potential benefits, considerations and challenges with

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Potential Benefits, Considerations and Challenges with Composting WWTP Solids/Biosolids on Guam Executive Summary

The Guam Waterworks Authority currently produces 8,200 to 9,000 tons per year of dewatered primary sludge from its wastewater treatment plants (WWTPs), both from the large Northern District Wastewater Treatment Plant (NDWWTP) on the northern part of Guam Island and other smaller plants. This material is trucked to the Layon Landfill at the southern end of the island, about 25 miles away, and disposed of at a current overall cost (hauling and landfilling) of $182 per ton (/ton). Due to increasing population growth and regulatory-required WWTP upgrades, the amount of wastewater sludge is projected to increase to about 14,200 tons per year by 2025. The current plan is to continue landfilling these solids. One potential option to divert WWTP sludge from the landfill is to recycle this material via composting and produce a valuable end-product with diverse uses.

Potential benefits of recycling WWTP sludge through composting include the following:

• Reducing the amount of materials being landfilled by 10% or more thus extending landfill life

• Recycling other waste stream materials such as yard wastes, brush, land clearing debris, broken wood pallets, and other relatively “clean” waste materials for use as needed bulking agent

• Increasing the island recycling rate to help achieve zero waste plan recycling goals

• Producing a valuable fertilizer/soil amendment product(s) that can generate revenue and be used instead of importing similar products from off-island

• Providing Guam’s Department of Defense (DoD) neighbors a possible means to claim green credits for beneficial reuse of organics

• Providing opportunities for private enterprises to conduct the composting and use of the compost products

• Providing potential savings in capital and operations and maintenance (O&M) costs compared to treating sludge through future planned digestion facilities and continued landfilling of the residue

Challenges associated with development of a composting operation include the following:

• Siting of a facility • Selection of an appropriate technology at a reasonable cost • Ownership and operating decisions • Marketing of the product • Proper education of compost users

These challenges can all be addressed with adequate planning and evaluation. Composting the WWTP sludge can truly become a sustainable solution to manage a significant portion of the entire waste stream.

An assessment was conducted to determine the effect on the landfill tip fee if the WWTP sludge were diverted from the landfill. A conservative assumption would be that the overall revenues need to be maintained at their current level, which would require the tip fee to increase by about 9 percent from $172/ton to $188/ton. This is the most conservative scenario and does not consider operational savings at the landfill for having to handle and process up to 9,000 fewer incoming tons. Such operational savings may offset the loss in tipping fee revenue. Additional economic analysis would be needed to confirm this.

Another option is to leave the current level of biosolids disposal the same and divert only the additional quantity of dewatered solids that are produced in the future to composting. This option would maintain the current overall landfill revenue stream and would not impact the tipping fee. This scenario would allow for overall system costs to be fully evaluated prior to further compost facility expansion.

Potential Benefits, Considerations and Challenges with Composting WWTP

Solids/Biosolids on Guam

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A pilot study is recommended to demonstrate the composting process to all stakeholders, including utilities staff, regulatory agencies, politicians and potential product users. Such a study could be accomplished in less than a year using sludge and bulking agent waste materials produced on Guam. The resultant product would be tested and could be used for plant-growing studies at the University of Guam, as well as by other large potential users. Data from the pilot study, sizing analysis, and facility construction and operations cost estimates could then be used for further economic analysis to confirm financial sustainability.

Wastewater Solids Production

The NDWWTP, which is owned and operated by the Guam Waterworks Authority (GWA), is located in Dededo on the northwestern coast of Guam, just inland of the Tranguisson Beach area and north of the Two Lovers Point landmark. The NDWWTP was built by the U.S. Navy and was commissioned in 1979. The facility collects and treats wastewater from the regions of Dededo, Latte Heights, Perez Acres, Ypaopao, Marianas Terrace, the Yigo Collector System, and other unincorporated subdivisions throughout the Yigo and Dededo municipalities. The service area includes U.S. military facilities, including Air Force and Navy facilities within the areas of Dededo, Harmon Annex, and Andersen Air Force Base. The NDWWTP currently provides chemically enhanced primary treatment for a population of approximately 76,000 people. GWA operates four other WWTPs on the Island and the Navy operates one.

