One of the end products of wastewater treatment, biosolids has historically been considered a liability, rather than a material that can make a genuine contribution to sustainable farming. Following the introduction of the Safe Sludge Matrix and Sludge Code of Practice, the recycling of biosolids to agricultural land is now accepted as the best practicable environmental option, where this market is available. However, that doesn’t always mean that sludge management is simple or that the market always appreciates the contribution that biosolids can make. Aqua Enviro’s experience of both the water and agricultural industries ensures we are ideally placed to assist in establishing and/or optimising a recycling service.
Biosolids Assurance Scheme
Building on existing approaches, the launch of the Biosolids Assurance Scheme (BAS) aims to provide additional reassurance to food chain stakeholders concerning the use of biosolids, while increasing market acceptance and confidence in the quality of the product. When combined with long-term volatility in fertiliser prices, this increased confidence means that the majority of water companies can now charge at least a token amount for their biosolids when supplied to farmers. Whilst there will always be variation in the amount that individual water companies can charge for biosolids (due to geographic factors and other influences), there is no reason why sludge recycling and biosolids’ market development cannot be optimised at the individual or collective treatment centre level. We can offer impartial advice on supply/service models, develop positive marketing strategies and recommend approaches to overcome any local constraints to biosolids’ use. The Bioresources team can also assist with all elements of quality management, including: HACCP planning; selection of pathogen management options; source material risk assessments; BAS compliance, pre-audit checks and ongoing accreditation.
Characterisation of material
Alongside our market-facing expertise, the detailed technical process knowledge can also help optimise production techniques (including THP, anaerobic digestion, liming and dewatering), therefore reducing costs and improving profitability. In addition, using our in-house laboratory we can investigate new treatment approaches at bench scale – before taking promising approaches to pilot.
A key test is the Dewaterability Optimisation Tool (DOT). The DOT tester compares potential and actual dewatering performance, allowing a wide range of different dewatering approaches (e.g. polymer formulations and doses) to be tested at a reasonable cost. This allows subsequent on-site investments to be targeted at approaches that will have most impact.
Another useful tool is the Stackability Test, which quantifies the ‘stackability’ of the dewatered cake. This information is vital, as when biosolids are stored on farmers’ fields, they must be solid enough to be stacked in a free-standing heap and must occupy as small a surface area as is practical. Non-compliance can result in fiscal penalties for farmers. Aqua Enviro’s wider portfolio of services also includes assessment of alternative treatment solutions (such as nutrient extraction and liquor recycling) through to assessment of ‘zero sludge’ advanced thermal processes.
Upskilling to maximise the opportunity
To assist with progressive biosolids management schemes, we deliver a range of training courses that can be tailored to specific companies or individuals. General topics that are included in these training sessions are: what farmers want and how they are regulated; marketing of organic materials into agricultural and non-agricultural sectors; the impact of process changes on biosolids’ utility; improving sludge quality.
Aqua Enviro have been at the forefront of the UK biosolids industry and founded the European Biosolids & Organic Resources Conference, which has been successfully run for over two decades. Our dedicated team of engineers and scientists, combined with our in-house laboratory, ensures we are well placed to provide strategic consultancy and unparalleled advice in this field.