The average American uses over 100 gallons of water daily, contributing to the 35 billion gallons of sewage that are produced in the United States each day. Thousands of sewer districts across the nation are unable to treat this huge volume of wastewater to suitable standards, resulting in the pollution of natural waters through the release of poorly treated effluent.

In 1972, the United States government passed the Clean Water Act with hopes of establishing nationally-uniform secondary treatment facilities for higher effluent quality. Five hundred forty-one billion dollars later, hundreds of plants across the nation still lack secondary treatment and water quality is not much better than it was 20 years ago. Thousands of sewer districts across the United States cannot afford to improve their primary treatment facilities, let alone construct new secondary treatment structures. In the face of fiscal impossibility, an alternate solution to improve the nation's wastewater treatment systems must be found.

The use of titanium dioxide (Ti02) in municipal sewage treatment represents a low-cost alternative to the billion-dollar secondary treatment process. Although it has only been tested in cleaning up oil spills, we propose that TiO2 could be used to purify wastewater. In the presence of sunlight, TiO2 has been shown to accelerate the natural decomposition of low-level organic compounds in aqueous solutions to carbon dioxide and water. The purpose of secondary treatment is the same -- to remove organic compounds. In contrast to conventional treatment which relies on the use of potentially dangerous E. coli and chemical disinfectant with sodium hypochlorite and chlorine, titanium dioxide is safe to the point of being edible. It is a commonly used food additive. If TiO2 were to be used in municipal wastewater treatment, secondary treatment could be eliminated, resulting in billions of dollars of savings and improved effluent quality.

We conducted an experiment to test Ti02's ability to purify wastewater. Samples that had undergone primary treatment were collected from the local sewage plant and titanium dioxide powder was purchased from Sigma Chemical Company. Earlier research had indicated that Ti02 must be applied in approximately the same proportion as the organic compounds it is to degrade. Since only one percent of untreated wastewater is actually impure, titanium dioxide was added at one percent of the total volume. The treated water was then placed underneath either a grow lamp (that mimics the spectrum of sunlight) or a long wave UV (300- 400 nm) lamp, for seven hours, the time usually taken by sewage treatment plants for purification. The samples were placed on magnetic stirrers to ensure that the TiO2 powder, which is denser than water (3.8 g/l) did not settle to the bottom. Untreated primary effluent, raw sewage, and final effluent were included as controls. At the sewage plant's laboratory, we performed the following tests on the samples: biochemical oxygen demand (BOD), suspended solids, and pH.

In our model, TiO2-treated wastewater would be sent to the primary settling tanks, where sewage particles are allowed to settle via gravity. This creates the perfect opportunity to allow the titanium dioxide to settle to the bottom and the water to be skimmed off as clean effluent. The TiO2 could possibly be retrieved and reused when the sludge is removed. Since Ti02 would have already removed more suspended matter and organic waste than required by federal standards, secondary treatment could be completely bypassed, saving time, enhancing efficiency, and reducing the need for certain steps, such as disinfecting chlorination, which renders the water undrinkable. There would be no health risk if some TiO2 residues were left in the effluent or sludge; it is very safe and is a commonly used food additive.

Our novel treatment plan would save billions of dollars, eliminating the need and cost of the construction, operation, and maintenance of secondary treatment structures. This fiscal savings would not be compromised by an environmental debt. Ti02 exceeds federal standards, removing even low-level organic carcinogens not eliminated under current processes. Wastewater effluent would be of significantly higher quality and thousands of communities across the United States would be able to enjoy pristine natural waters without spending huge amounts of revenue on treatment structures. Ti02 should be seriously considered as a strong candidate for enhanced sewage treatment.u