By Anjali B
Water supply is a basic need required for living creatures and human beings. Safe drinking water is essential to the health and welfare of a community, and water from all sources must have some form of purification before consumption.The method employed depends on the character of the raw water. One of the problems with treatment of surface water is the large seasonal variation in turbidity.
For many developing countries water treatment process involves coagulation, flocculation and sedimentation (which are the processes involved in removing turbidity from water) and disinfection are expensive processes because of the high costs involved and the difficulty in assessing the chemical coagulants including alum.Inorganic coagulants such as alum in combination with lime have been conventionally used for removal of turbidity from surface waters. The sludge formed from such treatment poses disposal problems because of its aluminium content and tend to accumulate in the environment and also because of large volume.Therefore, it is desirable that other cost effective and more environmentally acceptable alternative coagulants be developed to supplement if not replace alum, ferric salts and synthetic polymers. However, there have been studies on the use of indigenous natural coagulants. The use of locally grown and natural coagulants may result in a more sustainable and economically available alternative.
The history of the use of natural coagulants is long. Natural organic polymers have been used for more than 2000 years in India, Africa, and China as effective coagulants and coagulant aids at high water turbidities. They may be manufactured from plant seeds, leaves, and roots. These natural organic polymers are interesting because, comparative to the use of synthetic organic polymers containing acrylamide monomers, there is no human health danger and the cost of these natural coagulants would be less expensive than the conventional chemicals alike since it is locally available in most rural communities of Bangladesh. A number of effective coagulants from plant origin have been identified.
The need for simple, reliable and effective method of water treatment leads to the application of plant materials, including seed coagulants of Moringaoleifera. The Moringaoleifera tree grows in tropical and subtropical regions around the world and its seed have been used in drinking water treatment in small scale. Previous studies indicate that Moringaoleifera is an efficient coagulant for the removal of turbidity in both water and waste water treatment.
The Moringaoleifera is an alternative to the use of inorganic and synthetic coagulants.Disadvantages of inorganic and synthetic coagulants are it cause Alzheimer’s disease and similar health related problems, reduction of pH,high costs production of large sludge volume and low efficiency in coagulation of cold water. Moringaoleifera has potential in water treatment as a coagulant,a soften agent and bactericidal agent. Advantages of Moringaoleifera as a natural coagulant are its low cost,produces lesser volume of biodegradable sludge and it does not affect the pH of water.
Moringaoleifera seeds contain a coagulant protein that can be used either in drinking water clarification or wastewater treatment. It is said to be one of the most effective natural coagulants and the investigation on these kinds of water treatment agents is growing nowadays.
The Moringaoleifera is not used in field because of the some drawbacks of Moringaoleifera as it requires large amounts of seeds for small water treatment plant. Also the settling time is more. If the blended coagulant of Moringaoleifera& alum is used then the drawbacks of alum and Moringaoleifera is reduced and this blend coagulant gives best results, means it removes almost 99.4 % the turbidity. Heavy metals are also present in water which is hazardous to health. Moringaoleifera seed coagulant with double filtration also helps in the removal of heavy metals.