Advanced Wastewater Treatments

Membrane Technology

Membrane technology is easy and well-arranged process conductions. The membrane acts as a very precise filter that stops suspended solids and other substances to pass through, while it allows water to pass through. There are two factors that determine the effectiveness of a membrane filtration processes: retention and flux. Membrane filtration can be divided into micro and ultrafiltration (MF/UF), Nanofiltration (NF) and reverse osmosis (RO). When membrane filtration is used for the removal of larger particles MF/UF are applied. The pressure that is required to perform NF and RO is much higher than the pressure required for MF/UF, while productivity is much lower (Sonune et al., 2004).

A recent advancement in wastewater treatment technology involves the filtration of wastewater through porous membranes (Sharrer et al., 2007). These technologies have introduced a new cutting edge on wastewater treatment. For concentrated wastewaters, like industrial streams and landfill leachate, MBR has been applied at full scale successfully however this system requires relatively high energy. Using new membrane techniques, like transfer flow modules, creates the possibilities of a more widespread application. MBR technologies provide the potential for reuse wastewater generated from industries or municipalities and decrease in sludge production. The MBR combines suspended growth unit responsible for the biodegradation of the waste compounds and the membrane filtration module for the physical separation of the treated water from the mixed liquor using a porous membrane that helps to retain high microbial concentration in the reactor and increase the biological operation capacity of the reactor. The MBR process was introduced by the late 1960s, as soon as commercial scale UF and MF membranes were available (Le-clech et al., 2006). The original process was introduced by Dorr-Olivier Inc. and combined the use of an activated sludge bioreactor with a cross flow membrane filtration loop (Smith et al., 1969).

Although the research on MBR technology began only few decades ago, it has developed quite rapidly and become one of the important technologies in wastewater treatment process. Up to this date, MBR systems have mostly been used to treat industrial wastewater, domestic wastewater and specific municipal wastewater. Requirement of higher removal of organic matters, suspended solids, nutrient and harmful bacteria from the wastewater and the requirement to meet the strict effluent discharge quality in terms of nutrient and micro-pollutants, the main cause for the eutrophication and decrease the water quality in the receiving water bodies, are the important issues in the present wastewater treatment processes (Ersu et al., 2008; Kraume et al., 2005). MBR technology have become a most promising process to overcome these issues and the nutrient removal from the wastewater and several studies have been focused on nutrient removal from wastewater using MBR (Galil et al., 2009; Ersu et al., 2008; Yuan et al., 2008; Kraume et al., 2005; Song et al., 2004; Adam et al., 2002; Lesjean et al., 2002).

This process have several advantages i.e. higher treatment efficiency is obtained in smaller footprints compared to conventional treatment processes, higher biomass concentrations, no long sludge-settling periods, lower sensitivity to toxic compounds and both organic and high ammonia removals in a single process, flexible in terms of shape, load and volume, minimize labour costs, no need to add any chemicals. The disadvantages are high operating costs associated with the aeration process, membrane replacement costs are high and must be budgeted for appropriately, concentrate and waste stream disposal issue (Sonune et al., 2004).