A sand-anthracite filter or dual media filter/multi-media filter is primarily used for the removal of turbidity and suspended solids as low as 10-20 microns. Dual media filters provide very efficient particle removal under the conditions of high filtration rate. Inside a sand-anthracite filter is a layered bed of filter media.
Sand is used to remove the suspended particles and anthracite is used to remove the odor and color etc. to make the water fit for different applications. Gravels and pebbles are provided to support to both the media. Periodically, the sand-anthracite filter will backwash, which changes the water flow through the sand-anthracite filter.
Pressure sand filter is highly recommended for the removal of suspended solids & undissolved impurities like dust particles & heavy metals etc. doing so it reduces turbidity. Pressure Sand Filter is an ideal solution for the systems with high sediment, silt, sand, and turbidity. The sand filters are specially designed to take care of the range of suspended impurities.
Activated carbon (AC) is a natural material derived from bituminous coal, lignite, wood, coconut shell etc., activated by steam and other means, and each one have different adsorption properties (e.g. bituminous carbon for high chlorine reduction capacity).
Two of the most commonly occurring ions in natural waters are calcium and magnesium. Both are positively charged ions called cations, and each carries two unit charges. The presence of these two minerals in natural water causes “hardness”.
Problems associated with hard water can be minimized by using a water softener. Conventional softeners operate on the principle of ion exchange. The most common ion exchange method used today is the sodium cycle operation. In this process, calcium and magnesium ions are removed by exchanging places on an ion exchange resin with sodium. This process is commonly known as positive ion or cation exchange. Negatively charged ions from the source water remain. Softening does not reduce total dissolved solids; it exchanges the “troublesome” hardness ions for sodium ions.
Ultra filtration is a pressure-driven purification process in which water and low molecular weight substances permeate a membrane while particles, colloids, and macromolecules are retained. The primary removal mechanism is size exclusion, although the electrical charge and surface chemistry of the particles or membrane may affect the purification efficiency. Ultra filtration pore ratings range from approximately 1,000 to 500,000 daltons, thereby making UF more permeable than nano filtration (200 -- 1.000 daltons).
UF membranes are composed of a polymer, such as polysulfone or polyamide,that is usually extruded into flat sheets or hollow fibers or cut into disks as required by the specific application. A small disk of UF membrane may be subject to rapid fouling and produce a low flow rate for many processes. As a result, UF membranes are typically arranged in a configuration which maximizes surface area and reduces fouling by using a tangential flow design to reduce solute accumulation at the membrane surface.
RO is based on the process of osmosis. Osmosis involves the selective movement of water from one side of a membrane (a plastic film that looks similar to cellophane) to the other. To make the process work, pressure is applied to the contaminated water, forcing water through the membrane. Since contaminants do not move with the water as it moves across the membrane, purer water collects on the other side of the membrane. RO can reduce the amount of organics, inorganics, bacteria and particulates in water.