Emerging Technologies Program
After a rigorous selection process, the following four projects were selected to carry out research related to small drinking water systems. Thank you to all applicants!
Reactive Electrochemical Membranes for Simultaneous Removal of Multiple Classes of Contaminants of Concern in Small Drinking Water Systems
Graduate Students: Soroush Almassi (University of Illinois at Chicago) and Zhao Li (Villanova)
Small drinking water systems (SDWSs), serve fewer than 10,000 in population, are facing increasing challenges to comply with regulatory requirements due to financial constraints, ageing infrastructure, and limited options for residual disposal. Therefore, effective water treatment technologies for SDWSs require the removal of multiple classes of water contaminants, low energy input, continuous operation with high efficiency in diverse water matrices, and the production of minimal residuals. Here, we propose to design a novel reactive electrochemical membrane (REM) system that is capable of 1) simultaneous adsorption and electrochemical oxidation/reduction of organic contaminants (e.g., disinfection byproducts), 2) inactivation of pathogens, and 3) electrochemical reduction of oxyanion contaminats (e.g., nitrate). The REMs are synthesized by the conversion of nonconductive TiO2 precursors to novel conductive Ti4O7 porous membrane materials. The objectives of the proposed work are: 1) to further improve the performance of the Ti4O7-based REM by adding carbon adsorptive materals to the membrane matrix and thus increasing trace level contaminant adsorption and subsequent electrochemical destruction; and 2) to validate the technical feasibility of using the novel REM for the removal of DBPs. The research is expected to provide important data that will demonstrate the feasibility of using the novel REM system as an effective treatment technology for the removal of multiple classes of contaminants in SDWSs.
Biological Denitrification for Small Water Systems Using Iron-Sulfur Minerals
Conventional technologies for treatment of NO3- contaminated source waters have high energy, chemical and waste brine disposal costs. Biological denitrification is a promising alternative; however, problems with undesirable by-products and complexity pose problems for small community water systems (CWS). A number of iron-sulfur minerals have the potential to support autotrophic denitrification including pyrite, ferrous sulfide, pyrrhotite, greigite, marcasite, troilite, mackinawite, pentlandite, and sphalerite. Based on our preliminary studies, advantages of biological denitrification using iron-sulfur minerals include: 1) the reaction can be carried out in simple upflow packed bed reactors (UPBRs) where the mineral serves as an electron donor and biofilm carrier, 2) little or no carry-over of dissolved organic carbon to the product water, 3) low excess biomass and sulfate by-product production and alkalinity consumption. The overall goal of the proposed project is to develop a biological denitrification process that uses iron-sulfur minerals as electron donors for small CWS applications. Microcosm studies will be used to compare a suite of iron-sulfur minerals as denitrification substrates. Bench-scale UPBR studies with selected minerals will be used to evaluate whether product water can meet drinking water standards. A preliminary economic analysis will be used to evaluate the proposed process for small CWS applications.
Removal of Nitrate from Groundwater without Co-Production of High Concentration of Disposable Brine
Principal Investigator: Arup K. SenGupta, PhD (Lehigh University)
The number of nitrate contaminated groundwater sites in the USA and around the world has increased rapidly due to the application of nitrogen-based fertilizers and subsequent biological oxidation. Anion exchange processes have been traditionally used for nitrate removal operations, where concentrated NaCl brine (10-20% NaCl) is the regenerant solution. But, disposal of high concentration brine containing nitrate has emerged as the most insurmountable problem confronting small- and medium-sized communities. Deep well injection, biological denitrification and catalytic denitrification provide opportunities to recycle the spent regenerant, but they all pose major hurdles and are not practiced routinely. Using representative contaminated groundwater, our laboratory research with a novel in series, two-bed ion exchange process demonstrated that use of brine can be eliminated altogether as a regenerant. Instead, at the end of every service cycle, carbon dioxide alone can be used as a regenerant, thus adding no additional electrolyte in the spent disposable regenerant. By eliminating high brine concentrations, the lower TDS regenerant waste could be treated in a septic tank in small communities or sent to a large wastewater treatment facility in larger communities. The two-bed ion exchange process is unique because the nitrate-selective anion exchanger in bicarbonate form precedes the weak-acid cation exchanger fibers in hydrogen form. Besides nitrate removal, the process achieves partial desalination, and can also remove fluoride or other co-contaminants. The key scientific finding of the research is that traditional commercial weak acid cation exchange resin beads are not amenable to regeneration with CO2 due to extremely slow, intraparticle diffusion-controlled kinetics. However, ion exchange fibers with very short diffusion path lengths (less than 50 μm), can overcome such shortcomings. Ion exchange fibers and similar materials are now available commercially. Thus, the technology can be rapidly implemented in the field or the existing nitrate removal systems can be retrofitted with minor difficulty. During the course of the proposed project, one small prototype two-bed system will be fabricated and tried both in the laboratory and the field. Development of a nitrate removal system, without being confronted with the spent regenerant disposal problem, is a major step forward towards sustainable treatment technology for small-medium sized communities.
Electrocoagulation and Electrooxidation to Treat Microbial and Chemical Contaminants in Small Drinking Water Systems
The proposed research will evaluate the efficacy of electrocoagulation and electrooxidation for the simultaneous mitigation of microbes, organic carbon (disinfection byproduct precursor) and trace organic compounds from drinking water. Electrocoagulation and electrooxidation will be tested independently as well as in tandem using surface and ground water, including both synthetic model waters and actual environmental waters. We hypothesize that electrocoagulation will be able to physically remove a large part of the bacterial and protozoan load as well as organic carbon, while subsequent electrooxidation will be effective as a polishing step to destroy the remaining pathogens and trace organic contaminants. Electrochemical water treatment technologies may be particularly amenable to small drinking water systems as they offer a number of advantages over conventional water treatment, including avoiding the addition of corrosive chemicals, easy operation and automation, no alkalinity consumption, small footprint, and portability for water treatment during emergencies and in remote settings.