10.4 Ex-situ- Liquid Phase

1. 10.4 Ex-situ- Liquid Phase Materials are taken from the Textbook: Hazardous Waste Management. 2nd Ed. Legrega et al., McGraw Hill

2. Useful links http://www.pubs.asce.org/WWWsrchkwx.cgi?Biofilm http://www.pubs.asce.org/WWWsrchkwx.cgi?Filters http://www.pubs.asce.org/WWWdisplay.cgi?5016176 http://www.pubs.asce.org/WWWsrchkwx.cgi?Design+improvements http://www.frtr.gov/matrix2/top_page.html http://www.frtr.gov/matrix2/section3/table3_7_fr.html

4. Mixing regime • Hydraulic retention time (HRT) • Solid retention time (SRT) • Total dissolved solids • Other factors • Equalization • Chemical treatment • Physical separation • Conditioning

5. Ex-situ-Liquid Phase • Aerobic batch • Anaerobic batch • Continuous flow and aerobic suspended growth • PAC • Attached growth • Submerged fixed-film • Fluidized-bed

7. Fig. 10-13 Fig. 10-13 10.4

9. SBR

10. Anaerobic batch system

14. MBR • Crossflow UF: MLSS 30,000 mg/L • MF: MLSS 15,000 mg/L http://www.ionics.com/technologies/mbr/index.htm#

15. RBC • Bioreactors degrade contaminants in water with microorganisms through attached or suspended biological systems. • In suspended growth systems, such as activated sludge, fluidized beds, or sequencing batch reactors, contaminated ground water is circulated in an aeration basin where a microbial population aerobically degrades organic matter and produces CO2, H2O, and new cells. • The cells form a sludge, which is settled out in a clarifier, and is either recycled to the aeration basin or disposed. • In attached growth systems, such as upflow fixed film bioreactors, rotating biological contactors (RBCs), and trickling filters, microorganisms are established on an inert support matrix to aerobically degrade water contaminants.

16. 10-5 Ex-situ-Slurry Phase

18. Slurry Phase Systems • In-situ • Ex-situ • Pretreatment • Desorption • Concentration of solids • Mixing

19. Pretreatment • Enhanced desorption • Surfactants and size reduction • Waste consent ration • Size fractionation

20. Desorption • Rate of degradation is a function of the concentration in solution rather than on the surface • Microbial populations grow linearly rather than logarithmically

21. Concentration of solids in reactor • As low as 5% as high as 50% (dry weight) • Typical 30-40%

22. Mixing (Agitation) • Breakdown of solid particles • Desorption of waste from solid particles • Contact between organic waste and microorganisms • Oxygenation of the slurry be aeration • Volatilization of contaminants

23. Mixer design • Dual drive • Axial flow impellers: 20 – 30 rpm • Rake arms: 2 rpm

24. Applications • Wood-preserving wastes • Contaminated soils

25. 6

32. Enhanced Bioremediation • Typical Oxygen-Enhanced Bioremediation System for Contaminated Ground water with Air Sparging • Oxygen-Enhanced H2O2 Bioremediation System • Typical Nitrate-Enhanced Bioremediation System  

33. Enhanced Bioremediation

34. Oxygen Enhancement with Air Sparging • Air sparging below the water table increases ground water oxygen concentration and enhances the rate of biological degradation of organic contaminants by naturally occurring microbes. • Air sparging also increases mixing in the saturated zone, which increases the contact between ground water and soil. • The ease and low cost of installing small-diameter air injection points allows considerable flexibility in the design and construction of a remediation system. • Oxygen enhancement with air sparging is typically used in conjunction with SVE or bioventing to enhance removal of the volatile component under consideration.

35. Oxygen Enhancement with Hydrogen Peroxide • During hydrogen peroxide enhancement, a dilute solution of hydrogen peroxide is circulated through the contaminated ground water zone to increase the oxygen content of ground water and enhance the rate of aerobic biodegradation of organic contaminants by naturally occurring microbes.

36. Nitrate Enhancement • Solubilized nitrate is circulated throughout ground water contamination zones to provide an alternative electron acceptor for biological activity and enhance the rate of degradation of organic contaminants. • Development of nitrate enhancement is still at the pilot scale. • This technology enhances the anaerobic biodegradation through the addition of nitrate. • Fuel has been shown to degrade rapidly under aerobic conditions, but success often is limited by the inability to provide sufficient oxygen to the contaminated zones as a result of the low water solubility of oxygen and because oxygen is rapidly consumed by aerobic microbes. • Nitrate also can serve as an electron acceptor and is more soluble in water than oxygen. • The addition of nitrate to an aquifer results in the anaerobic biodegradation of toluene, ethylbenzene, and xylenes. • The benzene component of fuel has been found to biodegrade slower under strictly anaerobic conditions. • A mixed oxygen/nitrate system would prove advantageous in that the addition of nitrate would supplement the demand for oxygen rather than replace it, allowing for benzene to be biodegraded under microaerophilic conditions.