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Water / Wastewater Treatment

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  1. American Bar Association Forum on the Construction Industry Water / Wastewater Treatment Presented By: Brad Wolf, PE Berkeley Research Group Danielle J. ColePeckar & Abramson

  2. Part 1: Water Treatment

  3. Greeley, Colorado

  4. Treatment is Essential • Manufacturing • Power Generation • Chemical Production • Pharmaceutical • Health Care • ¾ of earth surface is covered in water, but only one-half of one % is fresh and even a smaller portion of that is usable

  5. Treatment Methods • Chemical Process • Environmental Process • Mechanical Process • Plant Design features (Civil Engineering) • Filtration Systems • Skimmers • Ultraviolet Light • Ozone • Permeable Membranes

  6. Water is a Universal Solvent • Carry Nutrients and Chemicals • Support Chemical Reactions • Suspend Materials • Supports Life • Carry Disease

  7. Purification for Drinking Water Must Be Measured • Measurements must be taken at the plant and during transmission (grab samples) • Identify Bacteria, Viruses, Organics and other constituents.

  8. Environmental Protection Agency (EPA) • Leading Federal Agency Establishing and Enforcing Water Quality Standards • Clean Water Act • Standards for Discharge • Safe Drinking Water Act & Amendments • Standards for impurities in drinking water

  9. Water Treatment Plants • Design Considerations: • What quality and quantity of water is required? • What raw water supply is available? • What type of plant process is necessary? • Engineering determined by • Water available • EPA standards for the water • Quantity of water needed • Treatment technologies

  10. EVALUATINGRAW WATER SUPPLY • Variation in Availability • Does raw water quality vary a lot by season • Control Supply of Water and Quality • Inability to Control Water and Quality • Large or small body of water as supply • River water supply and consistency of flow • Groundwater • Seawater

  11. TESTING • Microbial Testing • Testing performed on sample and if microorganisms are present assume others of the same are present and they spring from the same source • Evaluating Water Chemistry • Easier: Possible indicator of microbial presence

  12. Treatment Plant Size (MGD) • Cost Considerations • Size of Population to be served (75 to 150 gallons per day per person) • Contact Time • How Long does disinfectant need to be in the water to be effective

  13. CIVIL & STRUCTURAL DESIGN Physical Structure Design Transportation of Water Tanks and Pumping

  14. SUSTAINABLE DESIGN • Minimize Waste From Plant • Minimize Power Use • Triple Bottom Line • People • Planet • Profit

  15. Plant Instrumentation and Construction • Instrumentation necessary to monitor raw water coming in and effluent going out and distribution system • Construction decision between private and public management • Cost Considerations • Long Term Maintenance Considerations

  16. Plant Instrumentation and Construction (Scada)

  17. Plant Instrumentation and Construction (Scada)

  18. Plant Instrumentation and Construction (Scada)

  19. Source of Water to Plant • GROUNDWATER • Springs and Wells • Higher in dissolved solids and hardness • Pumped & Artesian Wells • OCEAN • High Cost to Remove Salt – but margin is narrowing • SURFACE WATER • Affected by the environment

  20. Desalination Plants

  21. Water Purification Processes • Primary Components • Gathering Raw Water • Series of Purification Steps • Storage, pending distribution

  22. Denver, Colorado

  23. Effluent Structures • Choice of Structure Depending on Source • Water Availability • Bathymetry • Sediment Transport • Environmental Regulations • Climatic Conditions • Constructability • Operations and Maintenance

  24. Pumping Considerations

  25. Pumping Considerations • Pump choice determined by pressure needed in processing water. • Pump considerations moving water to higher elevations • Pump considerations dependant on size of pipe and allowable pressure • Energy Use – efficiencies derived from variable speed drives

  26. Treatment Process

  27. City of Denver 5 Step Treatment Process 1. Coagulation/flocculation- Raw water from reservoirs is drawn into mixing basins at our treatment plants where we add alum, polymer and sometimes lime and carbon dioxide. This process causes small particles to stick to one another, forming larger particles. 2. Sedimentation- Over time, the now-larger particles become heavy enough to settle to the bottom of a basin from which sediment is removed. 3. Filtration- The water is then filtered through layers of fine, granulated materials (sand, sand/coal, etc.). As smaller, suspended particles are removed, turbidity diminishes and clear water emerges. 4. Disinfection- To protect against any bacteria, viruses and other microbes that might remain, disinfectant is added before the water flows into underground reservoirs throughout the distribution system and into your home or business. (example – chlorine). 5. Corrosion control- pH is maintained by adding alkaline substances to reduce corrosion in the distribution system and the plumbing in your home or business.

