Design slow sand filtration unit Assignment Example | Topics and Well Written Essays - 5000 words

Design slow sand filtration unit - Assignment Example Disinfection It is any process that deactivates, removes contaminants or kills pathogens that may be present in water. It is usually the last step in the household water treatment process and comes after sedimentation and filtration. Effective size This refers to the size opening read from the grain size distribution graph that will only pass 10% of the sand. Hygiene Various practices, for example hand washing, which help ensure both cleanliness and good health. Filtration It is the process of allowing water to flow (pass) through the layers of a porous material, such as sand, with the aim of removing pathogens and any suspended solids. It is carried out as the second step in the household water disinfection and treatment process and comes after sedimentation and before the disinfection process. Flow rate It is the time taken to fill a certain container of water, most often a one litre container. It is measured once the slow sand filter is fully filled with water. Nutrient This refer s to any that is used by microorganisms for both survival and growth. Although this term is applied to refer to phosphorous and nitrogen in contaminated water, it can also be used to describe other chemicals. Pathogen This term refers to any disease causing living organism. The pathogens that are most commonly found in water are protozoa, bacteria, viruses and helminthes. Pores These are the small spaces between the grains of sand that allow water to pass through them. Sanitation It is maintaining clean and hygienic conditions that ensure prevention of diseases through services like garbage collection and proper waste disposal. Sedimentation It is the process used in settling out solids and particles that are suspended in water under the influence of gravity. Suspended solids These are small solid particles that fall in water and thereby causing turbidity. They are removed through the sedimentation or filtration process. Turbidity Turbidity is caused by the suspended solids that flo at in water such as sand, clay and silt. It is used to refer to the quantity of light that is reflected off these particles suspended in the water and which make the water look dirty or cloudy. It is measured in Nephelometric Turbidity Units (NTU). Uniformity coefficient It is a measure of how poorly or well sorted the sand is. It is the size of opening that is read from the grain size distribution graph that will allow pass of 60% of the sand divided by the size opening that will allow passing of 10% of the sand. Water quality Refers to the physical, chemical and microbiological characteristics of water. The level of the quality of the water to be used varies depending on the purpose for which it is intended. Wet harrowing This is a technique used in cleaning slow sand water filters whereby the sand surface is agitated gently in order to stir up the bio layer. The cloudy water is then drained off and then afterwards, the filter is allowed to operate for a number of days in order to re-establish the bio layer. Abstract Also known as a bio sand filter, slow sand filters have been used as a technique of water filtration since the nineteenth century. The most widely used version of slow sand filters used is constructed using concrete and has a height of 95 cm and a width of 36 cm and with a flow rate of 20-40 liters per hour. There are over 80, 000 filters used in 36 countries. There are various modifications which