Biosolids Management Utilizing Solar and Thermal Processes

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Geraldine Hood
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1 Biosolids Management Utilizing Solar and Thermal Processes By Chris Enloe-Instrument & Supply, Inc. And Shannon Jones, P.E.-Utilities Engineer City of Fayetteville

2 What are biosolids? Biosolids are the treated finished product from the wastewater treatment process. Billions of bacteria and other microbes thrive in the wastewater facility environment where they consume the organic content from the wastewater stream and continually multiply. To maintain optimum conditions and remove the nutrients absorbed by the microbes, a fraction of the microbial population is regularly removed. Referred to as Waste Activated Sludge (WAS). When treated and processed, sewage sludge becomes biosolids which can be safely recycled and applied as fertilizer to sustainably improve and maintain productive soils and stimulate plant growth.

3 Fayetteville History In 2003, Fayetteville was forced to abandon land application of waste sludge Landfill disposal was readily available and inexpensive By 2008, several area landfills no longer accepted AR solids Landfill costs for those that would still take solids skyrocketed almost 600% Fayetteville wanted a long-term, dependable, and more sustainable solution

4 Why consider drying? Takes waste out of landfill Big volume reduction Beneficially useful product Self reliant If energy is managed, can be lower operating cost AND smaller carbon footprint

5 Class A vs. Class B 40 CFR, Part 503 Class A biosolids contain no detectible levels of pathogens. Class A biosolids meet strict vector attraction reduction requirements and low level metals contents, and generally have unrestricted use. Class B biosolids are treated but still contain detectible levels of pathogens. There are buffer requirements, public access, and crop harvesting restrictions for virtually all forms of Class B biosolids.

6 Alternatives Considered

7 Specific Options Compared

8 Option Selected Combined application of both Solar and Thermal Drying Results in lower capital and operating cost long term

9 Combination Drying Free Bound WAS

10 Drying Sludge Provides Big Volume Reduction Before 100 lbs. Wet After 20 lbs. Dry

11 Beneficially Useful Product Class A Product for Distribution/Sale Stockpile storage - low cost, long life

12 Spreadable bulk fertilizer

First Step-Solar Houses 6 7 1 3 5 2 4 1 Air flap 2 Exhaust fans 3

13 First Step-Solar Houses Air flap 2 Exhaust fans 3 Ceiling fans 4 Electric Mole 5 Inside sensor 6 Outside sensors 7 PLC

14 Thermo-System Active Solar Dryer Fayetteville, AR Biosolids Management Site

15 Typical Solar House Drying Cycle De-watered biosolids are trucked to the site from either WWTP

16 Solids are emptied into the Unload Basin

17 Solids are then loaded into the spreader or hauled directly into the houses with the skid-steer loader

18 Solids are then spread as evenly as possible inside the houses

21 Then the moles are turned loose to do their thing!

23 Mole Video

24 After a variable weather-dependent drying period, the final product is ready for the next step

25 Second Step Thermal Dryer 1 Sludge goes from hopper to drying chamber. 2 Steam to condenser. 3 Dry product to silo. 4 Heated by thermal fluid from heat exchanger

26 Inlet Conveyor

27 Loading product into Thermal Building

28 Feed Conveyor Discharges into Feed Hopper

29 Feed Hopper before initial use

30 Feed Hopper initial fill

31 Screw Conveyors Transport Solids to the Dryer

32 Fenton Fenix Batch Dryer - Indirect Heat

33 Internal Rotating Assembly

34 Heat Exchanger 15,000,000 BTUs

35 Natural Gas - >20,000 cfh capacity

36 Surge Bin allows product to cool

37 Finished product ready for hauling/storage

38 Bulk Storage Silo

39 Performance Solar Houses Target 50% solids before transferring to Thermal Dryer Initial results before thermal dryer completion (summer months) >80% Solids (Class B) 5:1 Volume Reduction 5:1 Weight Reduction Thermal Dryer >90% Solids (Class A) 5:1 Volume Reduction 5:1 Weight Reduction ~60% Reduction in Costs vs. Landfill

41 Biosolids Management Site

42 Project Contributors City of Fayetteville (Design & Construction Management) CH2M HILL (Wastewater Operations) CDM Smith (Biosolids Management Study) McClelland Consulting Engineers (Geotech/Foundation Design) Instrument & Supply (Manufacturer s Representative) Parkson / Thermo-System (Solar Equipment) Fenton Environmental Technologies (Thermal Equipment)

43 Questions?

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