Improving Effluent Quality with an Overloaded Asset
About
A UK municipal based Conventional Activated Sludge Asset with an influent load 140% of design.
Background
A UK Water Company carried out a series of full-scale demonstrations at various municipal wastewater treatment works some of which received industrial discharges. This WWTW, with a design PE of 16,267, was used as a control as there were no industrial discharges and asset was operating within discharge consent at beginning of demonstration. The on-site, full-scale demonstration took place over a period of 8 months with the support of the Water Company in terms of operational, oversight and validation of results.
Performance Summary
Plant performance shows the effects of severe organic and suspended solids overload, with poor settleability (high SVI). Specific indicators of loading conditions measured during the demonstration relative to design loadings were:
– Limited oxygen transfer efficiency (required installation of new diffusers)
– Works was overloaded 125% for BOD and 143% for Suspended Solids during the test Period
– Works was at 89% of design flow for the test Period @ 4044 m3/d
Over a period of 8 months the demonstration resulted in a positive transformation in process performance across the following range of indicators:
– The capacity of the asset was increased by 19.7% for BOD and 31.6% for Suspended Solids removal.
– Settleability of the biomass improved by 12%
– Effluent quality was improved significantly: BOD 57%, Suspended Solids 46% and ammonia 10%
– 40% less solids produced using normalised data without optimisation of the operation
OPEX was reduced significantly: Polymer usage 40%, electrical 27% and exports 22%
Benefits to the Utility
– Improved settleability made the operation more stable
– Ability to sweat the asset by obtaining more throughput: BOD 125% and TSS 143%
– Improved effluent quality despite overloaded situation and limitations of oxygen transfer
– Reduced solids production. With optimization solids production could be reduced further
confirming results found in USA where typically 60%+ reduction is observed
– The Biofermentation® Program demonstrated the ability to be “revenue positive” for OPEX with no CAPEX required
– The technology provides the Utility with the ability to meet a significant portion of the UK 2030 Net Zero Carbon targets.
