For the past nine years, ADAS consultants have been working with Anglian Water to provide independent bioaerosol monitoring solutions and risk assessment for the Cliff Quay composting facility.
Site background
The Cliff Quay composting facility, commissioned in 1997, is located in south Ipswich situated on site of the Anglian Water WwTW. The facility which comprises of a fully enclosed Gicom in vessel system accepts 13,000 wet tonnes of organic waste annually consisting of the following components.
• 8,000 tonnes of municipal greenwaste
• 4,500 tonnes of dewatered biosolids
• 1,200 tonnes of sugar beet waste
The design of the in vessel system at Cliff Quay incorporates three single ended batch tunnels, from which ventilated process air is passed through a water scrubber and finally a wood chip biofilter which reduces the concentration of odour and bioaerosols released from the facility.
Single ended tunnel design does however cause restrictions concerning the type of organic waste which can be treated on site due to changes to the European Animal By-product Regulations. As there is no clean end of the tunnel which comes into contact with only treated waste, facilities are unable to accept catering waste contaminated by meat. This has caused large scale £300,000 development at Cliff Quay to allow a greater spectrum of animal by-products to be accepted.
Waste which arrives on site is:
• Shredded to ensure a large surface area and even mix of compostable material.
• Composted at 60°C in the batch tunnels for a minimum of two days to allow the removal of all potentially dangerous pathogens.
• Matured for 18 days.
• Screened to ensure a consistent finely graded product.
• Sold for the purpose of improving agricultural land.
Emissions monitoring
Bioaerosol monitoring at Cliff Quay was undertaken by ADAS between 2000 & 2008, in order to evaluate concentrations of a variety of micro-organisms in the pursuance of license conditions for the newly opened in vessel facility. Originally sampling took place on an annual basis, however following a Site Specific Bioaerosol Risk Assessment carried out by ADAS in September 2002, the facility committed to a sampling strategy which involved monitoring for the following micro-organisms three times per year:
• Faecal coliforms ( E. coli)
• Faecal enterococci (Streptacoccus)
• Moulds at 37oC
• Moulds at 25oC
• Gram Negative Bacteria
• Thermophilic Actinomycetes
The bioaerosol sampling was carried out using single stage Andersen samplers according to the Association for Organics Recycling (AFOR) Standardised Protocol for the Sampling and Enumeration of Airborne Micro-organisms at Composting Facilities and included the following sampling positions:
1. Upwind boundary of the composting area.
2. Downwind of the composting area.
3. On top of the Biofilter.
4. Adjacent to the screening operation.
5. Adjacent to the nearest ‘sensitive receptor’ as defined in the ‘Standardised Protocol for the Sampling and Enumeration of Airborne Micro-organisms at Composting Facilities’.
Conclusions
Anglian Water received both comprehensive monitoring reports and a detailed Site Specific Risk Assessment regarding sampling carried out by ADAS personnel on site at Cliff Quay composting facility. By utilising the experience of ADAS’ bioaerosol monitoring service and advice provided by consultants on-site, Cliff Quay has maintained composting operations with confidence that all facility licence conditions are being adhered to and further that operations carried out have minimal impact on the surrounding environment.
Under conditions set by the Environment Agency Cliff Quay demonstrates compliance, as concentrations measured at upwind, downwind and NSR locations are below the prescribed threshold value. This can accredited to a combination of both correctly maintained and functioning technology and good practice in terms of operational management on site.
For further information on ADAS bioaerosol and odour services please contact: Charlotte Pearson, Bioaerosols Service Manager on 0845 766 0085 or email bioaerosols@adas.co.uk.