For sites operating a biological effluent treatment plant (ETP), maintaining compliance with discharge consent limits during start-up or post-shutdown periods presents a significant challenge. When biomass within the ETP becomes weakened or depleted, it can take several days or even weeks to re-establish a stable microbial community. This recovery delay increases the risk of non-compliance once production resumes.
Any breach of Environmental Protection Agency (EPA) CAR or Pollution Prevention and Control (PPC) licence conditions is a serious concern, potentially leading to enforcement actions, financial penalties, or criminal prosecution depending on the nature and severity of the incident. With the Environment Agency often conducting sampling immediately after production restarts, there is a considerable risk that ETP discharge may exceed consent limits.
Fortunately, there are two practical, cost-effective strategies available to help mitigate these risks and ensure a smooth, compliant restart: artificial wastewater feed and bioaugmentation.
Artificial Wastewater
An artificial wastewater feed provides an alternative or complementary solution during plant shutdowns. It serves as a sustaining nutrient source to maintain microbial activity when normal effluent flow is suspended.
Biological treatment systems rely on organics within the wastewater as their primary food source. Without it, microbes may starve, lose activity, or die off. Supplying an artificial wastewater during shutdown periods prevents microbial decline, reduces the risk of bulking or foaming, and inhibits the growth of opportunistic filamentous bacteria. Maintaining an active, balanced biomass ensures a rapid recovery of full treatment efficiency when manufacturing resumes, reducing the risk of non-compliance.
OMEX Environmental provides Nutromex 940PP, a formulated artificial wastewater containing carbon, nitrogen, and phosphorus in the optimal 100:5:1 ratio for microbial growth, along with a blend of essential trace elements. The product should be dosed at a reduced, maintenance rate during shutdowns to sustain microbial activity and then gradually tapered off as normal effluent flow resumes.
Bioaugmentation
Bioaugmentation involves introducing specialised microbial strains into a biological wastewater treatment system to accelerate recovery and stabilisation following a shutdown. During downtime, when effluent flow ceases, the existing microbial population can become inactive, unbalanced, or die off due to the lack of organic feed (BOD). By adding a robust, active microbial culture, operators can re-establish biological activity quickly, reduce start-up time, and enhance treatment performance during the critical restart phase.
OMEX Environmental offers the Micromex EU range of bioaugmentation products, specifically developed to optimise biological activity in aerobic ETPs. The formulation contains five distinct bacterial strains, cultivated under controlled conditions to maximise population density, viability, and degradation efficiency for effluent BOD. Micromex can be mixed with water and dosed into a closed bio-tower or added directly to an open MBBR surface. Where possible, it is recommended to run the ETP in recirculation mode for 24–48 hours prior to production restart, or alternatively slow the inflow rate to allow the microbial community to reach a sufficient size to manage the incoming BOD load—helping to maintain discharge compliance from the outset.
Summary
Whether through bioaugmentation or artificial wastewater supplementation, operators have access to reliable, easy-to-implement, and cost-effective solutions to maintain biological health during ETP shutdown periods. These strategies not only safeguard compliance but also ensure a faster and more stable return to optimal treatment performance.
OMEX Environmental Ltd offers both the products and the technical support required to successfully implement these solutions—helping sites maintain operational continuity and environmental compliance with confidence.