The natural solution to wastewater treatment

Transcription

1 April 2009 The natural solution to wastewater treatment The need for sustainable wastewater management strategies is increasing. Utility companies and industry must comply with wastewater treatment regulations and Clodagh Murphy, IEMA member, argues that reed bed technology is the solution to future-proofing treatment systems for the expected changes in climate and the economy. It is not just about complying with regulations. Over recent years, corporate social responsibility (CSR) reporting has become an essential part of business accountability. While we are now operating in a greatly changed economic environment it is important that companies do not lose sight of their CSR commitments. Compliance whether enforced or voluntary is not an issue that will go away just because of the downturn in economy. The Groundwater Directive, Urban Wastewater Treatment Directive (UWWTD), Landfill Directive and, ultimately, the Water Framework Directive (WFD) are among several EU directives which govern the way in which wastewater should be managed in the UK. The various directives have implications for all sectors whose business activities directly or indirectly affect the water environment from the water industry itself through to agriculture, construction and manufacturing. In fact, all businesses which have discharge consents or trade effluent licences will find operational and financial efficiency improve if they look at their wastewater management from a sustainability perspective. If left untreated, wastewater can affect surrounding water quality as well as altering the distribution of plant and wildlife and upsetting the balance of ecosystems. This pollution may affect sites far from the original source and, as such, must be carefully managed. One way in which this can be done is through the use of reed bed technology. The use of reed beds to treat dirty water is not a new idea. In fact, records indicate their use for this purpose 2,000 years ago in China. It is, however, only relatively recently that their application has been considered more scientifically. Reed beds have been used successfully throughout the UK since the 1980s. In the past decade the use of reed bed treatment systems to treat wastewater has increased

2 dramatically. The technology has been applied in numerous environments from airports to landfill sites, hotels to distilleries, and sewage treatment to vegetable washing. Years of research and development have led to reed bed treatment systems being successfully applied to a wide range of effluents and industries and used to remove contaminants such as organic waste, hydrocarbons and heavy metals. Technology The design and engineering of a reed bed treatment system is primarily determined by the discharge consent but also takes into account a number of factors, including the volume and nature of the wastewater, available space, and the upstream treatment processes being used. There are different types of reed bed, which are selected on the basis of the specific treatment requirements; however, the principle of how they work is the same. In essence, biological, chemical and physical treatment of the wastewater is achieved via filtration through a soil or gravel matrix in which the reeds are planted. Bacteria thrive in the matrix and break down the contaminants. Reed bed technology can play an integral part in meeting compliance targets. The following examples, from different market sectors, all started from the objective of managing wastewater treatment sustainably in such a way as to meet all compliance requirements while balancing the business considerations of profitability and efficiency. Water companies ARM has been working with water companies to develop reed bed technology for over 20 years. The adaptability of the technology means that reed beds are able to complement existing treatment solutions as well as extending the asset life of valuable active facilities and failing treatment plants. To meet the requirements of the UWWTD, every water company has had to make large investments over recent years in building and improving treatment works as well as improving sewerage systems. The majority of water companies use reed bed technology, however, Severn Trent is the largest user with reed beds for sewage and stormwater treatment on 370 of its sites. Southern Water has the largest reed bed providing tertiary sewage treatment in the UK, while the second largest is at Berkhamsted for Thames Water. Dwr Cymru Welsh Water s wastewater treatment works at Crynant has undergone a complete design overhaul to meet tighter water discharge consents which now include ammonia. As a result of the redesign, the works can now treat up to 90 litres of wastewater per second thanks to a 2,400 square metre vertical flow reed bed.

3 Likewise, Anglian Water has been using reed beds for a number of years and has recently been exploring the benefits offered by floating reed beds on sludge lagoons. Landfill sites It is not just water companies benefitting from reed bed technology to assist with compliance requirements. In 2002, the EU Landfill Directive came into force in the UK as the Landfill Regulations. These regulations cover the management of existing and new sites with the aim to prevent negative effects on the environment and surrounding groundwater from the landfill lifecycle. Landfill sites are open to the elements. Rain falling on the site permeates through the layers of waste. This, combined with the resulting liquid from the decomposition process, produces a leachate which is typically difficult to treat. Reed bed treatment systems have proven an effective solution to this challenge. Re-using wash water in vegetable processing The food and drink industry is one of the largest users of water and producers of wastewater. Water efficiency is integral for the profitable running of such companies. At an organic root vegetable farm and processing plant, near Peterborough, water is used to remove soil from the crops. The owners were looking for a non-chemical, lowenergy option to treat the wastewater created by this process and allow them to meet with compliance requirements. Reed bed treatment systems are able to remove the solids and pathogens in the wash water as well as reduce BOD and ammonia. For this particular grower, ARM designed and installed a reed bed treatment solution comprising three stages, including a floating reed bed. This process allows for the resulting reed bed effluent to be potentially reused for washing another batch of vegetables or for irrigation. The inclusion of reed bed technology allows the grower to manage its wastewater sustainably in a manner that fits with its organic ethos but is cost-comparable to the alternative mechanical and chemical treatment options. Breweries and distilleries Like vegetable processing, the production of beverages is a water-intensive process and generates large volumes of polluted water which need to be managed and treated. A study by the International Centre for Brewing and Distilling at Heriot-Watt University in Edinburgh suggests that the UK brewing industry uses an estimated 34 million m³ of water annually, over 70% of which is discharged as trade effluent. For the distilling process, it is estimated that up to 20 litres of wastewater is generated for each litre of ethanol manufactured.

