Many small drinking water systems are at a comparative disadvantage due to their size (e.g., limited financial and human resources), and sometimes due to their remote location. The challenge in meeting emerging regulations can be a formidable one. The objective of this research is to test the ability of ferrate oxidation to solve a wide range of water quality and treatment problems faced by small systems. The general working hypothesis is that ferrate is: (1) more effective and less prone to unwanted side effects than conventional technologies such as chlorination, chloramination, and permanganate oxidation, and that it is (2) comparable in performance to advanced technologies such as ozonation or chlorine dioxide oxidation that are more costly, more hazardous or require specialized expertise to operate.

Bench-scale experiments were conducted using raw water from numerous drinking water systems representing a wide range of quality characteristics and treatment needs. In general, primary treatment goals included the oxidation and removal of inorganic contaminants such as iron or manganese in the presence of dissolved organic material (3-5 mg/L TOC).  In this way, the ability of ferrate to oxidize various contaminants while producing lower levels of regulated disinfection by-products than other common oxidants was assessed. In addition, some samples were spiked with wastewater contaminants, in an effort to understand the ability of ferrate to control such trace contaminants under conditions typical of water treatment.  Conditions (e.g., ferrate dose, pH, etc.) were established to achieve a range of treatment goals.

Results from the bench-scale experiments indicate that ferrate is a powerful oxidant that rapidly oxidizes inorganic contaminants such as iron and manganese.  However, fractionation of oxidized metals shows that oxidation with ferrate often yields colloidal particles that may challenge subsequent treatment processes. These particles could be effectively destabilized through charge neutralization.

In the presence of naturally occurring organic matter, oxidation of inorganic contaminants was negatively affected.  Complete oxidation of iron and manganese in waters with elevated TOC required many times the estimated stoichiometric dose for complete oxidation and removal.  Analysis of  chlorine demand and disinfection by-product (DBP) formation following ferrate addition showed slightly decreased chlorine demand and lower amounts of DBPs.

Data from the bench-scale experiments will be presented and conclusions will be drawn regarding implications for treatment at the full scale.  We will provide guidance for the beneficial use of ferrate in small systems and highlight the ways it can be used to improve water quality, lower cost and provide a more sustainable treatment alternative to other technologies.