Current Production and Quality

The current solids handling operations at the NDWWTP do not include solids stabilization. Instead, the primary sludge generated is dewatered onsite by centrifuges to approximately 31 percent solids and the dewatered sludge is hauled to Layon Landfill via truck for disposal. Sludge drying beds onsite at the NDWWTP are used for emergency sludge dewatering and storage. The current requirement for sludge disposal to the Layon Landfill is that the material is non-hazardous (passes the Toxic Characteristics Leachate Procedure test) and meets the paint filter test (40 Code of Federal Regulations [CFR] 258.28). It is assumed that these two requirements have been met and continue to be met, although no data has been reviewed to validate this assumption. Further, because no sludge stabilization is required to landfill, testing of the sludge for metal content and nutrient content (which is normally required for any land application of treated sludge [biosolids]) is not needed and to our knowledge has not been performed. The total annual quantity of dewatered sludge that has been landfilled at the Layon Landfill over the past 5 years, according to the most recent Quarterly Report of the Receiver (Gershman, 2017), is shown in Table ES-1. The amounts shown are from a combination of all the WWTPs on the island, but the NDWWTP produces the majority of the sludge (approximately 60 percent of the total).

Table ES-1. Tonnages of Dewatered Sludge Landfilled in Layon Landfill by Year

Year 2013 2014 2015 2016 2017 Average

Estimated Tonnage 7,470 9,350 6,180 9,100 8,750 8,170

Notes:

Tonnages (wet tons) shown are based on data available in the above referenced quarterly report, which only summarized quantities from January to June each year in Table 3 of that report. The annual quantity has been estimated by doubling these quantities.

Source: Gershman, 2017

Future Production and Quality

Future wastewater flows are expected to increase due to the relocation of the U.S. Marine Corps to Guam from Okinawa, the related support construction activities associated with that relocation, increases in tourism, and a permit-driven upgrade to the WWTP process to provide secondary treatment, all within the next 4 to 6 years. The current NDWWTP solids handling system is not adequate to handle future

Potential Benefits, Considerations and Challenges with Composting WWTP Solids/Biosolids on Guam

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projected wastewater flows and loads. As a result, an upgrade of the solids processing system is being designed and an increased production of dewatered cake at a lower solids content is expected.

Based on the preliminary design of these upgrades as outlined in the CH2M HILL (CH2M) (now Jacobs Engineering Group Inc. [Jacobs]), April 19, 2018, Pre-Design Solids Process Alternative Analysis

technical memorandum (CH2M, 2018) submitted to and accepted by the GWA, the projected average annual sludge quantity that will be produced once the Phase I planned WWTP upgrades are completed is estimated to be 14,200 wet tons in 2025 (raw sludge alternative – not digested). This quantity represents approximately a 75 percent increase in sludge cake production over current loading to the landfill, or an additional 6,000 wet tons annually that is planned to be landfilled beginning in 2025 or sooner. In addition, the characteristics of these solids will change. The existing primary solids are dewatered to approximately 31 percent solids content and likely contain about 80 percent volatile solids. The secondary solids that will be produced after the upgrade will have a slightly lower volatile solids content and will be dewatered to only 20 percent solids content on average. The ultimate build-out is expected to produce 18,000 wet tons of dewatered solids by 2065 (raw sludge alternative) unless the additional stabilization option of autothermal anaerobic digestion is added in a possible Phase II upgrade.