4 Reed beds have been used successfully at breweries and distilleries throughout the world from India to the Caribbean and here in the UK to treat wastewater in a costcomparable and sustainable way. At a distillery in Dufftown, Scotland, belonging to one of the world s leading premium drinks companies, ARM has installed a horizontal, subsurface-flow reed bed to reduce soluble copper concentrations in the water discharge to the consented requirement of 0.5 mg per litre. Treating up to 650 m³ of wastewater per day, the reed beds at Dufftown are used as a final treatment stage to 'polish' the effluent after it has been treated in an onsite bioplant. Airport runways water runoff One of the lesser-considered sectors for treating wastewater is that of transport and infrastructure. An airport environment, for example, is made up of multiple diverse communities which have different waste streams and different requirements for the treatment of wastewater. Reed beds can be used for the treatment of surface water runoff the water that flows from hardstandings and runways as a result of rainfall and washdown. Large volumes of water and environmentally-harmful chemicals are involved in airport maintenance including herbicides, pesticides, de-icers containing glycol and fire-fighting foam. The runoff from these activities requires treatment before discharge as the contaminants can have significant impacts on the quality of surrounding water. As with all industries, ignoring it is not an option. The Environment Agency and SEPA (Scottish Environment Protection Agency) impose fines for any pollution caused by insufficient treatment or preventative action being taken. ARM has designed and installed one of the first reed beds at an airport and international fire training centre engineered specifically to treat fuel and fire-fighting foam run off from training exercises. Floating reed bed technology can also be engineered to dissuade large birds from collecting around the airport and possibly causing expensive and potentially fatal damage to the aeroplanes. Focus on the hospitality sector Compliance is not just an issue for big business and infrastructure. A large number of hospitality and tourism sites are located in remote locations without access to mains sewer. They may still, however, be producing enough wastewater to be regulated and require treatment. In these cases reed bed technology can offer a viable alternative. The beds can even be designed in such a way that people won t know it is a sewage treatment facility and can incorporate aesthetic habitats if appropriate. A growing awareness of environmental responsibility combined with good commercial practice has led to hotels, spas and conference centres re-considering their approach to resources, wastewater and energy use more seriously.

5 Many visitor attractions, tourist information centres and holiday accommodations are now assessed under green criteria managed through the Green Tourism Business Scheme (GTBS). A well thought-through reed bed treatment system can help meet the criteria for these assessments. Considerations for the future Of course, it must be recognised that the capital investment in a reed bed is a significant consideration. However, reed beds are able to show significant savings during their lifetime because of reduced maintenance and no or low power requirements. In comparison to conventional treatment plants, reed beds require very little ongoing attention. In order to maintain optimum performance, however, it is necessary to implement a regular maintenance schedule. Reed bed treatment systems offer an attractive treatment solution to wastewater challenges from both environmental and maintenance perspectives. They are often selected because of their reliability. Where other treatment technologies may fail because of mechanical or electrical faults, the vast majority of reed beds can be engineered to use gravity flow so there is no need for pumps and electricity. In locations where the existing sewage treatment no longer satisfies more stringent quality standards reed beds can provide a sustainable, long-term solution. They work well in the treatment of secondary and tertiary effluents and help reduce failures in existing treatment works. Over the last 30 years, reed bed technology has been proven repeatedly through research and development as well as the extensive use of engineered systems within industry and municipal treatment. However, there are still plenty of opportunities for the water industry, and those affected by its activities, to explore the benefits and potential applications of reed bed technology. Sludge treatment reed beds can be used for the dewatering of sludge at small treatment works to minimise transport costs involved in tankering the sludge away. Reed beds which provide additional storage and treatment for stormwater have also proven successful and are being more widely used by the water companies to manage storm events and future proof their assets to cope with the expected future climate. Climate change is very likely to affect a wastewater system during its asset life. It is not just the water companies which need to take this into account. Every company should be assessing whether it is beneficial to future proof new assets. Reed bed technology is one solution to the challenge of sustainable precautionary asset design. It provides the requisite flexibility so that assets can be easily upgraded as required while keeping lifetime expenditure to a minimum and responding to the need to prepare for the future. Reed beds should be seen as a must-have element of sustainable wastewater management systems not just a nice add-on.

6 words Kinetic Communications