Management of Non-Point Source Pollution CE 296B

1. Management of Non-Point Source PollutionCE 296B Department of Civil Engineering California State University, Sacramento Lecture #9, March 3, 1998 Sources of Pollutants - Part V

2. Recall that we were looking at the six categories of pollutants: 1. Toxic inorganics - e.g. metals 2. Synthetic organics - e.g. solvents 3. Biostimulants - BOD, nutrients 4. Sediment - clay, silt, sand, gravel  Left off here 5. Pathogenic organisms - viruses, bacteria, protozoa 6. Trash - use your imagination

3. And the framework for acquiring knowledge about each category: • 1. What are the sub-categories in each category and what are representative members? • 2. What are the origins of pollutants? • 3. How pollutants are introduced to the flow stream? • 4. How pollutants behave in water? and here

4. V. The fourth category of pollutant to examine is sediment. (cont.) D. How do sediments behave in water? Divided into three major groups, each one having it’s own effect on water quality objectives and beneficial uses: • Transport of particles - Sedimentation effects (mass loading). • Adsorption of other materials - Major determining factor for where toxic substances end up and effect they have. • Contribution to turbidity - Concentration effects.

5. V. The fourth category of pollutant to examine is sediment. (cont.) • D. How do sediments behave in water? (cont.) 1. Transport of particles: a. Two modes of transport- • Suspended in the flow - Wetload • Being pushed along the bottom - Bedload b. Particle size distribution, wetload vs. bedload: Obviously, wetload transport has a smaller particle size distribution than bedload.

6. Wetload Particle Transport I. Questions associated with wetload particle transport can be separated into two categories: A. What is the largest, discrete, particle that will remain in suspension? Particles that are less than 1 µm in diameter are colloidal and will remain in suspension as surface forces are greater than body forces. It is the size of the particle greater than 1 µm in diameter that will remain in suspension. B. How much aggregation of particles is taking place? The idea being that larger, aggregated particles are more likely to become part of the bedload.

7. Where:  = Flow velocity D = Stream width µ = Fluid Viscosity Wetload Particle Transport II. What controls the size of the largest, discrete particle that will remain in suspension? • For particles greater than 1 µm in diameter, body forces are dominant. Unless held in suspension physically by turbulence, the particle will settle. Thus, as turbulence is proportional to the Reynolds Number, the greater Reynolds Number associated with the flow, the larger the particle that will remain in suspension.

8. Wetload Particle Transport II. How much aggregation of particles is taking place? Complex topic, but lessons learned from the coagulation process apply here as well. Aggregation is dependant on (among other things): • The concentration of multivalent cations (Ca+2, Mg+2) present. Higher concentrations mean greater aggregation. • The concentration of univalent cations (Na+, K+) present. Higher concentrations mean less aggregation.

9. Wetload Particle Transport II. How much aggregation of particles is taking place? Complex topic, but lessons learned from the coagulation process apply here as well. Aggregation is dependant on (among other things): (cont.) • An appropriate velocity gradient (G). • Too large a gradient, and shear forces will tear aggregated particles apart. • Too small a gradient, particles will have inadequate opportunity to come into contact.

10. Wetload Particle Transport III. Thus, the amount of wetload, particulates that will be transported rapidly, is dependant on: A. The amount and composition of material originally eroded. B. The turbulence of the flow stream, either in a natural or man-made channel. C. The composition of electrolytes in the flow stream. IV. It is important to note that while fine particles are suspended in the wet load, partitioning of metals and synthetic organics to the solid phase is enhanced.

11. Bedload Particle Transport I. Particles too heavy to remain in suspension may still be transported along the bottom of a channel, natural or man-made, by the force of the current and the assistance of gravity. Of interest in the examination of bedload transports is: • The mass flow rate of sediment in the downstream direction. • The fractionation of sediments by size as part of the bedload transport process. • The disposition of sediments when transport ceases.

12. Bedload Particle Transport II. The mass flow rate of sediment in the downstream direction is complex (translation, I don’t know much about it yet). Factors include: • The amount and type of erosion in the watershed. • The bottom composition (roughness) - a smoother surface yields a greater transport rate. • The flow velocity - higher velocity yields a greater transport rate. • The slope - a steeper slope yields a greater transport rate.