  28. Treatment Process • Chemical Injection • Carefully monitored uring the treatment process to maintain maximum efficiency • Chlorine • Effective disinfectant best used on warmer water • Ammonia • Used to limit disinfection by-product caused by chlorine • Potassium Permanganate • Controls color, taste and odors • Acids and Caustics • Used to control pH level of water

  29. Treatment Process • Flocculation • Add chemicals to water to cause suspended solids to coagulate and become larger to be removed by filters • Sedimentation • Low flow velocity basins allowing solids to drop out • Ozone Disinfection • Control of carbon based materials in water • Ultraviolet Germicidal Irradiation • Use of light to destroy microbes in water

  30. Filtration • Rapid Sand Filters • Passing water through sand beds to remove solids • Slow Sand Filters • Graded layers of sand filters water as it passes • Activated Carbon Adsorption • Uses adsorption to capture organics • Membrane Filtration • Operate at the molecular level

  31. Membrane Type of Filters • Ultrafiltration • Separate large organic molecules and colloidal silica • Nanofilters • Capable of removing hardness, heavy medals, color, taste and large organics • Reverse Osmosis • Predominately used for desalinazation

  32. Membrane Type of Filters Ultrafiltration Nanofiltration Aeration Reverse Osmosis (desal)

  33. Final Treatment

  34. Final Treatment • Chemical treatment of water to disinfect • Final treatment of waster as regulated by the Environmental Protection Agency and state Departments of Health

  35. Part 2: Wastewater Treatment

  36. How it works • A combination of civil engineering, biology and chemistry • Weirs, Clarifiers • Aerobic, Anaerobic • Dissolved Oxygen, Eutrophication

  37. Wastewater Treatment and Distribution

  38. Brighton, COProject Completion: 2015

  39. Regulatory Scheme • Prior to 1947 – no regulation of waste water • 1948 to 1970 – Federal Water Pollution Control Act (FWPCA) • 1970 to Present – EPA Clean Water Act • Controls the discharge of all pollutants into above ground waters • Ensure that surface waters would meet standards necessary for human sports and recreation

  40. Preliminary Wastewater Treatment • Screening • Coarse Screens and Bar Screens • Removes Large Items • Fine Screens – Static, Rotary Drum or Step • Removal of Fines • Grit Removal • Removal of coarse suspended material (silt, sand and gravel) • Gravity / Velocity grit removal • Aerated Grit Chamber • Shredding or Grinding • Shred or grind material in the flow to reduce the size of the inert material so it does not interrupt the process

  41. Preliminary Treatment • Flow Equalization • Plant is most efficient if constant flow is maintained • Peak flows mid-morning and evening • Construct equalization basin to release constant flow to plant • Must aerate and mix liquids in basin to prevent oder and settling solids.

  42. EquilizationBasin – Pendleton, SC

  43. Primary Treatment • Remove settled organics and floatable solids • Primary Clarifiers • Flow Velocity Decrease • Solids settled out – sludge pumped off http://techalive.mtu.edu/meec/module21/WastewaterPrimaryTreatment.html Michigan Environmental Education Curriculum

  44. Enhancing Primary Treatment • Pre-aeration • Introduction of air in the grit chamber • Promotes flocculation, scum floatation and removal • Benefits odor control • Coagulation • Chemical introduction to promote the settling of finely dispersed solids to promote forming large solids out of finely dispersed solids

  45. Coagulation Process

  46. Secondary Treatment • Process to convert organic wastes to move more stable solids that can either be removed by settling or discharged to the environment, without causing harm. • Biological process involve the use of microorganisms in the treatment system

  47. Secondary Treatment Cont. • Fixed Film System • http://www.youtube.com/watch?v=Hdn6zqSHK6Y • Trickling Filters – waste water distributed over a media, air added to media and bio-film grows and sloughs off • Rotating Biological Contractor • Rotating disks equally apply oxygen to microorganisms attached to disks. The build up is removed • Suspended Growth System • Treatment Ponds • Secondary Sedimentation