Overview of Water Quality

1. Overview of Water Quality University Curriculum Development for Decentralized Wastewater Treatment Fundamental Concepts for Environmental Processes Kenimer et al., 14 September 2004 FINAL

2. Water Resources • Amount of water on Earth • 1.36x1018 m3 • 3.6 x 1020 gal • Fresh water • 2.8% (1.01 x 1019 gal) • 22% (2.22 x 1018 gal) is liquid • 0.6% (1.33 x 1016 gal) is accessible • 0.004% of Earth’s water is available for use

3. Water Resources • Why worry about shortages? • Water quality • Location • Timing (seasonal) • Use conflict • Drawdown and salt water intrusion

4. Types of water usage • Consumptive • water is unavailable for further use • Nonconsumptive • water is available for further use with treatment • Nonwithdrawal • water uses that do not require removal from it’s natural location

5. Fresh Water Usage

6. Water Resources Planning • Objective - meet expected requirements of diverse uses as defined by • economics • ecology • society • physics

7. Water Resources Planning • Estimate current and future needs • Appraise solutions to meet defined needs • Select optimum solution to the anticipated needs

8. Water Resources Planning • Water demand • Water supply • Water quality • Water storage • Wastewater discharges • Ecological impacts • Benefits gained • Technology required

9. Emerging Water Supply Technologies • Large-scale diversions • Desalination • Water reuse

10. Water Regulations • The Water Pollution Control Act Amendments of 1972 (PL 92-500) - Clean Water Act • Safe Drinking Water Act of 1974 • The Water Quality Act of 1987 (PL 100-24) • 1985 Food Security Act (PL 99-198)

11. Water Pollution • Definition: any condition that adversely affects the quality of streams, lakes, oceans, or groundwater

12. Sources of Pollutants • Point sources • enter receiving waters at identifiable locations • wastewater treatment plant effluent • runoff from large cities • runoff and leachate from mining operations • runoff from confined animal feeding operations (CAFOs) • runoff from large construction sites • discharges from shipping vessels

13. Sources of Pollutants • Non-point sources • everything that isn’t a point source • runoff from agricultural lands • irrigation return water • runoff from unsewered areas • small construction sites

14. Water Pollution Impacts • Unpolluted water has a wide diversity of aquatic organisms and contains enough dissolved oxygen to support them • Polluted water inhibits the growth of aquatic organisms

15. Reference Material • Standard Methods for the Analysis of Water and Wastewater. American Water Works Association and the American Public Health Association. • EPA Methods and Guidance for the Analysis of Water. US Environmental Protection Agency.

16. Solids Cause many problems: • Collect in treatment and distribution systems • May clog distribution areas in poorly-managed systems • Fill storage areas, clog ditches and channels • Settle on stream bottoms resulting in death of valuable benthic biota and loss of habitat and dissolved oxygen in the water column

17. Total Solid (TS) • Total solids of a sample is the matter left behind after drying a sample of water at 105 °C • Sample is left in oven until no further weight loss occurs (normally 24 h)

18. Total Solids Solid materials may be classified as • Suspended solids or dissolved solids • Volatile solids or fixed solids

19. Solids • Total suspended solids are the solids in the sample that may be caught with a 1.5 µm filter • Total dissolved solids are the solids in the sample that will pass through the filter

20. Solids • Total volatile solids is the portion of the dried solids lost after they have been heated to 550 °C. It is an approximation of the organic material present. • Total fixed solids is the portion that still remains after heating the dried solids to 550 °C. It is an approximation of the mineral matter present (ash content).

21. Solids • These categories may be combined: • Volatile dissolved solids (VDS) • Volatile suspended solids (VSS) • Fixed dissolved solids (FDS) • Fixed suspended solids (FSS)

22. Solids Total Solids Suspended Dissolved Volatile Fixed Volatile Fixed

23. Solids Content • The mass of solids per known volume of water is: • S = Solids concentration (mg/L) • mt = Mass of solids and container (mg) • mc = Mass of container (mg) • Vol = volume of liquid sample (L)

24. Solids Content • Sometimes solids content is given as a percentage • for a dilute solution or suspension, this is the mass of solids in g per 100 mL of solution or suspension (100 mL has a mass of 100 g):

25. Turbidity • Turbidity is a measure of the clarity of water. • Turbidity is influenced by the number of insoluble particles present

