SLUDGE or WATER TREATMENT RESIDUALS u Screenings u
- Slides: 20
SLUDGE or WATER TREATMENT RESIDUALS u Screenings u Grit u Scum u Solids u Biosolids • Substances responsible for offensive character of wastewater • Highly organic in nature • Pathogenic • High water content Reduce water content, organic content and render solids suitable for reuse or final disposal
Sludge Management and Disposal u Thickening, Conditioning – gravity, flotation u Dewatering, Drying Reduce volume by reducing water content – Vacuum filtration, centrifugation, pressure filtration u Digestion, Composting, Stabilization – aerobic, anaerobic, alkaline treatment Reduce organic content/pathogens u Disposal – land application, burial, incineration FINAL DISPOSAL
REGULATIONS u 40 CFR 503 – Uses BIOSOLIDS instead of Sludge when put into beneficial reuse – Land application of biosolids (Class A and Class B) – Surface disposal – Pathogen and vector reduction – Incineration
Volume Mass Relationships Specific Gravity and Volume of Solids Specific gravity of solids Vs = Ws/Ss*ƿ
Volume Mass Relationships Specific Gravity and Volume of Sludge Specific gravity of solids
THICKENING u Increase the solids content of sludge by removing a portion of the liquid fraction u Activated sludge 0. 8% to 4% results in fivefold decrease in sludge volume u Settling, flotation, centrifugation, gravity belt, rotary drum
Sludge Dewatering u Sludge drying beds – historically the most common – sand bed, 15 -30 days, evaporation & seepage u Vacuum Filtration – cylindrical rotating drum covered with fabric – submerged with applied vacuum u Continuous belt filter presses (follows) u Plate pressure filters – vertical plates mounted on a frame
Belt Filter Press: Description In the belt press process, chemical conditioned sludge is resting on a gravity drainage section so that it can be thicken. Water is able to fall from the sludge by the force of gravity. Now pressure is being applied in a low pressure section, where the sludge is squeezed between opposing porous cloth belts. Next it will travel through a high pressure section, where the sludge is subjected to a shear force as the belts pass through a series of rollers. This shearing force and squeezing process reduces additional quantities of water from the sludge. Finally dewatered sludge cake is removed from the belts by scraper blades.
Belt Filter Press
Sludge Volume Reduction A. Start with 1 liter of 1% by weight (i. e. , 10 g/L) sludge. Mass of sludge = (1 liter)(1000 g/L) = 1000 g sludge Mass of solids = (1 liter)(10 g/L) = 10 g dry sludge solids Mass of water = 1000 g - 10 g = 990 g H 2 O B. Gravity Thicken to 4% dry solids (i. e. , 40 g/L). Mass of sludge = (10 g)/(0. 04) = 250 g sludge Mass of solids = unchanged = 10 g dry sludge solids Volume Removed = (1000 m. L - 250 m. L)/1000 m. L = 75% Mass of water = 250 g - 10 g =240 g H 2 O C. Vacuum Filter to 30% dry solids (i. e. , 300 g/L). Mass of sludge = (10 g)/(0. 30) = 33. 3 g sludge Mass of solids = unchanged = 10 g dry sludge solids Volume Removed = (1000 m. L - 33. 3 m. L)/1000 m. L = 96. 7% Mass of water = 33. 3 g - 10 g = 23. 3 g H 2 O
MASS BALANCE for Thickening V 1 = P 1 V 2 P 2 V = volume of sludge P = percent solids in sludge
Anaerobic Digestor 12 -20 days of aeration ~50% reduction in solids
Digester
Anaerobic Digestion • Sludge held without aeration for 10 -90 days • Process can be accelerated by heating to 35 -40 o. C • These are called High Rate Digestors (10 -20 days) • Advantages • low solids production • useable methane gas produced • Disadvantages • high capital costs • susceptibility to shocks and overloads
Conventional standard rate single-stage High rate Completely mixed single-stage Two-stage Process
Process Microbiology Lipids, Proteins, Nucleic Acids, Polysaccharides Hydrolysis Fatty Acids, Amino Acids, Monosaccharides etc Acidogenesis Acid formers Alcohols, hydrogen, CO 2, formate, acetate Methane and Carbon Dioxide Methanogenesis Methane formers
Process Microbiology Methanogens or Methane Formers 4 H 2 + CO 2 = CH 4 + 2 H 2 O 4 HCOOH =CH 4 + 2 H 2 O + 3 CO 2 CH 3 COOH = CH 4 + CO 2 CH 3 OH = 3 CH 4 + CO 2 + 2 H 2 O 4(CH 3)3 N + H 2 O = 9 CH 4 +3 CO 2 + 6 H 2 O+ 4 NH 3 p. H 6. 6 -7. 6, alkalinity should be present; slow growth rates Y =0. 06
Digester Design u Mean Cell Residence Time u Volumetric Loading Factor u Observed Volume Reduction u Loading Factors Based on Populations
Toxics in Municipal Sludge Problem with buildup of heavy metals in soil receiving sludge
Ultimate Sludge Disposal
- Sludge treatment
- Water and water and water water
- How to find standard deviation of residuals
- Section 10 topic 5 residuals and residual plots
- Participations and residuals
- Schoenfeld residuals spss
- Studentized residuals stata
- Lesson 15 interpreting residuals from a line
- What is residual alkalinity
- Activated sludge process flow chart
- Flight sludge collector
- Sludge dumbbells
- Secondary wastewater treatment
- Activated sludge process
- Sludge press
- Epesár
- Sludge density index formula
- Hydrops galblaas
- Wastewater sludge
- Sludge drying beds
- Ekoremediacije