A THESIS SUBMITTED TO THE SCHOOL OF POST GRADUATE STUDIES OF ARBAMINCH UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENGINEERING IN WATER SUPPLY AND SANITATION ENGINEERINg

Abstract

Expensive conventional water treatment technologies were barrier for rural areas because they follow series of procedures with daily chemicals to get drinking water from impure water. The cheap technology called slow sand filtration is a proven and sustainable water treatment technology in rural communities. The objective of this research was to evaluate the pollutants removal efficiency of slow sand filter units from the synthetic water. For the achievement of this objective, four lab-scale filter columns were prepared from 4" Polyvinyl Chloride pipe with a 90cm bed depth based on the fluctuating sand characteristics of four setups. Each filter was adjusted to yield 20.75 l/day at a filtration rate of 0.1m/h and effective size (0.22mm), coefficient of uniformity (2.95), and coefficient of curvature (1.1) were used. The removal efficiencies of filters were in the range of turbidity (73.8–91.1%), feacal coliform (98.45–99.91%), total coliform (95.17– 100%), total suspended solids (88.2–99.2%), and total dissolved solids (36.5–41%). The first three filter's efficiency is affected by the total sand surface area, porosity, and hydraulic conductivity regarding turbidity and total suspended solids removal. Feacal coliform and total coliform removals depend mainly on biological activity in the filter cake that rapidly formed at the top of filter media due to less porosity. Slow sand filtration is simple to design, and operates. It had a heart full for the elimination of pollutants in water in a single-stage filtration without using chemicals and could be constructed by using locally available materials in rural areas. This is hopeful for use as an efficient water treatment system