SLUDGE and BIOSOLIDS HANDLING, TREATMENT, DISPOSAL, and MANAGEMENT

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1 SLUDGE and BIOSOLIDS HANDLING, TREATMENT, DISPOSAL, and MANAGEMENT Joseph F. Malina, Jr., Ph.D., P.E., BCEE, D.WRE C.W. Cook Professor in Environmental Engineering Civil, Architectural, & Environmental Engineering Department Cockrell School of Engineering The University of Texas at Austin Presented at the Eckenfelder Lecture Series, Austin, TX 03 June 2014

2 Municipal Wastewater Biosolids and Solid Wastes: Recycling Our Way into the Future Sources and characteristics of biosolids impact treatment, disposal, and management alternatives.

3 Biosolids Management Minimize impact on public health and safety and on the environment Efficient and cost effective Markets for the final products compost, methane gas, etc. Value of final products exceeds the costs of production

4 Costs of Biosolids Processing Collection Pretreatment Construction, equipment, operations energy & labor costs Transport from source to processing facility (pumping or hauling) Processing Land, construction, equipment, operations energy, & labor costs

5 BIOSOLIDS???? What are biosolids??? Sludge??? Biomass??? Food Waste??? Trees, leaves, grass, yard wastes??? Other Organics paper, wood???

6 Biosolids nutrient-rich organic materials resulting from the treatment of domestic sewage in a treatment facility. When treated and processed, these residuals can be recycled and applied as fertilizer to improve and maintain productive soils and stimulate plant growth. Source: EPA FAQ

7 Nutrient Levels in Commercial Fertilizers and Wastewater Sludge Nutrient (%) Nitrogen Phosphorus Potassium Fertilizers for Typical Agricultural Use* Typical Values for Stabilized Municipal Wastewater Sludge *Rates of application vary to reflect soil and crop needs, and the relative concentrations of nutrients in a fertilizer may range up to 82% nitrogen, up to 10% phosphorus, and up to 25% potassium.

8 Characteristics and Quantities of Biosolids in Municipal Wastewater

9 Characteristics of solids and sludge produced in households in non-sewered areas Septic Tank Septage Septage from septic tanks is black and has an offensive odor because of the hydrogen sulfide and other gases.

10 Characteristics of biosolids and sludge produced during municipal wastewater treatment Biosolids or sludge Screenings Grit Scum/grease Primary sludge Activated sludge Trickling-filter sludge Description include organic and inorganic materials large enough to be removed on bar racks (rags). contains heavier inorganic solids that settle rapidly. Specific gravity is greater than 2.0. includes floatables (mainly grease and fat) skimmed from liquid surfaces settling tanks. usually is gray and slimy and usually has an offensive odor. generally has a brownish color, is flocculent in appearance, and has an inoffensive "earthy" odor. Dark sludge may be septic. Humus sludge is brownish, flocculent, and has a relatively inoffensive odor.

11 Characteristics of municipal wastewater solids after treatment Biosolids/ Sludge Digested sludge (aerobic) Digested sludge (anaerobic) Composted biosolids Description Aerobically digested sludge is brown to dark brown and has a flocculent appearance. The odor is not offensive and can be characterized as musty. Anaerobically digested sludge is dark brown to black and contains gas (CH 4 & CO 2 ). Digested sludge drains rapidly. The odor of well-digested sludge is not offensive (resembles garden loam). Composted sludge is dark brown to black. The odor of well-composted sludge is inoffensive an resembles that of commercial garden-type soil conditioners.

12 Municipal Wastewater Treatment Sludge Yield 10,000 people [1 MGD] Primary Solids 1460 lb dry solids/day 5% solids content lb wet sludge/day 3500 gal sludge/day 950 lb volatile solids/day 510 lb fixed solids/day NOTE: Relationship between weight of solids and volume depends on water content. 5 percent sludge contains 95 % water by weight and 5 % solids by weight or 5 lb solids in 100 lb wet sludge Solids fixed (mineral) solids volatile (organic) solids.