Figure ES-1. Projected Tonnage of WWTP Sludge Produced

1. Background of Composting WWTP Residuals/Biosolids

Composting of WWTP solids has been practiced by hundreds of municipalities for decades as an acceptable process to produce a Class A Exceptional Quality Biosolids product as defined by the U.S. Environmental Protection Agency (USEPA). The process allows treatment of dewatered sludge or biosolids from WWTPs to produce a soil-like humus product with a wide range of uses. Typically, an amendment or bulking agent such as ground yard wastes or wood chips are added to the dewatered solids in approximately a 1:1 weight ratio to achieve the appropriate solids content and porosity to allow composting to occur in a controlled aerobic process.

Figure 1. Site Location Potential Benefits, Drawbacks and Challenges with

Composting WWTP Solids/Biosolids on Guam

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31.5 km

28.8 km

27.9 km

Agat/Santa Rita WWTP

North District WWTP

Lanyon Landfill

Baza Gardens STP

E

Apra Harbor WWTPNaval Base Guam

Agana/ Hagatna STP

Umatac-Merizo WWTP


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1.1 Composting Definition

According to Dr. Eliot Epstein, one of the recognized grandfathers of developing the technology, “Composting is a process that involves the biological decomposition of organic matter under controlled, aerobic conditions into a humus-like stable product” (Epstein, 1997). Because the process is controlled to be aerobic and is biological, heat is generated by the microbial population, which results in the process operating in the thermophilic temperature range for an appropriate length of time to destroy pathogenic organisms. The major objectives associated with composting as defined by Dr. Epstein are to do the following:

• Decompose potentially putrescible organic matter into a stable state to produce a material with reduced odor that can be safely stored and used for soil improvement or other beneficial uses.

• Disinfect pathogenically infected organic wastes so that they may be beneficially used in a safe manner.

When composting WWTP sludges or biosolids there are four major objectives:

1) Kill disease-causing organisms (reduce pathogens). 2) Further stabilize biosolids by decomposing odor-producing compounds. 3) Dry the biosolids. 4) Produce a stable, manageable, and marketable product.

The product produced from composting is also defined as follows by the U.S. Composting Council (2018):

Compost is the product manufactured through the controlled aerobic, biological decomposition of biodegradable materials. The product has undergone mesophilic and thermophilic temperatures, which significantly reduces the viability of pathogens and weed seeds, and stabilizes the carbon such that it is beneficial to plant growth. Compost is typically used as a soil amendment but may also contribute plant nutrients.

1.2 Reasons for Interest in Composting

The composting process has been practiced for many decades and is recognized as a well-established technology for managing wastewater solids and producing a high-quality compost product that has a wide range of potential uses. There are many reasons for interest in composting of WWTP residuals today, with some of the main reasons for this interest as follows:

• The process allows for sustainable and beneficial use of biosolids.

• There are increasing uncertainties with land application of biosolids.

• There is incompatibility of landfilling sludge/biosolids due to decreasing capacity and increasing tipping fees.

• The process is able to effectively co-manage biosolids with other waste streams such as yard wastes, wood wastes, and source separated food wastes.

• Recent advances in composting technologies have allowed for optimal process control and odor control, making the process more feasible and acceptable to neighboring property owners.

• The process produces a Class A – Exceptional Quality Biosolids Product per the USEPA.

• The process produces a highly marketable and valuable product that is nutrient-rich, with diverse uses.

• The economics are favorable compared to other technologies.

• There is increasing involvement of private companies to finance, own, and operate compost facilities.



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1.3 Experience in Composting Wastewater Solids

In 1973, the U.S. Department of Agriculture (USDA) initiated a significant research effort into composting of wastewater sludge; from that research, basic engineering and process aspects, pathogen and bioaerosol studies, plant growth studies, heavy metal uptake and microbiological studies were accomplished. Much of this data was used by the USEPA in developing the 40 CFR 257 regulations on the process of composting wastewater sludge. Many different composting methods have emerged in the past 50 years, all with the ability to produce a high-quality compost product. Figure 2 shows the increase in biosolids composting facilities in the U.S. and across North America. Today, over 260 active biosolids composting facilities operate in 44 states, Canada, and Puerto Rico. These facilities compost over 3 million tons of dewatered biosolids annually and produce over 7.5 million cubic yards of high quality saleable compost products.

