Safe drinking water is very important for human beings. Human life has been under threat in many parts of the world because of high arsenic contamination in ground water. Arsenic is tasteless, colourless and odourless even if its concentration is very high in water. Health effects start to emerge after a long time use of arsenic contaminated water making the problem more serious. So many methods have been tried to get rid of arsenic problem. But these methods have been showing complexities and inefficiency resulting from use of chemicals, careful control of pH, sludge handling, bacteriological growth, requirement of expertise for proper operation etc. Moreover, implementation of a technique or method only for removal of arsenic is not feasible in most cases. The HVR house-hold water purifier, which is based on membrane distillation process, and the reverse osmosis purifier which are based on membrane filteration is an effective tool for production of pure drinking water. It can effectively remove all non-volatile impurities including arsenic from water.

Introduction :

Membrane filtration is a technique which is used to separate particles from a liquid for the purpose of purifying it.This filtration method has a number of applications, ranging from treating wastewater to filtering milk used for cheese production, and there are several different approaches to membrane filtration. In all cases, the goal is to create a filtered solvent. A number of different types of systems are available from companies which specialize in filtration products, along with replacement membranes and other parts and equipment.

In membrane filtration, a solvent is passed through a semi-permeable membrane. The membrane's permeability is determined by the size of the pores in the membrane, and it will act as a barrier to particles which are larger than the pores, while the rest of the solvent can pass freely through the membrane. The result is a cleaned and filtered fluid on one side of the membrane, with the removed solute on the other side. In all cases, the size of the pores has to be carefully calculated to exclude undesirable particles, and the size of the membrane has to be designed for optimal operating efficiency. Membranes are also prone to clogging as the pores slowly fill with trapped particles, which means that the system must provide accommodations for easy cleaning and maintenance so that it can be kept in good working order Many membrane filtration systems are designed for industrial uses. One of the big advantages to such a system is that it does not require the use of chemicals or additives, which cuts down on operating costs. Additionally, it requires minimal energy, and it can in fact be designed to run on almost no energy, with a pressurized system which takes advantage of gravity and forces the solvent through the membrane at a steady rate.

Arsenic :

Arsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in many minerals, usually in conjunction with sulphur and metals, and also as a pure elemental crystal. Arsenic is a metalloid. It can exist in various allotropes, although only the grey form has important use in industry. The main use of metallic arsenic is for strengthening alloys of copper and especially lead (for example, in car batteries). Arsenic is a common n-type dopant in semiconductor electronic devices, and theoptoelectronic compound gallium arsenide is the most common semiconductor in use after doped silicon. Arsenic and its compounds, especially the trioxide,are used in the production of pesticides, treated wood products, herbicides, and insecticides. These applications are declining, however. Arsenic is notoriously poisonous to multicellular life, although a few species of bacteria are able to usearsenic compounds as respiratory metabolites. Arsenic contamination of groundwater is a problem that affects millions of people across the world.