Disposal and Treatment of Biosolids

1. Disposal and Treatment of Biosolids John Scott Meschke Office: Suite 249N, 4225 Roosevelt Phone: 206-221-5470 Email: jmeschke@u.washington.edu

2. What are Biosolids? Sewage? Sludge?

3. Biosolids are: • “wastewater solids that meet quality standards for land application” • Sewage Sludge-”a solid, semi-solid or liquid residue generated during the treatment of domestic sewage ina treatment works” • Septage – “liquid or solid material removed from a septic tank, cesspool, …or similar system that receives only domestic sewage”

4. How are biosolids generated and processed?

5. Conventional Community (Centralized) Sewage Treatment Pathogen Reductions Vary from: low (<90%) to Very High (>99.99+%)

6. Typical Municipal Wastewater Treatment System

7. Waste Solids (Sludge) Treatment • Treatment of settled solids from 1o and 2o sewage treatment • Biological “digestion” to biologically stabilize the sludge solids • Anaerobic digestion (anaerobic biodegradation) • Aerobic digestion (aerobic biodegradation) • Mesophilic digestion: ambient temp. to ~40oC; 3-6 weeks • Thermophilic digestion: 40-60oC; 2-3 weeks • Produce digested (biologically stabilized) sludge solids for further treatment and/or disposal (often by land application) • “Thickening” or “dewatering” • drying or “curing”

8. Waste Solids (Sludge) Treatment • Waste liquids from sludge treatment are recycled through the sewage treatment plant • Waste gases from sludge treatment are released (or burned if from anaerobic digestion: methane, hydrogen, etc.)

9. Biosolids Treatment • At the Wastewater plant: • High temperatures • Chemical disinfectants • Destruction of food source • Desiccation • Predation and competition

10. Biosolids Treatment • Land application: • Heat • Sunlight • Further dessication • Unfavorable pH • Indigenous microflora

11. What steps beyond treatment may be used to reduce public exposure?

12. Site management (restricted access) • Class A biosolids • No restriction on time of use • Class B biosolids • 30 days for livestock grazing • Up to 38 months for harvest of root crops • What based on?

13. Biosolids Quality • Pathogens content • Trace elements content • Vector attraction

14. What are EQ biosolids?

15. EQ Biosolid Requirements • Trace element content below required levels • Class A standards • One of 8 vector reduction alternatives • Monitoring • Certification Statement • Annual Reports

16. What are the rules and regulations that govern the processing and application of biosolids?

17. Regulations • 40 CFR part 503 (Federal Regs) • RCW Chapter 70.95J (directs beneficial use) • RCW Chapter 70.96J.005 (creates recycling program) • WAC 173-308 (defines beneficial use; biosolids management plan)

18. How are Biosolids used or disposed of?

19. Where are they used?

20. What are the potential public health concerns associated with the use of biosolids?

21. Infectious Disease • For disease, must be: • Host • Pathway • Infectious Dose Treatments designed to interrupt one or more of these elements to prevent disease

22. Enteric Microbe/Pathogen Reductions by Sludge Treatment Processes • Anaerobic and aerobic digestion processes • Moderate reductions (90-99%) by mesophilic processes • High reductions (>99%) by thermophilic processes • Thermal processes • Reductions depend on temperature • Greater reductions at higher temperatures • Temperatures >55oC usually produce appreciable pathogen reductions. • Alkaline processes: lime or other alkaline material • Reductions depend on pH; greater reductions at higher pHs • pH >11 produces extensive pathogen reductions • Composting: high temperature, aerobic biological process • Reductions extensive (>99.99%) when temperatures high and waste uniformly exposed to high temperature • Drying and curing • Variable and often only moderate pathogen reductions

23. Class A Biosolids Class A Biosolids: • <3 Salmonella per 4 grams of dried sludge solids • <1,000 fecal coliforms per gram dry sludge solids • <1 virus per 4 grams dried sludge solids • <1 viable helminth ovum per 4 grams dried sludge solids

24. Class A Treatment Alternatives • Thermally treated biosolids (time and temp requirments) • High pH and High temp (pH >12 for 72 hours, temp >52C, air dired to 50%) • Other processes that can be demonstrated to remove helminth ova and viruses • Unknown processes that can be demonstrated to remove helminth ova and viruses • PFRPs • Equivalent PFRPS

25. PFRPs • Composting • Vessel (≥55°C, 3 days) • Windrow (≥55°C, 15 days) • Heat drying (80°C, 10%moisture) • Heat treatment (180°C for 30 min) • Thermophilic aerobic digestion (55-60°C, 10 days) • Beta ray irradiation (1megarad) • Gamma ray irradiation (Cobalt 60 Cesium 137) • Pastuerization (70°C, 30 minutes)

26. Alternative Treatments for Class B Biosolids • FC < 2,000,000/gram • PSRPs • Equivalent PSRPs

27. PSRPs • Aerobic Digestion (time and temp requirements) • Air Drying (>3 months, temp >0°C) • Anaerobic Digestion (time and temp requirements) • Composting (≥40°C, five days) • Lime Stabilization (pH12 for two hours of contact)

28. Vector Attraction Reduction • Destruction of organic carbon compounds • Unfavorable environmental conditions • Barrier creation

29. Vector Attraction Reduction Alternatives for EQ biosolids • Biosolids Digestion • Test end-product of anaerobic digestion • Test end-product of aerobic digestion • Aerobic digestion with SOUR teston endproduct • Time/temp requirements for composting • High pH stabilization • Drying • Stabilized • Unstabilized

30. Vector Attraction Reduction for Non-EQ biosolids • Soil injection • Tillage • pH stabilization for septage

31. Metals Cd Cu Pb Hg Mo Ni Zn Metalloid As Non-metal Se Trace Element Content

32. What do risks from trace elements depend on?

33. Binding to Soil • Bio-availability • Concentration

34. Pathways for Risk Assessment • EPA evaluated 14 pathways for high risk individual • Three found to be limiting Limiting pathways • As – ingesting biosolids • Cd – ingesting biosolids • Cu – plant toxicity • Pb – ingesting biosolids • Hg – ingesting biosolids • Mo – livestock feed • Ni – plant toxicity • Se – ingesting biosolids • Zn – plant toxicity

35. Limits on Trace Elements for Land Application • Biosolids meeting low level requirements have no cumulative loading rate restrictions • Most in Washington meet • If one element exceeds limit, then subject to cumulative loading rate restrictions

36. Are biosolids safe to use?

37. What are the limitations on the application of biosolids?

38. What happens if biosolids do not meet land application standards?

39. Incineration • Landfill • Further Treatment • Other