13 Municipal Wastewater Treatment Sludge Yield 10,000 people [1 MGD] Excess Activated Sludge 450 lb dry solids/day 1% solids lb wet sludge/day 5396 gal sludge/day 360 lb volatile solids/day 90 lb fixed solids/day Thickened Excess Activated Sludge 425 lb dry solids/day 2% solids lb wet sludge/day (95% solids capture) 2548 gal sludge/day 340 lb volatile solids/day 85 lb fixed solids/day

14 Municipal Wastewater Treatment Sludge Yield 100,000 people [10 MGD] Primary Solids lb dry solids/day 5% solids content lb wet sludge/day gal sludge/day 9500 lb volatile solids/day 5100 lb fixed solids/day

15 Municipal Wastewater Treatment Sludge Yield 100,000 people [10 MGD] Excess Activated Sludge 4500 lb dry solids/day 1% solids lb wet sludge/day gal sludge/day 3600 lb volatile solids/day 900 lb fixed solids/day Thickened Excess Activated Sludge 4250 lb dry solids/day 2% solids lb wet sludge/day (95% solids capture) gal sludge/day 3400 lb volatile solids/day 850 lb fixed solids/day

16 Municipal Wastewater Treatment Sludge Yield 100,000 people [10 MGD] Digested Sludge lb dry solids/day 2.4% solids lb wet sludge/day gal sludge/day 5950 lb volatile solids/day 5950 lb fixed solids/day Methane Produced ft 3 CH E+07 BTU/day

17 Biosolids Primarily organic solid product yielded by municipal wastewater treatment processes that can be beneficially recycled source EPA 40 CFR Part 503 Biosolids Rule

18 The policy of the U.S. EPA dealing with the management of municipal wastewater treatment plant sludge is: "... actively promote those municipal sludge management practices that provide for the beneficial use of sludge while maintaining or improving environmental quality and protecting public health...

19 Municipal Solid Wastes Composition Constituent Composition of commingled Waste people people pounds/day pounds/day Food Wastes Yard Waste Wood Paper & Cardboard Other source: EPA Municipal Solid Waste Generation, Recycle and Disposal in the United States Facts & Figures 2007

20 Solids Stabilization Processes Used by POTWs, % (WEF, 1998) Adv. Thermal Compost. Alk. 4% 4% 4% Aerobic Digestion 8% Other Treatment 11% Lime Stabili 13% Heat Treat. 4% Anaerobic Digestion 52%

21 Background Over 7 million ton of dry municipal sludge solids generated annually in the U.S. Approximately 2.2 million ton of biosolids (primarily Class B) were applied to land in 1998

22 Beneficial Use/Disposal Options for Municipal Sludge Biosolids Land Application Distribution and Marketing Land filling Incineration

23 Constituents in Biosolids Volatile Solids Nutrients (N & P) Pathogenic Organisms Heavy Metals Toxic Organic Chemicals

24 Beneficial Use/Disposal Options for Municipal Sludge Biosolids Relative Importance of Sludge Constituents Constituent Volatile Solids Nutrients (N&P) Pathogens Heavy Metals Toxic Organic Chemicals Land Application Moderately Important Very Important Very Important Very Important Moderately Important Distribution and Marketing Moderately Important Moderately Important Very important Very Important Moderately Important Landfilling Moderately Important Moderately Important Not Important Moderately Important Moderately Important Incineration Very Important Not Important Not Important Moderately Important Moderately Important

25 Typical Pathogens in Untreated and Anaerobically Digested Sludge Pathogen Typical concentration in untreated sludge (Number /100 milliliters) Typical concentration in anaerobically digested sludge (Number /100 milliliters) Virus 2,50-70, ,000 Fecal Coliform Bacteria* 1,000,000,000 30,000-6,000,000 Salmonella 8, Ascaris lumbricoides 200-1, ,000 *normally not pathogenic, frequently used as indicator organism.

26 Municipal Wastewater Sludge Biosolids Important Physical and Chemical Characteristics water content, degree of stabilization, and ph

27 Water content affects: Size of treatment and disposal facilities, Transportation costs, Type of land application equipment used, Amount of auxiliary fuel needed to evaporate water during incineration, Size and life span of a sludge landfill (monofill), and Leachate formation in landfills.

28 Organic content (Volatile Solids)) putrescibility and potential for odor problems in sludge storage and land application; value as a soil conditioner in land application; and potential for gas generation (in anaerobic digestion) heat value of sludge that is important in designing incineration systems;

29 Primary Sludge Excess Activated Sludge Gravity Thickener Dissolve Air Flotation Anaerobic Digestion Land Disposal Composting Belt Thickener Ae robic Digestion Ocean Disposal Sludge Dis pos al Alternative - Biological Treatment and Land Dis pos al

30 Anaerobic Sludge Digestion

31 The principal advantages of anaerobic sludge digestion include: digester gas contains methane - usable energy that can be used to maintain temperature of the digesting sludge, heat buildings, drive the engines for the aeration blowers, Approximately 25-45% (weight basis) of the influent sludge solids are destroyed - reducing the mass and volume of sludge requiring disposal digested sludge is soil conditioner & contains N and P, other nutrient and stable organic matter pathogens and parasite ova associated with the raw sludge are inactivated during anaerobic digestion.

