Defining Best and Worst- Case Bacterial Removals for a Home Water Treatment and Storage Unit

Transcription

1 Defining Best and Worst- Case Bacterial Removals for a Home Water Treatment and Storage Unit Gail Brion 1, Matt King 2 and Trish Coakley 1 1- University of Kentucky-ERTL; 2- TivaWater

2 The Problem Every day more than 3,000 children die from diarrhoeal diseases. Water, sanitation and hygiene has the potential to prevent at least 9.1% of the global disease burden and 6.3% of all deaths. 11% of the world s population 783 million people are still without access to safe drinking water. In rural areas in least developed countries, 97 out of every 100 people do not have piped water and 14% of the population drinks surface water for example, from rivers, ponds, or lakes. Household Water Treatment and Storage is a vital first step for many people. HWTS can provide the health benefits of safe drinking-water while progress is being made in improving water supply infrastructure Household-based interventions were about twice as effective in preventing diarrhoeal disease (47%) than improved wells, boreholes and communal stand pipes (27%) (Clasen 2006). The up-front cost of providing low-cost household water treatment is about half that of conventional source-based interventions. Most or all of that cost can be borne directly by the beneficiary, not the public sector. Sources: Progress on Drinking Water and Sanitation 2012, by the WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation, UNICEF Promotion of Household Water Treatment and Safe Storage in UNICEF WASH Programmes 2008.

3 One Solution: Home Water Treatment with TivaWater Bio-sand Filtration with Integrated Safe Storage.

4 Objectives of Research Determine the removal of a commercial, biosand type filter under optimal and worst case operational conditions to estimate the maximum and minimum health impacts that could be expected. Continuous, maximum flow rates, high head. Fast continual production when need is greater than 10-L day, or for commercial uses. Breakthrough conditions. Residence time in the filter is reduced to a few hours from several days. High fecal inputs. From waters with large fecal loads, like sewage contaminated rivers and streams.

5 Determine the Hydraulic Characteristics of the Filter. Maximum flow rate of 5.4 L/hour under constant, high head.

6 Find Appropriate Source Waters for Feeding Biofilm and Challenging Filter Challenge and feed water base was effluent from the secondary clarifier of the Town Branch Sewage Treatment Facility. Inlet sewage was added to base to boost the signal of E. coli in the challenge water. Target concentration of the challenge water 20,000 to 70,000 E. coli MPN/100 ml range (Quantitray). Each week had 3-4 challenges (10-36 L), with the other days the filter was fed (10 L).

7 Run Worst Case Scenario: High Head, High Constant Flow, 36-L Breakthrough Challenge. TIVA Filter Breakthrough Challenge Mode (36 L/day, grab sample at end of run) Date Liters Applied Percent Removal Note improvement as filter ripened. 7/15/ /16/ /17/ /21/ /22/2014* /23/ /31/ /7/ * sand leak ave removal 69.7 std dev 15.8 min removal 45.4 max removal 94.7

8 After Filter Ripening, Challenge with Recommended Overnight Filter Scenario: 10-L Challenge, Declining Head, Declining Flow Rate, Non-Breakthrough TIVA Filter Normal Use Challenge Mode (10 L/day, overnight hold, composite sample) Date Liters Applied Percent Removal 7/28/ /29/ /30/ /4/ /5/ /6/ Averaged 1.2 logs of removal ave removal 93.3 stdev 4.3 min 88.6 max 98.4

9 Filter Ripening and Operational Modes Makes Big Difference Tiva Filter Microbial Challenge with Ripening Breakthrough Challenge 36 L Applied (% Removed) Normal Usage Challenge 10 L Applied Overnight (% Removed) Pre-Ripened Removal (<282 Liters Applied) 60.8 Post-Ripened Removal (>332 Liters Applied)

10 Expected Health Benefits (DALYs by QMRA) Using the WHO QMRA Procedure Assuming pathogenic Campylobacter jejuni removal by TIVA biosand filter is well modeled by E. coli removals demonstrated in this project. Assuming the main route for fecal-oral transport of Campylobacter jejuni is the potable water source. Assuming there is only limited acquired immunity and 100% of the population is at risk. Campylobacter WHO Risk Assessment Assumed Concentrations (organisms/liter) Disability Adjusted Life Year per person per year* w/o treatment with TIVA, 10-L/day with TIVA, 36-L/day * WHO intermediate Target 10-4 DALY per person per year

11 Gains in Number of Productive Days for a Person or in a Community each Year Campylobacter WHO Risk Assessment Assumed Concentrations (organisms/liter) Days lost/year for a person w/o treatment with TIVA, 10-L/day with TIVA, 36-L/day Campylobacter WHO Risk Assessment Assumed Concentrations (organisms/liter) Days lost/year population of 100,000 w/o treatment 355,886 3,558,860 35,588,595 with TIVA, 10-L/day 23, ,444 2,384,436 Almost 25 million days regained with TIVA, 36-L/day 107,833 1,078,334 10,783,344

12 Summary Biosand filters can produce more than 1-log of removal after ripening and with extended time in filter. Testing must include different flow and use regimes to determine best and worst case removals. Use of these filters, while not meeting the 4-log removal desired, can be expected to have a measurable impact on the health status of households and communities. Less sickness means more human-power for other enriching activities. (3x less illness even under high head, high flow, overproduction conditions with heavily polluted water) Source water quality must be considered when using these types of filters w/o disinfection. Training in the correct use, and potential abuse, of the filters is important. People are likely to subject filters to overuse flow conditions to maximize production.

13 We wish to thank TivaWater for allowing us access to their filter prototype and for their open collaboration. Not all companies would allow worst case results to be shared, but they wanted others to be able to follow the approach we designed. We wish to acknowledge John May of the Environmental Training and Education Laboratories for his assistance with this project.