13. Discussion Break Based on what you have seen, and knowledge of gravity flow system design, how efficiently will sediments, of all sizes, be transported once they enter the system? Focus of BMP’s?

14. At periodic states of equilibrium, the potential energy of each particle is nearly equal. m1gh1 = m2gh2 = m3gh3 Streambed at quasi-equilibrium Particle 1, m1 Particle 2, m2 Particle 3, m3 So h1 h2 h3 Bedload Particle Transport III. The fractionation of sediments by size. Consider the diagram: Thus, along the streambed, natural or man-made, there will be a sorting out of particles by size to satisfy first law concerns. So, gravel deposits, sandbars, mudflats!

15. Discussion Break All other things being equal, where would you expect to find the greatest concentration of toxic substances? Basis: Mass of contaminant per mass of dry soil (mg/kg) Gravel Beds? Sandbars? Mudflats?

16. Bedload Particle Transport III. The disposition of sediments when transport ceases. Two different types of issues are addressed: A. Are the effects of sediment deposits positive or negative? • Positive: • Spawning grounds and beaches (gravel / sand) • Entombment of toxic substances • Negative: • Filling of wetland habitat type effects • Impairment of navigation

17. Bedload Particle Transport III. The disposition of sediments when transport ceases. Two different types of issues are addressed: (cont.) B. Are the deposits permanent or temporary? If they are permanent, the same issues discussed previously will be valid. If temporary: • Will a large flow event, clearing out the deposit cause a “shock loading” problem downstream? • Will the inevitable large flow event “clean out” a: • positive deposit (beach, spawning ground)? • negative deposit (clogged wetland)

18. V. The fourth category of pollutant to examine is sediment. (cont.) • D. How do sediments behave in water? (cont.) 2. Adsorption of toxic substances to particles. Two different aspects to this topic: • How much and how tightly are toxic substances bound to particulate material? • Is this removing toxic substances from liquid phase and thus making them less bioavailable or is this concentrating toxic substances in one place (the bottom sediments)?

19. V. The fourth category of pollutant to examine is sediment. (cont.) • D. How do sediments behave in water? (cont.) 3. How much and how tightly are toxic substances bound to particulate material? In other classes, substaintial effort has/is/will be made on behalf of partitioning of metals, synthetic organics to the soil matrix (or activated carbon). The equilibrium relationships developed there only applies to the circumstance pore water within a matrix.

20. V. The fourth category of pollutant to examine is sediment. (cont.) • D. How do sediments behave in water? (cont.) • 3. How much and how tightly are toxic substances bound to particulate material? (cont.) Many of the same principles apply to adsorption of metals and synthetic organics to soil particles suspended in a water matrix, but the equilibrium equations do not.

21. V. The fourth category of pollutant to examine is sediment. (cont.) • D. How do sediments behave in water? (cont.) • 3. How much and how tightly are toxic substances bound to particulate material? (cont.) New, yet to be developed relationships may describe the equilibrium between liquid phase concentrations and adsorbed phase amounts for metals and synthetic organics with respect to soil particles suspended in a water column.

22. V. The fourth category of pollutant to examine is sediment. (cont.) • D. How do sediments behave in water? (cont.) • 3. How much and how tightly are toxic substances bound to particulate material? (cont.) Factors that would be considered in such a relationship: • Concentration of solids • Clay fraction • Organic fraction • Temperature • Hardness • Mixing • Contact time • pH

23. V. The fourth category of pollutant to examine is sediment. (cont.) • D. How do sediments behave in water? (cont.) 4. Finally, wetload sediment transport contributes to increased turbidity. In addition to being a water quality objective, turbidity can: • Have a negative effect on fish. Particulate material and gills do not mix. • Although the correlation is very poor, turbidity measurements can be a surrogate measure for sediment concentration.

24. Recall that we were looking at the six categories of pollutants: 1. Toxic inorganics - e.g. metals 2. Synthetic organics - e.g. solvents 3. Biostimulants - BOD, nutrients 4. Sediment - clay, silt, sand, gravel On to here  5. Pathogenic organisms - viruses, bacteria, protozoa 6. Trash - use your imagination

25. And the framework for acquiring knowledge about each category: • 1. What are the sub-categories in each category and what are representative members? • 2. What are the origins of pollutants? • 3. How pollutants are introduced to the flow stream? • 4. How pollutants behave in water?