32 The principal disadvantages of anaerobic sludge digestion are: capital costs are high. Large covered tanks pumps for introducing raw sludge and circulating digesting sludge, heat exchangers and gas compressor(s) or pump(s) for mixing. hydraulic detention time = 15 days is required by 40 CFR Section 503 Sludge Regulations Supernatant from anaerobic digestion contains suspended solids, oxygen consuming compounds (BOD), nitrogen, and phosphorus.

33 Volatile Solids 70 kg Volatile Solids converted to Methane & Carbon Dioxide Mixture of Primary Solids & Waste Activated Sludge Dry solids = 100 kg Volatile solids = 70% Fixed Solids 30 kg Volatile Solids 30 kg Fixed Solids 30 kg Anaerobically Digested Sludge Dry Solids = 60 kg Volatile Solids = 50%

34 Gas production 12 to 16 ft 3 of gas ft/lb VS destroyed methane content of the gas is 60 to 75% by volume energy content of the digester gas = 600 to 750 BTU per cubic foot. [energy content of methane is 1000 BTU/ft 3 ] gas production rate of 15 ft 3 /lb VS destroyed and a methane content of 67%, yields approximately 10,000 BTU per pound of volatile solids destroyed.

35 Digester Gas CO 2 Removal Anaerobic Digestion H 2 S Removal Raw Sludge Boiler Heat Exchanger Hot Water Cooling Water Flare Mechanical/ Electrical Power Diesel Fuel

43 AEROBIC SLUDGE DIGESTION

44 Advantages claimed for aerobic digestion low capital costs for plants under 5 MGD (220 L/s) relatively easy to operate process nuisance odors are minimal volatile solids destruction is approximately equal to that observed in anaerobic digestion as long as the ratio of primary solids to biological solids is less than supernatant contains low concentrations of BOD 5, suspended solids, and ammonia nitrogen end product is humus-like, odorless, and biologically stable pathogens reductions are high under normal design. autothermal thermophilic digestion results 100 percent pathogen destruction

45 Disadvantages reported for aerobic digestion processes are: poor mechanical dewatering characteristics of the aerobically digested sludge. high power costs to supply oxygen, even for very small plants. performance is affected by type of sludge, temperature, location, and type of tank material.

49 Summary of Aerobic Sludge Digestion Design Criteria) ( Operating Temperature = 20 O C [68 O F]) Hydraulic detention time required Excess Activated Sludge only following primary sedimentation Activated Sludge without primary sedimentation Excess Activated Sludge with primary sludge days days days Trickling Filter Humus plus primary sludge days Influent Solids Concentration Excess Activated Sludge only (Prim + EAS) Oxygen Requirements Includes nitrification Nitrification is inhibited at high temperatures 0.8 to to Minimum Dissolved Oxygen in Digester 1.0 to 2.0 mg/l Energy Requirements for Mixing is Controlled by % % lb O 2 / lb VS Destroyed (T <113 O F) (T >113 O F) 0.75 to 1.50 hp/1000 ft 3

50 Baffle Plate Air Lines Control Baffle Supernatant Drawoff Sludge Concentration Chamber Return Sludge Air-Lift Pump Influent Sludge Air-Lift Pump and Draft Tube Digested Sludge Drawoff Circular Aerobic Digester

51 Raw Sludge 110ÞF 3-5 days 135ÞF 3-5 days 10 days Pump Thickener Autothermal Thermophilic Aerobic Digesters Sump Digested Sludge Storage Typical Autothermal ThermophilicAerobic Digestion System

52 Design Parameters for Autothermal Thermophilic Aerobic Digestion Reactors Sludge type Pretreatment requirements Influent solids conc n (4% to 6%) Req d Vol Sol conc n 65 % Detention time Two (2) or more stages of equal volume operating in series Primary solids, excess activated sludge, trickling filter humus) Efficient grit removal and sludge thickening to concentrate solids 5 to 6 days Temperature and ph Reactor 1: T = 95 O F to 122 O F, ph ~7.2 Reactor 2: T = 122 O F to 149 O F, ph ~ 8.0 Air input Energy Requirement Heat potential for recovery 4 m 3 /hr/m 3 of active reactor volume 9 to 15 kwh/m 3 of sludge 23 to 30 kwh/m 3 of sludge

53 Sludge/Sludge Heat Exchanger Water/ Sludge Auxiliary Heat Exchange Raw Sludge Thickener Pump 150ÞF 24 hours 98 ÞF 15 days Thermophilic Aerobic Digester Mesophilic Anaerobic Digester Digested Sludge Storage Typical Pre-Stage Aerobic Thermophilic Digestion/ Anaerobic Digestion System

