HIGHLY UNSAFE – Chlorine handled under pressure upto the point of dosing. Glass tube burst in the equipment due to pressure will lead to major chlorine leak.
NOT acknowledged by Bureau of Indian Standard (BIS) or any other international chlorine organization such as Chlorine Institute USA.
Since, chlorine gas is handled under pressure until the point of dosing, any normal leakage in gland/flange joints will be a potential hazard by nearly 10 times when compared to vacuum operated system.Hence operator safety is not ensured.
Due to pressure feed, chlorine gas will not dissolve in water to form a homogenous solution. Chlorine is best dissolved under VACUUM conditions. Undissolved Chlorinewill result in severe localized corrosion of pipeline incurring heavy maintenance costs
Water suck back into chlorinator due to creation of vacuum in chlorine line when the cylinder is empty. This will causecorrosion of chlorinator gas pipelines
Frequent replacement of system piping and equipment due to corrosion effect of Suckback water/ water vapour (moisture).
Water will be sucked back into tonners when tonner valve is not closed while reaching empty condition. This will result in corrosion of chlorine tonners / cylinders.
GRAVITY FEED CHLORINATION SYSTEM (ABSORPTION TOWER TYPE)
Chlorine gas is absorbed in packed tower by once through water flow. Chlorine absorption in water is not as efficient as in injector based vacuum chlorinator.
Suitable for place where there is intermittent power supply. Does not require power for operation.
Even though it is installed in remote water works such as gravity flow water supply system, it is not acknowledged by BIS.
Like pressure feed system, this also handles chlorine gas under pressure until point of absorption tower hence associated hazard of handling chlorine leak under pressure.
This system is a modified version of pressure feed system but suitable for only dosing chlorine in open channel, well etc.
Chlorine solution cannot be dosed in pressure main.
This system envisages dosing of purchased commerciallyavailable sodium hypochlorite (Naocl)
Very high operating cost, due to higher cost of sodium hypochlorite. Cost varies from Rs.4 to Rs.12/lit which can treat only 25 m3 (25000ltrs) @ 2 PPM dosage. For a 5 MLD plant operating cost will vary from Rs.800/day to Rs.2400/day depending on local chemical cost.
Highly Uneconomical, when compared to gas system whose operating cost will be only Rs.50/day.
Dependent on chemical supplier.
Chemical Inventory planning & co-ordination will become a major problem.
Sodium hypochlorite looses chlorine on storage due to its unstable nature. This leads to commercial loss when stored for a longer period.
Due to loss of chlorine on storage, exact chlorine dosage at the time of dose cannot be predicted.
Dosing pumps for dosing hypochlorite as susceptible to wear and tear leading to frequent breakdowns.
BLEACHING POWDER DOSING SYSTEMS
Bleaching powder being hygroscopic in nature, absorbs moisture from air and will become a pasty mass. Hence storage & handling is a difficult task.
Rapidly looses chlorine on storage. Leads to commercial loss on storage.
Due to rapidly depleting chlorine concentration in bleaching powder, exact chlorine dosage at the time of dosing is never known.
Bleaching powder solution preparation is a laborious process involving mixing, settling, decanting of clear chlorine solution, transferring to dosing equipment etc. If the solution has high residue, then lime willdeposit inside pipelines and equipment causing choking of lines and pumps.
Operating cost high when compared to chlorine gas systems. Considering average cost of bleaching powder as Rs.12/kg, which contains an average of 300 grams chlorine, can treat only 150 m3 of water. Hence chemical cost of treating 5 MLD water will be Rs.400/- against treatment cost Rs.50/- with chlorine gas.
VACUUM FEED – CHLORINATION SYSTEM
This system is used almost universally for more than 25 years.
International accepted practice of chlorination.
Acknowledged by BIS Code IS 10553 (Part I) 1983.
Safe method of chlorination.
Chlorine gas is handled under reduced pressure conditions immediately after gas source.
Chlorine gas is handled under vacuum until point of dosing hence any leakage in system will lead to only sucking air from atmosphere and not of chlorine leak into atmosphere.
Operator safety is inherent.
Vacuum feed technology mixes chlorine gas and water under vacuum condition at the injector.
Chlorine does not evolve from solution due to proper mixing & thorough dissolution.
Corrosion of piping and equipment avoided as chlorine thoroughly mixes with water and gets diluted to ppm level.
Operator can be trained to maintain the system easily.
While in operation, chlorine dosage can be easily varied from 1 to 10 ratios.
Highly economical – chemical cost will be only Rs.50 per 5 MLD of water.
Vacuum feed chlorinators will close in the absence of motive water failure thereby ensuring that chlorine is not dosed in the absence of water supply.
ONSITE-SODIUM HYPOCHLORITE GENERATING AND DOSING SYSTEMS
Latest proven technology.
Internationally accepted practice.
Highly safe because it generates only Sodium Hypochlorite that is chlorine in solution form.
Eliminates hazards related to chlorine gas based system.
Not dependent on chemical supplier since salt is commonly available.
Very economical to operate – since salt is the only raw material required.
Cost of operation will be only Rs.200/- for 5 MLD treatment @ 2 ppm dosage when compared to high cost of purchased chemicals.
Operation & Maintenance is very easy.
No skilled manpower required for O & M.
Sodium Hypo produced will be of 1-% concentration, which can be stored easily without much loss in chlorine.
Dosing system utilizes only pressure water for dosing solution and it does not require power for chlorine dosing.
Ideal for remote location where treatment/mobilization of chlorine cylinders or other chemicals are practically difficult.
Even though capital investment is slightly high for bigger water works; cost recovery can be achieved with in 3 to 4 years when compared to operating cost of sodium hypochlorite or bleaching powder plant.
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