“Structural performance of septic tanks constructed from clay bricks”

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“And they said to one another, ‘Come, let us make bricks, and burn them thoroughly’, and they had brick for stone, and bitumen for mortar - Genesis Chapt. 11 Vrs 3 (RSV) -- Holy Bible” The improper disposal of sewage matter has been particularly serious in the rural areas of the country. The problem has been equally serious in the urban areas. In the rural communities, people defecate into streams, gutters, backyards, rivers and bushes because of the non- availability of sewage disposal systems in their homes. Even in cases where they are available, the wastes from these systems are emptied into the above-mentioned media. This process pollutes the land, water bodies and the environment. Such waste contains pathogenic bacteria, viruses and protozoa that cause diseases such as typhoid fever, dysentery, cholera, gastro-enteritis and several parasitic infections. The pollution of water bodies also causes considerable harm to acquatic life. Inspite of the fact that the government , the various Metropolitan Authorities and Local Councils have promoted and encouraged the use of Kumasi Ventilated Improved Pit Latrine (KVIP) and the Septic Tank System for safe sewage disposal, many prospective landlords and communities have not been able to afford them. The reason has partly been due to the cost of the items. The cost has been relatively prohibitive to the target groups especially those in the rural areas due to materials that are used in the construction of the systems. The traditional materials used are mild steel reinforcement bars, concrete and sandcrete blocks. These materials are not readily available in the rural areas and where available, the cost is beyond the reach of the prospective landlords and communities. The main objective of this research is to explore into the possibility of using bricks in the construction of these sewage disposal plants with particular emphasis on the Septic Tank System. Bricks have been known to be .one of the earliest and most durable building materials known by man. The first massive structure to be built by man - the tower of Babel was built using burnt bricks as shown by the quotation at the beginning of this abstract. Elsewhere in the world, bricks have been used extensively in the construction of sewage disposal plants but its use has not been in vogue in Ghana. The raw materials for brick moulding - clay is reported to occur in huge deposits all over the country and is used extensively in the construction of dwelling houses. There is the hope that the use of bricks in the construction of these sewage disposal systems will go a long way to considerably reduce the cost of the facility thereby making it affordable to as many people as possible. The results of this research work indicate that unreinforced brickwork made from Ghanaian clays can be used for the safe construction of small Water and Septic Tanks for dwelling houses and there is the possibility of using reinforced brickwork for the construction of large ones for communities. Secondly sewage treated in brick tanks behave similarly as those treated in other tanks constructed from other materials and again, brick tanks did not deteriorate under the adverse conditions that prevailed in the septic tanks. Thirdly tanks constructed of brickwork are cheaper than those constructed of traditional materials like concrete and sandcrete block. Finally sun-dried brick tanks can only retain water and possibly sewage only when they are given thick render of rich mix. Sun dried bricks deteriorate rapidly when they come into direct contact with water and can therefore not be used for any meaningful structural work. It is believed that this research work will eventually help to make the facility available to as many Ghanaians as possible.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Philosophy in Civil Engineering, 1994