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Treating Water and Wastewater with Lime

Treating Water and Wastewater with Lime. Kentucky Water and Waste Water Operators Show. NaOH. Ca(OH). Na CO. 2. 3. 2. 175. 150. CaO. CaO  MgO. 125. 100. WEIGHT OF 100% ALKALI. 75. 50. 25. 0. 75. 100. 150. 25. 50. 125. 175. 250. 200. 225. 0. SULFURIC ACID. 175.

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Treating Water and Wastewater with Lime

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  1. Treating Water and Wastewaterwith Lime Kentucky Water and Waste Water Operators Show

  2. NaOH Ca(OH) Na CO 2 3 2 175 150 CaO CaO  MgO 125 100 WEIGHT OF 100% ALKALI 75 50 25 0 75 100 150 25 50 125 175 250 200 225 0 SULFURIC ACID 175 125 150 75 50 100 25 HYDROCHLORIC ACID 150 300 175 225 275 75 125 200 250 50 25 100 NITRIC ACID 25 50 75 100 HYDROFLUORIC ACID 75 25 125 100 50 HYDROCYANIC ACID WEIGHT OF 100% ACID * Reactions between acids and alkalies are exothermic and sometimes violent. Thus proper (normal and customary) safety precautions should be strictly followed. Waste Water TreatmentsIndustrial Waters • 1. pH adjustment • See alkali neutralization graph

  3. Waste Water TreatmentsIndustrial Water • 2. Coagulation/flocculation • coagulation: neutralization of the generally negatively charged particles • flocculation: formation of “flocs” • In conjunction with Al or Fe salts, lime is used for coagulating suspended solids by maintaining the proper pH for most satisfactory coagulation conditions • 3. Removal of phosphates, sulfates & fluorides • Precipitation of insoluble calcium salts that are readily recoverable • ex: 3 Ca(OH)2 + 2 H3PO4  Ca3(PO4)2 + 6 H2O

  4. pH 3 4 5 6 9 11 7 8 10 Waste Water TreatmentsIndustrial water 4. Precipitation of metals Adjusting pH level of waste water to form insoluble metallic hydroxides Me(OH)x Metal Aluminum Cadmium Chromium Cobalt Copper Iron Lead Manganese Mercury Nickel Silver Zinc Optimal pH zones for the precipitation of different metals

  5. LIME (Bulking) Sludge Return LIME LIME Primary Clarifiers Waste Water Activated Sludge Aeration Pretreatment Excess Solids Supernatent Secondary Clarifiers Treated Water LIME Sludge Recirculation Odor Treatment Sludge Digester Lime Treatment for Waste Water Treatment By Biological Aeration Digested Sludge Solids Waste Water TreatmentsMunicipal water • “Low lime” treatment before biological treatment - removal of phosphates • Odor control • Most of the lime used in sludge treatment

  6. Drinking Water Treatment • Drinking water strictly regulated • One important parameter of the quality of water is it’s hardness or it’s lime / carbon dioxide equilibrium: Ca(HCO3)2 CaCO3 + H20 + CO2 Too soft water  cardiovascular diseases Too hard water  scaling problems, increased use of soap...

  7. H2O Hard H2O milk of lime Drinking Water Treatments1. Softening • Purpose: remove the “carbonate” hardness from the water • 1. Prevent scaling in the pipes & installations • 2. Improve our living: less scaling in the bathroom, less use of soap & detergents… • Reaction: Ca(HCO3)2 + Ca(OH)2 CaCO3 precipitated + H20 • Example: Pellet reactor

  8. Drinking Water Treatments2. Remineralization3. pH adjustment / coagulation • Purpose: increase the hardness of a too soft (corrosive) water • - Protective coating on the inside of water mains • Reaction: H20 + Ca(OH)2 + 2 CO2 H20 + Ca(HCO3)2 • Purposes: - Adjust pH to prepare for further treatment - Coagulation of suspended solids with alum (Al) or iron (Fe) salts - Facilitating sludge thickening

  9. LIME LIME (Treatment of Oders) Digester Digester Primary Clarifiers FeCI FeCI Polymer OR OR OR Polymer 3 3 Filter Press LIME Pug Mill Centrifuge ChemicalConditioning ChemicalConditioning Centrifuge Filter Press Belt Press LIME QUICKLIME Vacuum Filter Solids SludgeSemi-Solids SludgeSemi-Solids Pug Mill Lime uses for dewatering sludge solids Solids StabilizedSludge Solids Lime uses for Dewatering Sludge Solids Sludge Treatments Lime treatment • Converts sludge in a usable product • Really cost-effective option when the treated sludge is used on the lands

  10. Sludge Treatments • BEFORE MECHANICAL Dewateringuse of lime: - Facilitates the dehydration process - Destroys pathogens (pH > 12) - Destroys and prevents formation of odors - Precipitation of most metals & reduction of their solubility and mobility • AFTER MECHANICAL Dewateringuse of quicklime CaO: - Exothermic reaction : pasteurization of the sludge - Higher solid content of waste: easier handling and storage - Destruction of pathogens and limitation of the odors • - Non negligible calcium supply

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