Membrane treatment of water is on the increase. Several factors are responsible for this trend, which is being seen in both potable and wastewater treatment. The factors include the decreasing cost of membrane equipment, which make membrane treatment more cost competitive with conventional
treatment processes, increased concern for pathogen removal, use of less desirable source water for water treatment, often with higher total dissolved solids (TDS) concentrations, and the growing desire for reuse of wastewater treatment plant effluent. The waste streams generated from membrane
treatment, however, can pose difficult problems for disposal. Since membrane treatment facilities generate high TDS permeate, sending the brine to a wastewater treatment plant can cause salt toxicity, disrupting the plant performance. Lagoon evaporation has traditionally been used to decrease
the volume of the brine, allowing the remaining concentrate to be handled as a solid. This practice is limited by its large site requirements and is often only practicable in arid climates. Consequently, alternate brine treatment technologies are being investigated, which include: Freeze concentration – directional freezing of brine forces solids concentration in the non-frozen portion of the liquid, resulting in desalted ice fraction Mechanical evaporation – addition of mechanical
energy to accelerate evaporation process and reduce space requirements Beneficial reuse of the brine – using brine stream as sodium source for on-site sodium hypochlorite generation. This paper reviews these technologies,
discussing the current state-of-the-practice, limitations, and relative costs.
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