NCER Assistance Agreement Final Report Executive Summary

Date of Final Report: April 6, 2007 EPA Agreement Number: Project Title: Sustainable Concrete Filtration System for Developing Communities Faculty Advisors: Dr. Stephan A. Durham and Dr. Anu Ramaswami, Department: Civil Engineering Institution: University of Colorado at Denver and Health Sciences Center Student team member: Gregory M. Majersky, Civil Engineering Project period: August 1, 2006 to July 31, 2007 Description It was the goal of the study team to develop a system that can filter contaminated water; thus producing safe drinking water for developing communities. The University of Colorado at Denver and Health Sciences Center, UCDHSC, P3 team evaluated a non-conventional filter material. Permeable or pervious concrete has traditionally been used in producing pavement structures. Pervious concrete is a hardened mixture comprised of water, cement, and gravel. The mixture has little to no sand. With the absence of sand, voids are present to allow water to flow through the concrete structure. Our goal is to design the shape, size, and effective gravel size to successfully filter contaminates from non-potable water. The research team chose concrete due to its wide use and availability throughout the world. Global experience in working with this material is present and sufficient supply and production infrastructure are already in place. No additional energy is required to create systems to produce this traditional material. Objective The objectives of this research are:

To demonstrate that pervious concrete filters can be fabricated as regular concrete but without fine grained materials. The ease and simplicity in fabrication of these samples does not require special training and special fabrication materials.

To examine the pervious concrete filter effectiveness in improving overall water quality for consumption or other uses.

To investigate the hypothesis that eliminating gravel larger than x inches is more effective in bacteria and inorganic compound removal than an unsieved composition of coarse grains when the filter dimensions were identical.

The overall goal is to provide people in developing communities, without any need for electrical power, chemicals or expensive new technology and at minimal cost clean drinking water. In addition, an existing technology, permeable concrete, is being evaluated for a new potential use.

Summary of Findings The first test performed was an erosion test. This was to examine how much, if any, cementitious material or aggregate would be physically removed by the presence of flowing water. Initially, the first three tests produced slightly turbid water with a small amount of pebbles. As a result of this test, the research team began to flush the filter with cold tap water for 70 minutes at a flow rate of 1 L/hr. Laboratory analysis of samples taken from the erosion test was measured for metals concentrations and pH with an Inductively Coupled Plasma (ICP) instrument. The erosion test samples were analyzed for total recoverable metals, with the primary focus being iron, aluminum, and magnesium. Three samples experienced higher than expected levels of magnesium. Results showed that both iron and aluminum concentrations were within the Environmental Protection Agency (EPA) secondary maximum concentration limits (MCLs) for drinking water. Bacterial testing was performed on filters with sieved and unsieved coarse aggregate. These tests were conducted to provide a comparison of filter performance between the unsieved vs. sieved filters. Pre-filtration and post-filtration dissolved oxygen (DO) measurements were taken to measure oxygenation abilities of the unsieved and sieved filters. The sieved filter produced an average of 0.21 mg/L increase in D.O. levels over the unsieved filter. Percent removal of bacteria was calculated on a mg of bacteria/L basis. The filter was successful in removing bacteria from a concentration of about 10^8 bacterial per mL of water to less than 1 per mL. The percentage of bacterial removal for both filters was well in excess of the EPA primary MCLs for bacteria (99.9%). The results of the metals analysis found that iron was removed to less than the minimum detection level of the ICP in all but the third trial. The concentration of iron in both cases was in excess of the EPA’s secondary drinking water standard of 0.3 mg/L. The percentage of sodium removed by both filters increased similarly with each successive trial.

Lastly, post-filtration pH was measured for each sample. The range of pH was 11.45 to 12.52. This level of pH is extremely high and is a concern regarding the filter’s effectiveness. The pH level of filtered water will be further investigated in Phase II. Conclusions This study discusses a potentially new method of providing potable water to people in developing communities without adequate drinking water. Concrete is a recyclable material providing for both environmental and economical benefits. Infrastructure is already in place around the world to produce concrete, thus little or no additional effort is needed to produce pervious concrete filters. The filter was determined to be effective in filtering bacterial; however, concentrations of other chemical contaminants may increase in concentration. This was particularly evident with the pH level of the filtered water. These concerns will be further investigated in Phase II.

The unsuccessful factors of this experiment were an unexplainable increase in dissolved copper concentrations (from 2 to 9 mg/L) and a very high pH (11 to 12). Further testing will be conducted to evaluate copper concentrations and removal using this type of filter. The impact of this project is the goal to provide cleaner water, which has an enormous impact on the quality of life for all life on this planet. Phase I of this study focused on the application of an original and innovative idea applied to an existing product, resulting in a new use for pervious concrete. Proposed Phase II Objectives and Strategies Phase I of the pervious concrete filter study provided the P3 team with a prototype design and preliminary filtration results. The proposed Phase II study will investigate the high pH levels, low percent removal of copper, and high levels of magnesium in water quality testing conducted in Phase I. In addition, the team will test additional contaminants not included in the Phase I scope of work. The proposed study which includes the analysis and modeling of permeable concrete filters for a developing community consists of five tasks. These tasks include:

Task 1 – Travel to a developing community to understand the need, capabilities, and resources needed to fabricate and install pervious filters for potable water supply

Task 2 – Examine and fabricate additional pervious filters Task 3 – Perform water quality testing on old and new filters Task 4 – Model the “on-site” fabrication and installation of a filter in the

laboratory Task 5 – Data analysis and development of pervious concrete filter guidelines

Supplemental Keywords: water, drinking water treatment, bacterial contamination, disinfection, sustainable development, permeable concrete, pervious concrete