Water Project Team. Sanitation Overview

Transcription

1 Water Project Team Sanitation Overview

2 Defining the Need Sierra Leone diarrhea rate is 103 DALYs/1000; 103 years of productivity out of every 1000 is lost to the disease Highest ever recorded = 107 Water-borne diseases a major problem Bacteria/protozoal diarrhea; hep A/E; typhoid; shcistosomiasis (nonfatal, chronic parasite) Providing clean water immediately cuts infant mortality rate in half In Kono, water sanitation coverage was only 10% in Many people drink unsanitary water 1

3 Characterizing Water Quality Contaminants vary widely Microorganisms (bacteria that cause typhoid, etc) Solids Chemicals (arsenic, often from diamond mining) Fecal Matter in varying levels Water source is important Pump wells often safer; ground shields water from pollution Insufficient data on groundwater source quality and quantity Choosing a better water source should be considered before working to purify

4 Water Testing Many tests specific to a single microbe (E.Coli test)

5 Main Project Goals and Concerns Reliability is often more important than quality Cleaning time and cost Chemicals or complex materials? Scalability Consider improving well quality Potential for Multi-Step Treatment Can allow drawbacks of one treatment option to be circumvented through another

6 Filtration Methods Slow Sand Filtration Roughening Filters Rapid Sand Filters Diatomaceous Earth

7 Disinfection Methods Chemical Disinfection Ozone Solar Water Ultraviolet Disinfection

8 Slow Sand Filtration Combines several purification processes Settlement filtration, organism removal, chemical treatment Purification done by biological "schmutzdecke" at top layer Cleaning is very simple Requires only scraping off the top layer of sand; needed very infrequently Reduces bacteria levels significantly Requires low levels of suspended solids at inlet Pro: Cheap to construct; local materials; no chemicals Cons: May require a large system; potentially low flow rates; ineffective for a short time after cleaning 1.

9 Example System

10 Diatomaceous Earth Uses diatoms to create a thin filter layer Creates a cake of removed particles that must be backwashed Pro: Relatively cheap, can be scaled to small systems Con: Requires relatively clean water with no inorganic contaminants; requires a pressure or vacuum source

11 Rapid Sand Filters Pass water through activated charcoal and flocculation chemicals (aluminum) Pro: Removes very small particles; can be cleaned through back-flushing Con: May affect taste; potentially high maintenance; creates sludge; requires skilled supervision, regular backwashing; water cannot be too dirty at inlet

12 Microstrainers Fabric meshes of a stainless steel or polymer Fluid run by itself through mesh, or driven down pressure gradient using pump Pro: Removes large protozoa and algal cells Con: Often requires replacement when clogged; may require a pump; not particularly effective with smaller bacteria

13 Roughening Filters Pass water through increasingly finer gravel Removes 47% of bacteria Pro: Easy to build Con: Requires cleaning, backwashing

14 Chemical Disinfection Chemicals include COCl, ClO 2, NH 2 Pro: Proven ability to kill a variety of microbes Con: Alters taste; consumable; upkeep can be expensive; chemicals (chlorine) can be toxic in concentration, difficult to store or ship

15 Ozone Disinfection Generate ozone by passing air through electrical discharge, bubbling through water Pro: Kills majority of microbes; does not alter taste Con: Needs power source to generate ozone; must be continually generated; does not have any long-lasting disinfectant properties; more expensive than chlorination; ozone exhaust is toxic

16 Hydrogen Peroxide Apply measured dose of H 2 O 2 to the water Pro: Kills most microbes; does not alter taste Con: Short shelf life of H 2 O 2; high cost

17 Solar Water Disinfection Place water into PET containers, use sunlight to disinfect water Pro Kills most microbes Smaller scale; can be used as a supplement to other projects Completely free, using only sunlight Con: Requires 6 hours when sunny, 2 days when cloudy Difficult to scale up Requires PET containers Cloudy water must be pre-filtered

18 UV Purification Shine a special UV lamp on the water; kills organisms in the water Pro: Effectively destroys bacteria and viruses; requires only a short burst; completely nontoxic; easy to maintain Con: Does not prevent further growth of microorganisms; does not affect some microorganisms; doesn't affect highly turbid water; requires power

19 Other Concerns Take inspiration from "packaged plants" 1 Consider pilot testing to gauge effectiveness of various treatment options Consider both POE (point of entry) and POU (point of use) systems alongside centralized filtering Must consider disposal of byproducts for chemical, other means 1.

20 Overall Summary Methods used are highly dependent on the contaminants in the water Level of contamination Type of contamination (virus, bacteria, inorganic, etc) Many filtration methods involve consumable goods Many are dependent on cleaning and backwashing Must determine if the level of labor and technical skill required are viable Must balance filtering quality, speed, etc

21 Other Sources Systems-technologies.html