Foaming of conventional activated sludge (CAS) is very common. It may happen during start-up due to the presence of surfactants, with insufficient biomass to degrade them during the early stages. However, this is normally a short-term issue. These foams (from surfactant foaming) are mostly white and can be countered with anti-foamants until there are sufficient biomass developed to degrade them.
Features - Feasibility, optimisation and costs
Operational experience at La Center WWTP in Washington, USA indicates that the cost of MBR technology may be lower than that of a conventional biological treatment process, despite the higher energy demand. La Center is a small city in Clark County, Washington, USA, with a population of 3,100. The wastewater treatment works at the town was originally constructed in 1967
There has been a recent surge of interest in anaerobic MBRs. The technology provides the potential for removing COD with a net energy benefit from the methane generated, albeit without nutrient removal. Interest within academia is evidenced by the publication of five independent reviews of the subject in various learned journals in 2012 alone.
In Japan, there are over 3,000 MBRs which have been in operation since the 1980s for small-scale on-site industrial/household wastewater treatment. However, municipal wastewater applications began only in the mid 00’s, leading to 19 operational full-scale plants by April 2013.
This feature summarises recent research into a new membrane bioreactor technology applied for water reuse (NEWater, Singapore) with reference to energy demand. Reducing aeration demand for membrane air scouring combined with a high flux has been shown to significantly reduce energy demand.
The Arenales del Sol WWTP in Spain combines biological treatment with nutrient removal with a submerged MBR system fitted with flat sheet (FS) ultrafiltration membranes, with an average treatment capacity of 10,000 m3/d (10 MLD). The plant provides high quality treatment to highly variable seasonal sewage inflow due to the nature of this popular coastal region.