Sewage Treatment 2017 Chapter one 1. INTRODUCTION TO WASTEWATER TREATMENT 1.1. Systems of Sanitation The waste products of a society including the human excreta had been collected, carried and disposed of manually to a safe point of disposal, by the sweepers, since time immemorial. This primitive method of collecting and disposing of the society's wastes has now been modernized and replaced by a system, in which these wastes are mixed with sufficient quantity of water and carried through closed conduits under the conditions of gravity flow. This mixture of water and waste products, popularly called sewage, thus automatically flows up to a place, from where it is disposed of, after giving it suitable treatments; thus avoiding the carriage of wastes on heads or carts. The treated sewage effluents may be disposed of either in a running body of water, such as a stream, or may be used for irrigating crops. The modern water-carried sewerage system is preferred to the old. Conservancy system, because of its following advantages: (i) The water carriage system is more hygienic, because in this system, the society's wastes have not to be collected and carried in buckets or carts, as is required to be done in the conservancy system. (ii) In the conservancy system, the waste products are generally buried underground, which may sometimes pollute the city's water supplies, if the water supply pipes happen to pass through such areas or the wells happen to draw water through such areas. (iii) In the conservancy system of sanitation, the entire day's human feces are collected and then disposed of in the morning, once a day, thus, from this type of latrines, pungent smells may continue to pollute the surroundings for the entire day. But since in the water, carried system, the human excreta is washed away as soon as it is produced, no such bad smells are produced. Moreover, in the conservancy system of sanitation, the waste waters from bath rooms, wash basins, kitchen sinks, etc. ; is carried through open road side drains, as this is supposed to be not Ambo university Page 1 Prepared by Biniyam T