Waste and recycling - Case study
| Every vial has a silver lining | Meter recycling | Sludge disposal solution | Spoil recycling |
As a part of our commitment to deliver excellent customer service, and as part of our meter strategy, we have implemented a programme to replace customers existing water meters as they reach 15 years of service, this will ensure
that readings remain accurate. The programme will be phased in over a 10 year period, and will then become a rolling programme. We will be replacing around 100,000 meters in the initial 5 year period (2010-2015) of the programme and this will increase to around 400,000 in the subsequent 5 years.
A vital part of the replacement programme is the disposal of the removed meters. The majority of the old meters are made of either brass or cast iron with a mix of metals within the internal workings. As part of the overall meter strategy, we have put in place a project to ensure that all the old meters removed are recycled to allow the metals to be reused, reduce the overall carbon emissions from the programme and divert the removed meters away from landfill.
We are also ensuring that the programme is delivered efficiently. The programme will be delivered as part of our meter reading programme and meters will be replaced at the time that they are normally read which means that no additional journeys will be undertaken and no additional carbon emissions will be made.
Sludge disposal solution
As an industry we are under increasing pressure to minimise our waste production, find alternatives to landfill disposal, and follow the waste hierarchy of reduce, reuse and recycle (the 3 Rs) so as to minimise the associated environmental impacts of waste disposal and landfill use. The disposal of waste water sludge has always been one of our primary waste concerns, it represents a huge portion of our waste products, and we are constantly looking for improvements on current processes and new innovations to reduce this volume of waste.
In the Northumbrian Water region, there are more than 400 sewage treatment works that all produce varying amounts of sludge. This material has to be removed from every works, it is difficult to handle, is high in volume and can have odour issues.
Northumbrian Water had been using conventional anaerobic digestion techniques for about 5% of our sludge in order to create a valuable organic product (bio-solids) as well as capture methane to create energy at these plants. The technique utilises the natural oxygen-free decomposition process (hydolysis), by which organic material breaks down, to produce biogas, (which is approximately 65% methane and 35% carbon dioxide), this safe and natural decomposition reduces the quantity of recyclable bio-solids. The latter is safely recycled as an agricultural fertilizer and by returning it to the soil in this way, nutrient and organic levels are ‘cycled’ to ensure efficient crop management.
Technology has advanced significantly in the past five years and a technique has been perfected that enhances the process of thermal hydrolysis, known as Advanced Anaerobic Digestion(AAD). AAD significantly enhances the benefits of anaerobic digestion by separating and optimizing the key process stages used in conventional digestion systems. The improved processes result in increased biogas production, and therefore energy creation, with a corresponding reduction in the volumes of bio-solids produced.
Due to the obvious benefits AAD offers, we invested in a completely new AAD plant at our existing sludge treatment centre at Bran Sands on Teesside. The new plant started treating sewage sludge in December 2009. The facility is our largest site, and treats sludge from all of our sewage treatment works south of the River Tyne and in the Tees Valley, which represents a population equivalent of 1.9 million people The plant will generate 4.7 MWe from the four on-site CHP engines.T the energy recovered from the sludge treatment process goes a long way towards making the entire wastewater treatment process on site energy self-sufficient, this eliminates the need for large amounts of grid electricity and has the dual benefits of cutting energy use and costs.
There are additional benefits of having this AAD strategy too:
• building several sludge dewatering centres around the region allows us to ‘dewater’ sludge from the sewage works, and allows us to transport a ‘cake’ and not the wasteful transportation of large amounts of water associated with liquid sludge tankering, therefore reducing our transport cost and associated emissions.
• maximising nutrient recovery from sludge which was previously not optimised.
• the bio-solids produced are a Class A Product, which is safe, containing no detectable pathogens and has minimal odour impact and is a valuable agricultural fertilizer.
• energy from sewage sludge, is classed as renewable and therefore contributes to our commitments to producing and utilising renewable energy and reducing our carbon impact.
AAD has provided us with a regional sludge management solution in line with both our strategic direction statement, and with the added benefits of following the 3R waste minimisation strategy, and creating renewable energy and thus reducing our carbon footprint. Bran Sands is the first phase of Northumbrian Water’s AAD strategy. A second plant is already planned for Howdon, on Tyneside, and received regulatory approvals and planning consents in late 2010. We are also investigating opportunities for co-digestion of other organic materials (eg food wastes), this will allow us to support other organisation within the North East by giving them an alternative to landfill disposal of wastes, this allows them to fulfil their reduction in landfill obligations.
Every vial has a silver lining
We are constantly looking for ways to improve the way we work and reduce the amount of waste we produce. We believe in the reduce, reuse, recycle ethos. Our laboratories at Howdon have applied this principal to the way they work and have vastly reduced the amount of disposable testing vials, micro test tubes, they use to conduct the sample testing that helps us to protect the regions rivers.
In order to recycle as much material as possible, the scientists in the laboratories have switched to a new way of working. Now, once the vials have been used, they are returned to Hach Lange, the company that supplies and recycles the vials, and elements, including the silver, are reclaimed for re-use. The previous method used three times as much chemical and created ten times more waste.
As a result of this change in behaviour, and in recognition of the laboratory’s commitment to recycling, our laboratories at Howdon have been presented with a symbolic ingot of solid silver. The 80 gram bar of silver is one of thirty reclaimed from 300,000 waste water glass testing vials used in the last eight years and is a shining reminder of the importance we place on sustainable solutions, innovation and environmental management.
Spoil recycling
We have an arrangement with Northumbrian Roads to collect and recycle the excavated materials produced by our repair and maintenance works. Where recycling bays exist Northumbrian Roads collect, recycle and return the material in a form that is then utilised for backfill and pipe bedding requirements. The materials are subject to independent assessment and it is our policy to use recycled materials wherever possible.
The ongoing project has proven such a success we are expanding the use of the scheme to other sites within the business.