54 Sludge Composting

55 Sludge Composting Systems Objectives aerobic decomposition of sludge to produce a humus-like product resembling soil. typically composted for 21 to 30 days,. during which time pile temperatures typically reach 55 o C in a properly run operation

56 Ame ndm ent Odor Treatme nt & Dispersion Sludge Mixing a nd conve ying sy ste m Reac tor Sy stem Curing/ Stora ge Distribution/ Ma rketing Recy cle Air Supply Sy stem

57 Aerobic Composting Operating Parameters oxygen availability within the compost, moisture content (50 60%) Temperature (55-60 o C) and biodegradable volatile solids content of the compost.

58 Compost Systems Windrow, static piles, and In-vessel composting systems.

71 Compost Windrow

82 The minimum required detention time in Windrow Composting is a function of: type of feed sludge, e.g. raw or digested, primary sludge or biosolids, mixture of primary sludge or biosolids processes used for high-rate digestion and curing types of amendments used ability to maintain aerobic conditions, end use of the product.

83 Detention Time detention time 60 days should be adequate for most composting systems and end product uses. high rate digestion period usual is 10 to 20 days aging or curing process extends the total detention time to 60 days.

84 Air Requirements satisfy oxygen demands of biodegradation of the organic constituents, remove moisture from and dry the composting sludge and amendments and remove heat generated to control process temperatures.

85 Aeration Rates minimum aeration rates for an individual pile or windrow occur at the very beginning of the batch cycle and may be as low as 200 to 500 scfh/dry ton day aeration rates for a continuous feed process is approximately 43.0 lb of air / lb of dry sludge (47,900 scfh / dry ton - day of sludge. maximum sustainable aeration rates range between 40,000 to 60,000 scfh/dry ton - day of sludge for an autogenous raw sludge with recycle of the composted mixture in a continuous feed, complete mix reactor.

86 Odor Control diluting odorous air with outside air, bubbling the odorous air through water at an adjacent wastewater treatment plant passing the odorous air through a soil and/or compost biofilter, one- or two-stage wet chemical scrubbers (sulfuric acid, sodium hypochlorite, sodium hydroxide and various proprietary chemicals). Chemicals typically used in the scrubbers include sulfuric acid, sodium hypochlorite, sodium hydroxide and various proprietary chemicals.

87 Food Wastes Presorted Grocery Wastes (produce, meat, dairy, etc. Food scraps (slop) from prisons Off-Spec, Out-of-Date Beverages (including containerized and bulk soft drinks, fruit drinks, beer, wine, etc.) Dairy Materials (milk/milk byproducts)

90 Other Organic Wastes Yard Trimmings (brush, lawn clippings, etc.) Untreated, Unpainted Lumber, Pallets, etc. Paper (phone directories, cardboard, shredded office paper) Manure Dairy Products Solid & Liquid Food Residuals Other Vegetative Liquids

94 Conditioni ng Primary Sludge Excess Activate d Sl udge Gravity Thickener Dissolve Air Flotation Belt Thickener Filte r Press Vacuum Filte r Belt Filter Landfill Incineratio n Centrif uge S ludge Dis pos al Alternative - Dewatering and I ncineration

95 Primary Sludge Excess Activate d Sl udge Gravity Thickener Dissolve Air Flot ation Belt Thickener Com posting Wet Air Oxidation Pyrolysis Ve rm acult ure Composting and Nove l Sludge Disposal Alte rnatives

96 SLUDGE REGULATIONS Criteria for assessing sludge stabilization are not universally accepted. Definitions of sludge stabilization are qualitative and descriptive. Stabilization processes usually result in the: elimination of offensive odors; destruction of organic material and in this way eliminate or inhibit the potential for further biodegradation; reduction in the number of pathogens in the sludge; and production of a sludge which can be disposed of without environmental or ecological damage or nuisance (unsightly condition, flies, other vermin, etc.).

