water production rates and potentially damage the expensive membrane modules.

“Using membrane bioreactors will help to improve upon the sustainable capabilities of any industries that use large volumes of clean water,” Paul added.
“We hope that the results will encourage industry to take advantage of these treatment systems as it could help them to be more environmentally friendly and reduce their operating costs at the same time.”

The project was carried out by the PC-WSS research group in collaboration with industrial partners, including: Aquabio Ltd, a UK SME company specialising in novel and advanced wastewater treatment methods especially using membranes; ITT Sanitaire (UK), a subsidiary of a large US company with a board interest in all aspects of the water engineering sector; and Northern Ireland Water, a Government-owned water utility company.

Parneet added: “Our project objective was to use computer models to better predict plant performance, and therefore increase the take up of this new technology.

“Recent technological developments and a continuing radical change in attitude towards waste generation mean that new, advanced solutions are increasingly becoming available for industrial clientele. UK research has to lead the way in introducing these new systems to a wider industrial audience.”

The PC-WSS research group, led by Professor Bogumil Ulanicki, researches and develops computer-based methods for solving engineering problems in the water industry. PC-WSS is one of the leading independent UK research and development groups in water research and provides a range of tailor-made services including consultancy, software development and training.