This document sets out the general principles for, and provides guidance on, the quantitative characterization of the energy consumed by industrial biological wastewater treatment systems. It does not aim to characterize the treatment pollutants removal performance or process reliability or any other consideration in the selection of a wastewater treatment system.

This document includes the following sub-systems of biological treatment system:

— Biological reactors, which might be suspended growth or fixed film processes or a combination thereof, and can include anaerobic, anoxic and/or aerobic tanks and/or zones.

— Solid-liquid separation processes such as sedimentation, flotation, or membrane filtration, used for clarification of the water before discharge to downstream processes, which can also involve the return of a the separated solids as sludge back to the biological reactor.

— Any pumps, blowers and mixers for water circulation, mixing and air supply in and between the sub-systems listed herein.

— Heating or cooling of the water for treatment.

This document does not include the following subsystems of the biological treatment system:

— Wastewater feed pumps.

— Pre-treatment systems, which for the purposes of this document also include preliminary and primary treatment processes, such as but not limited to, screening, sedimentation, dissolved air flotation, chemical oxidation, oil separation.

— Post-treatment processes, such as but not limited to, disinfection, desalination, ion exchange, sludge treatment and handling systems.

— Site lighting or any energy consumption involved in office operation.

— Energy recovery from processes such as anaerobic reactors producing biogas.

Filtration processes, which are sometimes part of the biological treatment process and at other times part of the post treatment, are referred to separately within this document.