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.
Trace organic contaminants (TrOCs) in municipal wastewater consist of a wide range of naturally occurring and synthetic chemicals (Luo et al., 2014). They include industrial chemicals, chemicals used in households, chemicals excreted by people, and chemicals formed during wastewater and drinking-water treatment processes.
While most scientific articles about MBR systems suggest membrane surface fouling as being the main operational limitation for the technology, it is widely recognised by practitioners that clogging phenomena – possibly related to inefficient pre-treatment – are at least as important. It is also recognised that clogging takes different forms...
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.
Biological nitrogen removal from wastewater typically happens through aerobic nitrification (from ammonia to nitrate) and anoxic denitrification (nitrate to nitrogen gas). This is usually carried out in two separate process tanks other than in a sequencing batch reactors (SBRs). However, it is more energetically efficient to convert ammonia directly to nitrogen gas, since it requires less oxygen.
The non-Newtonian nature of sewage sludge means that its measured viscosity µs varies with shear rate due to the shear-dependent deformation of the flocculant solids (Yang et al, 2009). Viscosity affects the shear at the membrane interface, shear being a key parameter in promoting flux, and the dependency of apparent viscosity on temperature may then also be significant in determining flux.