CHAPTER ONE
INTRODUCTION
1.1   Background of the Study
Human waste or more technically referred to as ‘excreta’ is defined by Chamber’s Concise 20th Century Dictionary as “useless matter discharged by animal alimentary”, animals being humans in this context. Excreta is made up of a solid matter, feces, and a liquid matter, urine and is essentially an organic compound. The constituents making up the compound are carbon, nitrogen, phosphorous, sulphur and hydrogen. Also present are fats, carbohydrates, enzymes, proteins, trace elements, pathogens and many different bacteria.
Sewage is a type of wastewater that comprises domestic wastewater and is therefore contaminated with feces or urine from people's toilets, but the word sewage is also used to mean any type of waste water.Sewage is the physical infrastructure, including pipes, pumps, and screens, channels etc. used to convey sewage from its origin to the point of eventual treatment or disposal. Wastewater can come from (indicates likely inclusions or contaminants)
·           Human waste (feces, used toilet paper, urine or other bodily fluids) also known as black water usually from lavatories.
•            Cesspit leakage
•            Septic tank discharge
•            Sewage treatment plant discharge
•            Wasting water (personal, clothes, floors, dishes etc) also known as greywater or sludge.
•            The home Rainfall   collected   on   roofs,   yards,   hard-sandugsetc (generally clean with traces of oils and fuel).   
•            A Groundwater infiltrated into sewage.
•            Industrial waste.
•            Toxic waste (metal plating, cyanide production, pesticide manufacturing; etc)
The composition of wastewater varies widely. This is a partial list of what it may contain.
·        Water  (more than 95  percent),  which is  often  added during flushing to carry waste down a drain
·        Pathogens    such   as   bacteria,   viruses,   proteins   and parasitic worms.
·        Non pathogenic bacteria.
·        Organic   particles   such   as   feces,   hairs, food, vomit, paper, fibers, plant materials, humans etc,
·        Inorganic particles such as sand, grit, metal particles, ceramics, etc.
·        Gases    such    as   hydrogen    sulfide,    carbon    dioxide, methane etc.
·        Pharmaceuticals  and  hormones
1.1.2        Waste Water Quality Indicators
Anti-oxidizable material present in a natural waterway or in an industrial wastewater will be oxidized both by biochemical (bacterial) or chemical processes. The result is that the oxygen content of the water will be decreased. Basically, the reaction for biochemical oxidation may be written as.
Oxidizable material + bacteria +nutrient + O    CO2 +H20 +
Oxidized   inorganic   such   as   NO3   or   SO2.
Oxygen consumption by reducing chemicals such as sulfides and nitrites is typified as follows:
S2 + 202           SO42-
NO2- + I/202        NO3-