26. VI. The fifth category of pollutant to examine is pathogens. A. Define what pathogens are: A pathogen is a microscopic entity that if a sufficient dose is transmitted to a human, a disease will ensue. Three broad categories of pathogens exist: 1. Viruses 2. Procaryotes 3. Eucaryotes

27. Viruses • Viruses (from the Latin virus - poisonous substance) are infectious nucleic acid encapsulated in a protein coat. • A virus reproduces by invading a cell, where replication takes place. The cell then dies releasing many copies of the virus. • A philosophical debate exists as to whether a virus is alive. After all as an entity, it has no metabolic functions. All it does is invade another cell and let the that cells metabolic machinery do all the work for reproduction.

28. Viruses • In most cases a virus has a specific type of cell it is capable of invading. • Viruses are small. The size range is 20 - 350 m. 50 m is typical. • Traditional methods of detecting viruses involve tissue cultures, looking to see in the correct type of cells grown in culture are infected. • This makes detection in water samples extremely difficult. • Example water borne pathogen - Polio

29. Discussion Break Why do you think it is so difficult to detect viruses in water samples? Policy implications?

30. Cell Membrane Cytoplasm DNA 2 µm 0.8 µm Procaryotes • Procaryotes, loosely bacteria, are single celled organisms capable of metabolic functions that do not have a nucleus. • Structure • Typical Size

31. Procaryotes • By far, the largest source of biomass on the planet. • As bacterial species are difficult to differentiate by morphology, bacteria are usually classified by the biochemical processes they do best. • Most schemes to detect bacteria are centered on isolating species based on biochemical tests. Does the bacteria perform a particular biochemical process. • A major problem with this approach has been that many species will perform a given biochemical process.

32. Procaryotes • Pathogenic bacteria can be vectored many ways, but we are interested in water borne pathogens. The most likely source of bacterial pathogens in water is fecal matter. • Examples of water borne pathogens: • Cholera: Vibrio cholerae • Typhus: Salmonella typhi The pathway for infection is the same for both species. After an infected host contaminates a water supply, the richest source being fecal matter, a victim ingests water that contains a large enough number of viable organisms to become infected.

33. Eucaryotes • Eucaryotes, loosely protozoa, are organism where the cell(s) have a nucleus. • Size: Huge variation, but much larger than bacteria. • Reproduce much slower than bacteria, and thus occur in much lower numbers. • Many fewer viable organisms are required to cause an infection. • Are far tougher than bacteria or viruses. Can withstand environmental stress better and are more resistant to disinfection.

34. Eucaryotes • Often are parasitic. Treatment is notoriously difficult. • Because of: • Low population densities, and • Poorly understood biochemistry are very difficult to detect. • Example pathogens: • Giardia lambilia • Crytposporidium • Entamoeba histolytica

35. Eucaryotes • The life cycle of these organisms are usually poorly understood. It is often assumed, without proof, that the major source of contamination is fecal matter. • Other than minimizing fecal matter, a difficult chore for wild animals in any case, source control measures are hard to come by for eucaryotic organisms.

36. Discussion Break Diarrhea kills more people worldwide than any other cause. In the U.S., it is not a big problem. How real do you think the problem of water borne disease is in this country?

37. VI. The fifth category of pollutant to examine is pathogens. (cont.) B. Overview of detection of pathogens in surface waters: 1. The number of possible pathogens is huge. Each pathogen has a specific test associated with it. Many of those tests are difficult and expensive to perform. 2. A solution to this problem was put forward at the turn of the century. That solution is still the regulatory standard.

38. VI. The fifth category of pollutant to examine is pathogens. (cont.) • B. Overview of detection of pathogens in surface waters: (cont.) 3. The idea was to test for an organism that was found in fecal material, but that had no other source. 4. Scientists searched for a biochemical process that only took place in the intestinal tract of warm-blooded animals. The choice was the fermentation of lactose in the presence of bile salts.