The feed water, depending on its source, may contain various concentrations and sizes of suspended solids and dissolved matter. The objective of the feed water pre-treatment process is to improve the quality of the feed water to the level which would result in reliable operation of downstream equipment. Depending on the treatment requirements, pre-treatment systems are designed to get rid of troublesome impurities first. Fine suspended solids, colloids or silt can be removed by coagulation method where as some sparingly soluble salts such as fluoride, silica, iron etc can be removed by chemical precipitation method in Pretreatment plants. Marcuras provides following processes to make feed water suitable for the downstream processes:
- Tube Settlers /Lamella Clarifiers
- HRSCC / Clarifiers / Clari-Flocculators
- Dosing Systems
- Flash Mixers
- Static Mixers
These clarifiers settle the suspended matter from pre-flocculated water or effluent. The clarifiers are constructed in Metal as well as RCC depending on the size and are equipped with scrapers, scraper drives, stationary or moving bridge, collecting launders, wear plates, V-notch boxes etc.
A variant in this equipment called Clari-flocculator combines flocculation zone along with the conventional clarifier mechanism. This eliminates the need of having a separate equipment for flocculation. The settling is aided by virtue of gravity with carefully designed hydraulic flows and the sludge blanket formed with TSS also traps finer particles to provide clear water at the outlet.
Commonly known as HRSCC, these are next generation technologies that achieve higher throughput in a smaller footprint than conventional clarifiers – resulting in cost savings and improved performance. The sludge formed in the settling process is re-introduced to feed water so that the process of floc formation is better. HRSCC suits best for varying or even low turbidity loads and optimizes the chemical costs.
The design features of the solids contact type clarifier provide the three zones necessary for proper clarification:
- Rapid mix zone, where raw water, recirculated precipitates and fresh reagents are rapidly mixed together.
- Slow mix zone or flocculation zone, where gentle mixing permits floc formation and brings the floc into intimate contact with the suspended impurities.
- Clarification or settling cone, where the upward flow (rise rate) is reduced to a low value to permit the precipitation to settle out.
This ensures a higher clarified water quality and greater tolerance to variations in inlet conditions. Marcuras is involved in producing HRSCC, which is very reliable and cost-effective.
- Tube Settler
- Plate (Lamella) Settler
Both these devices use the principle of high surface contact area and countering upward velocity with inclination of surface. The specific angle (60 0) results in lowering the upward velocity of particle thereby allowing higher rise rates and lower cross-sectional area. Plates and Tubes used in these devices are available in various lengths, profiles and MOCs to suit specific applications.
Marcuras is engaged in design, manufacturing and supply of Inclined plate (lamella) clarifiers, tube settlers, which are based on innovative technologies that increase basin settling area by creating an inclined settling surface. Overall plant footprint can be reduced substantially using these technologies.
Flocculators are used as preceding equipment to settling devices such as clarifiers or settlers. The main function of floculator is to allow contact of flocculated particles with each other to form a larger floc which is easier to settle or trap than individual small particles. Floculators can be used for making flocs of suspended solids as well as chemical precipitates. This equipment allows time for reaction and to allow particles to come in contact with each other with slow speed agitation. These can be constructed in metal as well as RCC and are equipped with floculator shaft, blades and drives.
Other Supplementary Equipment
Dosing System : Dosing systems are provided to dose chemicals, coagulants, flocculants required for reactions. The systems consist of Dosing pumps of different types and MOCs, Dosing Tanks, Agitator and mounting skids.
Flash Mixers : Flash mixers are used for rapid mixing of chemicals before flocculation and are usually high speed mixers with a small retention tanks.
Static Mixers : Sometimes, depending on the nature and criticality of process, inline static mixers can be used for mixing chemicals for rapid reaction. These are inline devices with internal baffle construction to increase turbulence for chemical mixing. Obviously there is no running cost as there are no electrical or moving parts.
A water filter removes impurities from water by means of a fine physical barrier from a chemical process or a biological process. Filters can be used for suspended solids removal, removal of organics, odour, oil& grease, iron etc by selecting the right type of medium for filtration. We offer a wide range of water filtration systems that provide you clean & healthy water to use. Designed to meet the stringent requirements of clients these include. The entire ranges of filter are available in different MOC like FRP, MS, MSRL, SS etc. They are available in fully automatic, remotely operated, manually operated or with multiport valves.
Our filters work on the principal of depth filtration. The principal media in these filters is quartz grade sand and anthracite. Other supporting media include pebbles of various sizes, crushed gravel and silex. The major advantage of this kind of filters is that anthracite which provides for coarse filtration is lighter than filtering sand. Due to which one stage of coarse filtration takes place on the anthracite bed and the next stage takes place on the sand bed. Thus, depth filtration is achieved. Since both media (viz sand and anthracite) are employed the dirt loading capacity of these filters is twice that of pressure sand filters. Hence these type of filters are more capable and give high performance.
The principal media in these filters is activated carbon. Other supporting media include pebbles of various sizes, crushed gravel and silex. The activated carbon is a highly porous media. This property of carbon allows it to adsorb the free chlorine in raw water. Also organic matter present in colloidal form, oil & grease is adsorbed in these pores. Thus odour emanating from raw water on account of these colloids is reduced. The activated carbon present in the standard range has an iodine value of 450. This carbon is also available in iodine values of 600, 900 and 1200.
The principal media in these filters is manganese dioxide. Other supporting media include pebbles of various sizes, crushed gravel and silex. Manganese dioxide catalyses precipitation of iron and holds back the precipitated matter on the filter bed. These are used to remove iron from ground waters.
For larger flow rates where pumping is a constraint, we suggest gravity filter, also known as rapid sand filters, usually at the outlet of pretreatment plant. This reduces pumping requirement and can be a good choice where space availability is not a constraint. AVGF is a boon for places which are remotely located where operators can not attend on regular basis. Automatic Valve-less Gravity Filter comes with a unique feature of initiating backwash based on pressure drop and it does not involve any automation product such as auto-valves, controllers, PLCs etc. It operates on gravity and backwashes purely on delta-P using simple hydraulic principles. AVGFs are Ideally suited for village water supply schemes and remote locations.