Presentation on theme: "CalARP - Examination of Chemical Processes: Drinking Water Treatment"— Presentation transcript:
1CalARP - Examination of Chemical Processes: Drinking Water Treatment Presented by:Paul Beswick - MWDSC Environmental Support Services(213)CalCUPA Forum Annual Conference - 2/4/03
2PurposePresent an overview of drinking water treatment processes and chemicalsHighlight role of CalARP Regulated Substance(s) (RS) in water treatmentIdentify RS process risks and discuss risk mitigation measures
5TO DISTRIBUTION SYSTEM Typical Water Treatment PlantPRE-CHLORINATIONCl2Kills disease causing organisms and helps control taste-and-odor causing substances.DAFFILTRATIONFilters out remaining suspended particlesCLEARWELLProvides contact time for disinfection. Stores water for high demand.NH3CHLORAMINESKills disease causing organisms. Provides disinfectant residual for the distribution system.SEDIMENTATIONSettles out larger suspended particles.COAGULATION / FLOCCULATIONGathers together fine light particles to form larger particles (floc) to aid the sedimentation and filtration processes.FLASH MIXMixes chemicals with raw water containing fine particles that will not readily settle or filter out of the water.NaOHCORROSION CONTROLAdjusts the pH of the treated water to inhibit corrosion of pipelines.
6TO DISTRIBUTION SYSTEM Typical Water Treatment PlantFLASH MIXMixes chemicals with raw water containing fine particles that will not readily settle or filter out of the water.COAGULATION / FLOCCULATIONGathers together fine light particles to form larger particles (floc) to aid the sedimentation and filtration processes.SEDIMENTATIONSettles out larger suspended particles.Cl2NH3CHLORAMINESKills disease causing organisms. Provides disinfectant residual for the distribution system.PRE-CHLORINATIONCl2Kills disease causing organisms and helps control taste-and-odor causing substances.Cl2NaOHCORROSION CONTROLAdjusts the pH of the treated water to inhibit corrosion of pipelines.FILTRATIONFilters out remaining suspended particlesCLEARWELLProvides contact time for disinfection. Stores water for high demand.TO DISTRIBUTION SYSTEMDAF
7Coagulation/Flocculation The feeding and rapid mixing of one or more chemicals coagulants into the water, thereby beginning the formation of particles called floc.FLOCCULATIONThe gentle mixing of water and coagulants to form larger, heavier, more settleable floc.
8CoagulantsChemicals that consist of positively charged ions that neutralize the negative charges and promote coagulation.The most commonly used coagulants in water treatment are:Aluminum Sulfate (Alum) Al2(SO4)3Ferric Sulfate Fe2(SO4)3Ferric Chloride FeCl3
9Coagulant AidsAdded to improve coagulation; to build stronger, more settleable floc; to overcome temperature drops that slow coagulation; to reduce the amount of coagulant needed; and to reduce the amount of sludge produced.Common coagulant aids:Activated SilicaWeighting Agents (Bentonite clay)Polyelectrolytes (polymers)
10FiltrationThe major purpose of filtration is to remove suspended material (turbidity) from water.Suspended materials are removed when water passes through a bed of granular material known as the filter media.Turbidity removal is important for public health; it interferes with disinfection by shielding microorganisms from the disinfectant.
11Rapid Sand Vs High Rate Filter Media DUAL-MEDIATRI-MEDIAMediumSandCoarseCoalCoarseCoalMediumSandFine SandFine GarnetGravelGravelGravel
12The Chlorination Process Public Health benefits of chlorinationProcess flowProcess componentsChlorine safety/risk mitigation measures
13Chlorination Public Health Benefit A critical role protecting US drinking water supply from waterborne infectious diseases for over 90 yearsCholera, typhoid, dysentery, hepatitis A virtually eliminatedIn over 98% of disinfection systemsGermicidal potency, residual disinfection properties, efficiency, economy