Water Treatment Plant

Description

DESCRIPTION OF TREATMENT REQUIRED FOR DRINKING WATER TREATMENT PLANT 1. Raw Water Storage & Supply The raw water having silt and suspended solids is supplied by client at inlet of water treatment plant. After checking water quality available for treatment, systems are designed. In case of treatment required for river / canal / lake water which are contaminated with high turbidity and floating impurities, the following steps are being considered under designing. 2. Pre Filtration The raw water having silt and suspended solids is passed through 1000 micron rating micron filter and then through 500 micron rating filter. The particle size above 500 microns retained in the pre-filters. These filters are fabricated from stainless steel 304 sheets with stainless steel strainers, quick opening type, complete with inlet/outlet/drain valves and pressure gauge assembly. This systems are normally installed at intake well or at the source of water. 3. Pre-aeration System The raw water after pre-filtration will be pumped and taken to a tank called cascade aerator for aeration of water to remove carbon dioxide and organics. Other systems are also available for small capacity plants where air will be supplied through twin lobe type air blowers for aeration of water to remove carbon dioxide and organics. 4. Coagulation and Settling Process The raw water after pre-aeration shall be taken to a flash mixing chamber where chemicals like alum or poly aluminum chloride and lime will be dozed at desired calculated level (doze of chemicals is calculated on the basis of inlet turbidity load and through jar test apparatus. Suitable Flash Mixer are installed on flash mixing chamber for rapid mix. Underflow will be taken to Flocculation Chamber of Clarifier or separate tank with low speed flocculators are installed The chemicals once mixed with water coagulate the turbidity and make big flocs which are settle able. The flocculated impurities in the water will be taken to clarifiers or settling tank (plate settler design) where settle able solids in form of sludge settle down at bottom and clear water containing turbidity not more than 20 NTU over flow to collection tank or directly to filter beds. In RCC Clarifiers, provision of scrapper mechanism shall be provided either Central Drive or Peripheral type depending on diameter of RCC Circular Clarifier. 5. Filtration The clarified water stored in collection tank then pass through the beds of rapid sand gravity filters or through pressure sand filters for removal of remaining turbidity or suspended solids. Backwash Arrangement: The backwash of rapid gravity sand filters are carried out through air securing at first stage which help loosening of sand bed & backwashing at second stage through overhead clear water tank from where water flow through under beds of filter beds in upward direction and remove all settled mud or turbidity to drain. 6. Chlorination For disinfection purpose and to make water free from harmful bacteria, post chlorination shall be given to filtered water. There are dosing systems available for disinfection like pressure feed gas chlorination, water base liquid chlorine solution or bleaching powder