A wide range of composting methods and technologies are available that can be used to actively compost sludge, biosolids, food and other organic wastes. Table 1 lists the various technology types in use today. Descriptions of the most common active composting methods/technologies are provided in other reference textbooks, such as Solids Process Design and Management (Water Environment Federation, 2012) and the Environment Canada Technical Document on Municipal Solid Waste Organics Processing (2013).

Table 1. Classification of Composting Methods and Systems

Passively Aerated Actively Aerated

Static Pile (unaerated)

Bunkers

Turned Windrow

Turned Mass Bed

Passively Aerated Windrow

Aerated Static Pile (ASP)

Membrane Covered Aerated Static Pile

Channels

Turned and Aerated Mass Bed

Agitated Bed

Static Containerized Systems

Agitated Containerized Systems

Tunnel Systems

Figure 2. Numbers of Biosolids Composting Facilities in the U.S. reported by Beecher and Goldstein Source: Goldstein, 2010


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1.4 Regulatory Framework

The USEPA requires that the biosolids compost meet strict criteria and achieve low pathogens and metals concentrations to allow unrestricted end use applications such as to lawn and gardens, construction projects, land reclamation projects, and athletic fields. Current regulations state that compost pile temperature must be maintained at 55 degrees Celsius (°C) (131 degrees Fahrenheit [°F]) or higher for 3 consecutive days to reduce pathogen densities to below detectable limits for salmonella and fecal coliform. In addition, temperatures must be maintained higher than 40°C (104°F) for 14 consecutive days, with an average temperature higher than 45°C (113°F) to further stabilize the material and reduce the potential for spreading infectious disease through vectors such as flies. The compost produced must also be below acceptable metals concentrations as defined in 40 CFR Part 503.

Composting of sewage sludge by definition creates a Class A EQ Biosolids compost product as long as the three requirements listed below are met. Each of these three requirements for composting are further described in the following. EQ biosolids compost may be land applied without site restrictions.

Exceptional quality (EQ) biosolids are biosolids which have:

1) Met the USEPA Part 503 pollutant concentration limits (Table 3 of Section 503.13)

2) Met the Class A pathogen reduction requirements of one of the processes as defined in Appendix B under Processes to Further Reduce Pathogens (PFRP)

3) Met one of the first eight vector attraction reduction options listed in 503.33(b)(1) through (b)(8)

1.4.1 §503.13 Pollutant Limits

The USEPA §503.13 pollutant limits state the following:

(a) Sewage sludge.

(1) Bulk sewage sludge or sewage sludge sold or given away in a bag or other container shall not be applied to the land if the concentration of any pollutant in the sewage sludge exceeds the ceiling concentration for the pollutant in [Table 2 (taken from Table 3 of §503.13)].

Table 2. Pollutant Concentrations

Pollutant

Monthly average concentrations

(milligrams per kilogram)1

Arsenic 41

Cadmium 39

Chromium 1200

Copper 1500

Lead 300

Mercury 17

Molybdenum 18

Nickel 420

Selenium 36

Zinc 2800

1 Dry weight basis. Source: Table 3 of §503.13 (40 CFR 503)



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1.4.2 Class A Pathogen Reduction Requirements

The use of USEPA PFRP [503.32(a)(7)] Alternative 5 provides continuity with the 40 CFR 257 regulation. This alternative states that sewage sludge is considered to be Class A in the following case:

• It has been treated in one of the PFRPs listed in Appendix B of the regulation, and

• Either the density of fecal coliforms in the sewage sludge is less than 1,000 MPN per gram total solids (dry weight basis), or the density of Salmonella sp. bacteria in the sewage sludge is less than 3 MPN per 4 grams total solids (dry weight basis) at the time the sewage sludge is used or disposed, at the time the sewage sludge is prepared for sale or give away in a bag or other container for land application, or at the time the sewage sludge or material derived from the sewage sludge is prepared to meet the requirements in 503.10(b), 503.10(c), 503.10(e), or 503.10(f).

