WATER & WASTE TREATMENT


FOUR STEPS TO SUCCESSFUL AD DESIGN Ensure that high level equipment can be


easily reached via steps or access ladders with a sufficient platform for working, or that there is room for a cherry picker or scissor lift. If the plant has a flexible membrane roof, you will also need to allow access for cranes, as the lifetime of the membrane is shorter than the subsidised life of UK AD plants and it will need replacing. Finally, consider DSEAR (Dangerous


Substances and Explosive Atmospheres Regulations). Avoid siting equipment that will need regular maintenance within a DSEAR zone, to reduce the time that operatives will spend in this high-risk area. 3. Protect your people The health and safety of site operatives


Consider placing pipe runs and electric cables above head height on support frames to keep floors clear for access


Steven Cotterill, 3D CAD designer for Anaergia UK, outlines the four steps to follow for successful sewage AD plant design


W


hether you’re developing a small- scale digester or a large biomethane facility, embarking on a


new wastewater anaerobic digestion project can be a daunting prospect. A comprehensive design phase to determine the most successful layout for your site can reduce the risk and ensure your plant remains profitable. Here are Anaergia’s four design cornerstones to set your sewage AD project on the path to success… 1. Follow the process flow At a well-designed wastewater AD facility,


process dictates positioning. In so far as the site footprint will allow, design the layout of your plant to follow the flow of material. This will enable feedstock to be pumped or conveyed over the shortest distance possible, reducing the likelihood of downtime from blockages and lessening wear and tear on feed equipment, process pumps, macerators and conveyors. This design principle can be applied across


the whole site. A compact layout is more cost-effective, as a smaller footprint means less land, less concrete and less labour will be required to build the plant. However, make sure to factor enough space into your design for landscaping, planting and shielding, which


42 NOVEMBER 2021 | PROCESS & CONTROL


are often required by planners. 2. Enable easy access to equipment Maintenance is vital for successful AD


operation, so ensure that forklift trucks, small vehicles or lifting machinery can easily access key equipment such as tanks, pumps and mixers. This will give service engineers the flexibility to quickly remove, repair and if necessary, replace parts and equipment, reducing downtime.


If the proposed plant has a flexible membrane roof, allow access for cranes, as at some point the membrane will need replacing


and visitors is paramount and, as stated above, full consideration to DSEAR and HAZOP (Hazard and Operability Study) must be followed. The potential for explosive atmosphere increases near to pressure relief valves, as these are a final safety measure of biogas release should the flare fail to light when excess biogas is not being consumed. Therefore, as well as siting key process equipment away from ATEX-zoned areas, try to avoid locating any electrical equipment or instrumentation within the biogas release zone. If this is not possible, then ensure that equipment or instrumentation are correctly ATEX-rated. Establish clear personnel routes


throughout the facility. Inside the reception building, provide designated walkways for operatives to follow, as well as barriers and/or handrails to protect people from tipping vehicles and bucket loaders. Arrange process pumps and associated pipework away from walkways to avoid trip hazards and consider placing pipe runs and electric cables above head height on support frames to keep floors clear for access. Take into account the maximum number of


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