2015 Progress Report: Improving Drinking Water Quality for Small Rural Communities in MissouriEPA Grant Number: R835173
Title: Improving Drinking Water Quality for Small Rural Communities in Missouri
Investigators: Yang, John , Hua, Bin , Inniss, Enos , Shi, Honglan
Institution: Lincoln University-MO , University of Missouri - Columbia
EPA Project Officer: Page, Angela
Project Period: December 1, 2011 through November 30, 2016
Project Period Covered by this Report: December 1, 2014 through November 30,2015
Project Amount: $499,996
RFA: Research and Demonstration of Innovative Drinking Water Treatment Technologies in Small Systems (2011) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
The overall goal of this project is to improve drinking water quality for small rural communities in Missouri, with objectives of identifying water quality issues in three selected small drinking water systems and developing cost-effective treatment technology that addresses the identified water problems. The project has been granted a 1-year, no-cost extension this year, with project expiration on 11/30/2015. The major tasks focused this year are to: (1) continue to characterize the source water and drinking water in the three selected treatment systems and identify water quality issues facing the small rural communities; (2) develop novel treatment technologies to improve the water quality problems identified for each small water system based on the cause and realistic conditions of each water system; and (3) conduct pilot test studies of the developed technologies in the selected small water systems.
In an effort to address the problem of high trihalomethane (THM) formation resulting from the high ammonia source water of small water system, three treatment technologies or strategies are being developed: (1) Alternative disinfectant of peracetic acid (PAA) was tested for disinfection efficiency and reduction of disinfection biproducts (DBPs, THMs, haloacetic acids, and bromate) formations under various conditions of dosages, pHs, contact times. The results indicated that PAA is an effective disinfectant that results in no significant DBPs formation under the tested conditions;( 2) Ammonia removal was studied using various adsorbents. Zeolite was found effective to remove ammonia from source water and lower chlorine dosage needed for disinfection, consequently reducing the DBP formation; (3) A change of water treatment processes was proposed to reduce DBPs formation. Original treatment method was to add a large amount of chlorine during the lime softening/coagulation process to reach breakpoint chlorination for ammonia removal, which resulted in high THM (TTHM > 80 ug/L) due to the high chlorine usage and long contact time. Two treatment adjustments were suggested. The first change was to add chlorine at the later step of the treatment for ammonia removal (at the re-carbonation step), which could decrease the contact time. This suggested change was found significantly lowering chlorine demand by one-third (~1/3) and resulting in a significant decrease of THMs (< 60 ug/L) content. To further reduce THM formation in the distribution system, the second suggested change was to use chloramine as residual disinfectant in finished drinking water. Those changes would lead the system using high ammonia source water in compliance with EPA current drinking water DBP regulation.
To address the concern of elevated total organic carbon (TOC) in source water for the selected water system, several treatment approaches are currently being investigated for the TOC removal efficacy. The change of the treatment process using different types of activated carbon, such as coal-based vs. coconut-based carbons is being tested. A discussion with the facility manager also included consideration of separation of the carbon and coagulant injection locations. The carbon baffle walls also have been designed and fabricated for a bench scale testing. In addition, bench-scale experiments have been conducted to investigate the efficacy of TOC removal and reduction of disinfection by-product (DBP) formation by advanced chemical oxidation using hydrogen peroxide and ferrous iron. Several operation parameters including pH, H2O2 and Fe2+ concentration, reaction time are being evaluated, to achieve the maximum efficiency. Preliminary results of this study indicated that the removal of DBP precursor by the advanced chemical oxidation was fast and reached a steady state in less than one hour under the pH range of drinking water treatment.
Six graduate students and four undergraduate students majoring in environmental science or engineering or analytical chemistry have been fully or partially supported by this project and trained for research skills and experiential learning experience on three universities’ campus, respectively. The students are working on various aspects of proposed research activities, including site sampling, chemical or instrumental analysis, literature review, experimental design/ implementation, data collecting, processing, reporting, manuscript preparation, and conference presentation. One of the graduate students completed a Master degree thesis entitled “Sedimentation Enhancement by Fabric Inclined Settling Screen to Decrease Disinfection By-Products Formation Potential” in May 2014 as a part of research effort on the screen technology pilot study.
a. Finish the laboratory experiments to characterize the performance of the activated carbon baffle walls for dissolved organic carbon removal, in efforts to effectively reduce DBP formation potential.
b. Construct and test pilot unit for activated carbon baffle walls at our partner facilities
c. Complete the bench-scale experiments of advanced chemical oxidation for TOC removal and reduction of DBP formation.
d. Assess the water qualities upon the new technology implementation in the small water systems or pilot scale treatment.
e. Technology transfer and operator trainings.
f. Prepare, submit and publish manuscripts.
g. Draft and submit a final project report.