Water Resources Research Act Program

Details for Project ID 2020MO258B

Preoxidation strategies to improve treatment of algal bloom impacted source water

Institute: Missouri
Year Established: 2020 Start Date: 2020-02-28 End Date: 2021-03-01
Total Federal Funds: $22,000 Total Non-Federal Funds: $46,383

Principal Investigators: Dr. Kimberly Parker

Abstract: Project background: Harmful algal blooms (HABs) impact reservoirs for drinking water in the Midwestern U.S. During HABs, two common classes of algal toxins, microcystins (MCs) and cylindrospermopsin (CYN), can reach levels above the Advisory Concentrations set by the U.S. EPA and threaten drinking water quality. A key initial step in more than 70% of drinking water facilities in the U.S. is the addition of preoxidants including chlorine, chloramine, chlorine dioxide, or permanganate. These preoxidants are used to achieve an array of treatment goals apart from toxin removal. During HAB events, plant operators must decide whether preoxidants should continue to be applied, and, if so, at what dose. To support this decision, it must be known whether the selected preoxidation regime is able to sufficiently reduce algal toxin concentrations in the finished drinking water. The successful removal of toxins must be balanced against the formation of carcinogenic disinfection by-products (DBPs) by reactions of the preoxidants with organic constituents in the water.Project goal and objectives: The goal of the proposed research is to enable the informed selection of preoxidation strategies to treat surface water impacted by HABs in the Midwestern U.S. To this end, we will evaluate the effect of four common preoxidant types (i.e. chlorine, chloramine, chlorine dioxide, permanganate) on toxin degradation and DBP formation during the treatment of surface water. The proposed work is divided into the following objectives:Objective 1: To determine the extent of algal toxin degradation upon application of preoxidants to surface water. First, we will measure the degradation of the toxins MC-LR and CYN by each preoxidant in laboratory-grade water. For preoxidants for which toxin degradation is observed in the laboratory-grade water, we will then investigate toxin degradation by preoxidants in the presence of surface water constituents including natural organic matter (NOM) obtained from samples collected from a Missouri reservoir and algal organic matter (AOM) obtained from cultivated Microcystis aeruginosa. Objective 2: To determine the effect of preoxidants on DBP formation in HAB-impacted water. We will assess DBP formation upon the addition of each preoxidant to the same NOM and AOM samples used in Objective 1. In addition, we will evaluate the impact of the preoxidants on the abundance of organic compounds that serve as precursors to DBP formation by chlorine or chloramine applied as a post-disinfectant in the requisite final step of a U.S. drinking water treatment train. Objective 3: To evaluate preoxidant strategies on the basis of toxin degradation and DBP formation under different source water scenarios. Finally, we will integrate our results from Objective 1 & 2 to analyze the implications of preoxidant type and dose for the quality of the finished drinking water. We will consider different scenarios for selected source water parameters (e.g., concentrations of algal cells, toxins, NOM) and evaluate water quality based on toxin and DBP concentrations in the finished water. Anticipated benefits: The proposed research will enable the selection of preoxidation strategies to protect drinking water quality in HAB-impacted waters in the Midwestern U.S. Specifically, we will yield new knowledge on toxin degradation and DBP formation due to preoxidation of AOM and NOM-containing water. This project will support the training of a graduate student who will gain expertise in investigating algal toxin removal and DBP formation during drinking water treatment.