International Journal of Engineering Science Invention ISSN (Online): 2319 – 6734, ISSN (Print): 2319 – 6726 www.ijesi.org Volume 3 Issue 11 ǁ November 2014 ǁ PP.25-36 www.ijesi.org 25 | Page Design of a water treatment Mechanical Mixer for a pre- chlorination tank as an effective algae control, aeration and coagulation processing. 1, H. A. Abdulkareem , 2, S. B. Abdurrahman , 3, Isyaku Umar 1, Department of Mechanical Engineering College of Engineering Kaduna Polytechnic and Applied Science Department College of Science and Technology Kaduna Polytechnic ABSTRACT : In any water treatment plant particularly in the rural communities, the provision of potable water supply system is a difficult task due to unavailability of sustainable power supply system. A mechanically operated mixer for pre-chlorination tank is a major pre-requisite in such a system. The design of a mechanically operated mixer has been successfully carried out leading to an efficient control of algae, aeration and coagulation process which is capable of storing potable water for a period of 3.7 hour for small rural community in Borno State, Nigeria in the event of failure of the pumping system. KEY WORDS: Mixer, Pre-chlorination, algae, aeration, coagulation I. INTRODUCTION A treatment plant consists of many processes, which can generally be subdivided into pre-treatment, and treatment. Some of these include screening, coagulation, flocculation, filtration etc. The impurities are removed in order of size, the bigger ones being eliminated first. Since, not every water requires all the treatment process (Smsrthurst G.:1979). The impurities are mainly removed by the following process: Floating objects by screening; Algae (if possible) by straining; Excessive iron, Manganese and hardness in solution by precipitation in basins after the addition of chemicals; This can generally be outlined as; screening; raw-water storage; pre- chlorination; aeration; algae control; straining; preliminary setting; mixing; coagulations; flocculation; settlement, filtration and sterilization. our interest here is to come up with an optimum design for a mechanical control mixer for effective algae control, aeration and coagulation process II. PRE-CHLORINATION Pre-chlorination refers to the practice of injecting chlorine into the raw water soon after it is obstructed from the river. This is usually omitted on water of reasonable quality (low bacteria count). Usually 2-5mg/1 are commonly used. This oxidizes and precipitates such as irons and manganese and kills algae and bacteria.A drawback to using pre-chlorination is that raw water has a high chlorine demand and much greater quantities of chlorine are observed than in later chlorination to affect the same degree of sterilization. It should be regarded as a substitute for post chlorination however; it is essentially an additional safeguard to be adopted only when extremely polluted (but clear) raw water has to be used. (Smsrthurst G.:1979) AERATION :This treatment process provides oxygen from the atmosphere to effect beneficial changes in the raw water. At the same time it may liberate undesirable gases such as carbon dioxide, hydrogen sulphide. The principle behind this is mixing the raw water with normal air from the atmosphere to replenish or add to the raw water quality. This trend generally improves the water taste, odor, and color and may also affect the killing of some pathogens. This is usually done by splashing the water over trays to break up the stream into countless droplets or by reversing the effect and blowing air bubbles through the water.Gases are absorbed or liberated from, water until equilibrium is reached between the natural content of each gas in there and its content in the water. (Smsrthurst G.:1979) Aerators are commonly found to be necessary if any of the following conditions are present in the raw water. a. Hydrogen sulphide (tests, odor etc.); b. Carbon dioxide (corrosive tendencies); c. Test due to algal growth (caused by volatile oils release); d. Iron and Manganese in solution; e. De-aeration f. Above increase oxygen content, while (a) – (b) liberate excess gas (Smsrthurst G.:1979).