As populations have grown, the stress between mankind and the local water supply has also grown. On one hand, discharges of waste from our industrialized society into rivers degrades the natural water quality. On the other hand, water demands from a large population can exceed the local supply of high quality fresh water, creating a need to consider using lower quality sources such as brackish groundwater or municipal wastewater. Advanced treatment technologies can address both sides of this problem, protecting the environment from contamination and making poor-quality water safe to drink.
Nutrients (nitrogen and phosphorus) and microconstituents are contaminants of primary concern in natural systems. Excessive concentrations of nutrients can disrupt sensitive ecosystems through the process of eutrophication, whereby high nutrient inputs can lead to excessive algal growth, with depletion of oxygen due to decaying algal biomass. Requirements for nutrient removal are already reaching the limits of existing technologies for many treatment plants, and so new strategies are critically needed. Microconstituent pollutants include a diverse group of chemicals, including pharmaceuticals, personal care products, industrial chemicals, and natural and synthetic hormones. They are receiving increasing attention due their detection in wastewater effluents and receiving waters, and their known and suspected disruption of ecosystems. Microconstituents have diverse chemical properties, so some can be removed in conventional wastewater treatment systems but others cannot. Improved technologies are needed.
Wastewater treatment is primarily a biological process, and development of specialized media to support biofilms can dramatically improve the effectiveness of wastewater treatment plants for removing both nutrients and microconstituents. Submerged biofilm systems are seeing increased use, largely because of their demonstrated effectiveness for improving nitrification. Integrated fixed film activated sludge (IFAS) systems typically consist of small plastic media (see picture at right) added to activated sludge reactors to provide biofilm attachment surfaces, thereby creating hybrid systems with both biofilm and suspended biomass phases. There is little published research on how the attachment media can be designed for improved performance. Professors and students in the CWE are conducting research to develop new attachment media for systems capable of previously unattainable levels of performance.
When high-quality fresh water is in insufficient supply, it is increasingly necessary to use alternate supplies of water such as seawater, brackish groundwater, and treated wastewater. Alternate supplies have poorer quality and therefore require more extensive treatment to make them suitable for potable or other uses. A common technology for removing a wide range of dissolved contaminants from water is reverse osmosis (RO). However, RO generates a large, concentrated waste stream, which typically varies from 20 to 50 percent of the feed water. This concentrate stream is a substantial waste of water resources, particularly in areas where there is a strong incentive to beneficially use every drop of water. The contaminants from the feed water are collected into the concentrate stream, which is then so contaminated that it cannot be easily disposed of. In many cases where RO has been considered, management of the waste stream is the most significant technical and economic obstacle. Thus, advanced treatment technologies that can achieve the removal effectiveness of RO without the shortcomings are needed. Research in the CWE has led to a patented technology the incorporates an innovative combination of ion exchange and RO to achieve significantly higher recovery of water than conventional RO. Research is also in progress to develop technologies to prevent silica scaling of RO membranes, a common problem in brackish groundwaters.
Another problem with reverse osmosis is that it is very energy intensive. Faculty and students in the center are exploring direct contact membrane distillation as an alternate desalination technology—one that can desalinate water or treat wastewater without the high pressure pumps needed for RO. Membrane distillation relies on low grade heat for the driving force, and as long as waste heat is available from other processes, membrane distillation could be a solution for desalinating water without the energy intensity of RO.
Read more about the specific research projects being done in the CWE.