97 Criteria for Reduction in the Number of Pathogens Class A, Municipal Wastewater Sludge Class A Pathogenic bacteria, viruses, protozoa and helminth ova below detectable level or Sludge heated to 53 C for 5 days or Sludge heated to 55 C for 3 days or Sludge heated to 70 C for 0.5 hours and Density of Fecal coliform < 10 3 per g TS

98 Criteria for Reduction in the Number of Pathogens Class B, and C Municipal Wastewater Sludge Class B Density of pathogenic bacteria and viruses per gram of volatile suspended solids is 100 times less in sludge than in the influent wastewater or Density of Fecal coliform < 2x10 6 per g TS Class C Density of pathogenic bacteria and viruses per gram of volatile suspended solids is 31.6 times less in sludge than in the influent wastewater or Density of fecal coliforms and fecal streptococci is less than or equal to per gram VSS

99 Processes to Significantly Reduce Pathogens (two-log reduction in numbers of indicators organism) Aerobic Digestion Air Drying Anaerobic Digestion 60 days digestion time at 15 C (59 F) or 40 days digestion time at 20 C (68 F) > 38% volatile solids reduction Drainage and/or drying of sludge on sand beds or in paved or unpaved basins with maximum depth of sludge of 9 inches minimum time three (3) months with two (2) months when average daily temperature is above 0 C (32 F) 60 days digestion time at 20 C (68 F) or 15 days digestion time at 35 C (95 F) to 55 C (131 F) > 38% volatile solids reduction

100 Processes to Significantly Reduce Pathogens (Continued) (two-log reduction in numbers of indicators organism) Composting in-vessel, static aerated pile, windrow minimum temperature of 40 F (105 F) temperature must be maintained at 55 C (131 F) for at least four (4) hours Lime Stabilization ph must be maintained at ph = 12 for two (2) hours

101 Processes to Further Reduce Pathogens Composting in-vessel and static pile : temperature > 55 C for at least three (3) days windrow temperature > 55 C for at least fifteen (15) days and at least five (5) turnings during high temperature period Heat Drying Heat Treatment sludge cake is dried with hot gases to a moisture content of 10% or less temperature > 80 C in sludge particle or in steam (wet bulb) leaving the dryer temperature > 180 C (356 F) for 30 minutes Thermophilic Aerobic 10 days digestion time at 55 C (131 F) to 60 C Digestion (140 F), > 38% volatile solids reduction Other Technologies if pathogens and volatile solids are reduced to equivalent extent as above technologies

102 Processes to Further Reduce Pathogens Following Process to Significantly Reduce Pathogens Beta Ray Irradiation Gamma Ray Irradiation beta ray dosage required is 1.0 megarad at approximately 20 C (68 F) gamma rays from Cobalt 60 or Cesium 139 dosage required is 1.0 megarad at approximately 20 C (68 F) Pasteurization minimum temperature required is 70 C 158 F) for at least 30 minutes Other Technologies if pathogens and volatile solids are reduced to equivalent extent as above add-on technologies

103 Sludge Disposal/Management Technologies Stabilization Requirements Land Application Food Chain Crop Production Land Dedicated to Sludge Disposal Landfill Unstabilized sludge only 2-log reduction in indicator organisms total elimination of pathogens for crops for direct human consumption stabilization to minimize odors Stabilization required prior to disposal to minimize odor and potential nuisance conditions Stabilization required prior to disposal to minimize odor and potential nuisance conditions (area fill mound, area fill layer and diked containment) Trench methods and sludge-refuse codisposal

104 Environmental Impacts Associated with the Material Life Cycle in Alternative Processing of Municipal Biosolids greenhouse gas sources and sinks, greenhouse gas emission energy offsets

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107 Transportation Pumping or Hauling Requires energy and is a source of Greenhouse gases

108 Composting Composting of food wastes, paper and cardboard and yard wastes results in production of compost which is a soil conditioner. When compost is applied to land the carbon is stored in the soil (Sink & Emission Offset); however, carbon dioxide is released and contributes to greenhouse gas emissions

109 Incineration Incineration of biosolids) reduces use of fossil fuels (Sink) to provide energy; The products of incineration are Nitrogen Oxide and Carbon Dioxide gases which contribute to Greenhouse gas emissions

110 Land Filling During the life of a landfill and after closure carbon is in long-term storage in the landfill (Sink). Uncontrolled methane (CH 4 ) emissions or flaring CH 4 resulting in the release of CO 2 contribute to greenhouse gas emissions. Converting the CH 4 to energy that is recovered for use reduces use of fossil fuels (Sink) to provide energy

111 SLUDGE REGULATIONS Criteria for assessing sludge stabilization are not universally accepted. Definitions of sludge stabilization are qualitative and descriptive. Stabilization processes usually result in the: elimination of offensive odors; destruction of organic material and in this way eliminate or inhibit the potential for further biodegradation; reduction in the number of pathogens in the sludge; and production of a sludge which can be disposed of without environmental or ecological damage or nuisance (unsightly condition, flies, other vermin, etc.).

WASTEWATER TREATMENT

WASTEWATER TREATMENT Every community produces both liquid and solid wastes. The liquid portion-wastewater-is essentially the water supply of the community after it has been fouled by a variety of uses.