26. Nutrients Problems associated with excess nutrients: • Cause an increase in productivity of aquatic plants, leading to depleted DO levels • May cause odor problems • Extra vegetation near surface may inhibit penetration of light into water

27. Nutrients • Macronutrients: • Nitrogen • Nitrate (NO3) • Nitrite (NO2) • Ammonia (NH3) • Organic N • Total Kjeldahl Nitrogen (TKN) • Phosphorus • Orthophosphates (ortho-P) • Polyphosphates • Organic phosphorus • Potassium

28. Microbial Organisms • Serve many important purposes including degrading waste materials • Some of them may be dangerous to human health and must be removed from water

29. Testing for Microbial Organisms • Fecal coliform counts are used as an indicator organism • The sample material is placed on a nutrient agar and set aside in a sterile area • The number of colonies that form is proportional to the number of microorganisms present in a sample

30. Salts Problems associated with excess salt: • High salt concentrations are detrimental to plant growth and can damage crops. • Salt can damage equipment, especially some materials which react with the salts.

31. Metals Problems associated with excess metals: • Can make water taste and smell bad • Can stain • Metals in high enough concentrations are pollutants and can be serious health risks.

32. Hardness • Hardness is the concentration of multivalent cations such as calcium. • Hard water can leave scale in pots, pipes, and hot water heaters. More soap is also needed to clean. • Soft water has predominantly monovalent cations such as sodium, making it harder to remove soap residue.

33. pH • pH is the negative log of the hydrogen ion concentration: pH = − log [H+] • pH can have a major impact on biological and chemical reactions

34. Alkalinity • Alkalinity is the capacity of water to absorb hydrogen ions without significant pH change • Bicarbonates, carbonates, and hydroxides are the three chemical forms that contribute to alkalinity

35. Dissolved Oxygen • Dissolved oxygen is oxygen that has been incorporated into water as a solute (not a separate phase like bubbles) • Many aquatic animals require it for their survival

36. Dissolved Oxygen • There are two important factors that can influence the amount of dissolved oxygen present • Water temperature • Organic matter

37. Saturation Concentration of O2 in Water

38. Dissolved Oxygen • Organic material • If oxygen is available, organic material requires oxygen to decompose • Organic material may also decompose in the absence of oxygen • More organic material requires more DO, and will tend to deplete water of DO

39. Oxygen Demand • The oxygen demand is the amount of oxygen required to aerobically oxidize a material

40. Biochemical Oxygen Demand • Biochemical oxygen demand, or BOD, is the amount of oxygen used by organisms during the breakdown of organic material • BOD is considered an indirect measure of the organic content of a sample

41. BOD • BOD analysis is done under these conditions: • Must be in the dark • Must be at 20ºC • Must have an excess of inorganic nutrients

42. BOD5 Procedure • Measure initial DO • Incubate sample for 5 days • Measure final DO • The BOD5 is directly related to the amount of DO consumed over the 5-day period

43. BOD • BODt= BOD at t days (mg/L) • DOi = Initial DO (mg/L) • DOf= Final DO (mg/L) • Vs = Volume of sample (L) • Vb= Volume of liquid in BOD bottle (L)

44. Ultimate BOD • The ultimate BOD is the total amount of organic compounds biologically degraded plus oxidation of nitrogen compounds that nitrify over time BOD carbonaceous + BOD nitrogenous = ultimate BOD

45. Kinetics of BOD Breakdown • BOD breakdown is a first order reaction in terms of BOD remaining • The BOD consumed over time is

46. Typical values for k at 20°C

47. DO of Flowing Water • Flowing water has some capacity for self-purification as long as discharge of organic matter (BOD) into the stream is not too great. To maintain this capacity, a balance is needed between • DO consumption to break down BOD • oxygen transfer to reaerate the stream

48. Chemical Oxygen Demand (COD) • COD is the equivalent amount of oxygen needed to break down organic matter and reduce nitrogen compounds using a strong oxidizing agent

49. Chemical Oxygen Demand • Approximation of BOD • Faster than BOD • Always higher than BOD • COD is much higher than BOD in raw wastewaters • COD:BOD ratio is usually less than 2:1 in treated effluents • COD:BOD ratio is dependent on circumstances and decreases with treatment

50. Total Organic Carbon • Total organic carbon, or TOC, is the amount of organic carbon bound in a sample.