PFRPs are listed in Appendix B of 40 CFR 503. There are seven PFRP processes: composting, heat drying, heat treatment, thermophilic aerobic digestion, beta ray irradiation, gamma ray irradiation, and pasteurization. When these processes are operated under the conditions specified in Appendix B, pathogenic bacteria, enteric viruses, and viable helminth ova are reduced to below detectable levels.

The composting conditions required are as follows: Composting using either the within-vessel composting method or the static aerated pile composting method, the temperature of sewage sludge is maintained at 55°C (131°F) or higher for 3 consecutive days. Using the windrow composting method, the temperature of the sewage sludge is maintained at 55°C (131°F) or higher for 15 consecutive days or longer. During the period when the compost is maintained at 55°C (131°F) or higher, there shall be a minimum of five turnings of the windrow.

1.4.3 Vector Attraction Reduction Requirements

For Option 5 - 503.33(b)(5), aerobic treatment of the sewage sludge for at least 14 days at over 40°C (104°F) with an average temperature of over 45°C (113°F) is typically accomplished during biosolids composting, which therefore complies with this requirement.

1.5 Compost Product Benefits

The Association of American Plant Food Control Officials (AAPFCO) and the United States Composting Council (USCC) have established the following verified benefits of compost when used as a soil amendment (USCC, 2018):

1) Improves soil structure and porosity – creating a better plant root environment

2) Increases moisture infiltration and permeability, and reduces bulk density of heavy soils – improving moisture infiltration rates and reducing erosion and runoff

3) Improves the moisture holding capacity of light soils – reducing water loss and nutrient leaching, and improving moisture retention

4) Improves the cation exchange capacity (CEC) of soils

5) Supplies organic matter

6) Aids the proliferation of healthy soil microbes

7) Supplies beneficial microorganisms to soils and growing media

8) Encourages vigorous root growth

9) Allows plants to more effectively utilize nutrients, while reducing nutrient loss by leaching

10) Enables soils to retain nutrients longer

11) Contains humus – assisting in soil aggregation and making nutrients more available for plant uptake

12) Buffers soil pH


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2. Potential Benefits of Composting WWTP Solids on Guam

Guam’s unique attributes make the prospective benefits of a biosolids composting project especially compelling. High tipping fees and limited land space incentivize increased recycling to maximize landfill space. The estimated hauling and disposal cost, based on the May 2017 NDWWTP Facility Plan of $185/ton, is 366 percent higher than the average tip fee of $50.60 in the United States (Rosengren, 2017). GWA will realize significant cost savings if the biosolids are diverted to a lower cost option such as composting.

2.1 Increased Rate of Recycling and Extension of Landfill Life

All dewatered sludge/biosolids from NDWWTP are currently landfilled, with an estimated life of 2065 for the current and adjacent landfill facility to accept the maximum month sludge production. Diverting biosolids to composting will extend the life of the landfill, which is paramount for Guam because of the limited space to expand and high cost of disposal. Landfill capacity is a continued concern. In a 2014 Biocycle interview, Mark Calvo, director of military buildup for the Governor of Guam, explained: “Capacity is one objective of the Zero Waste Plan, because it costs $10 million to $15 million to open a new landfill cell…” (Johnston, 2014).

Reuse of Guam biosolids through composting will help Guam meet its recycling goals as described in the Zero Waste Plan, which calls for an increase from 18 percent diversion from landfills to 37 percent in 2030 (Government of Guam, 2013). The increased diversion may also provide new DoD facilities a means to claim green credits for beneficial reuse of organics.

2.2 Sustainable Method of Solids Management

Composting biosolids is preferable over landfilling, because it is a beneficial reuse of the material. The composting process allows the nutrients in biosolids, such as phosphorus, potassium, and nitrogen, as well as organic carbon, to be recycled rather than disposed of. The USEPA has encouraged the reuse of biosolids since 1984 with formal policy statements and has worked since then to actively promote biosolids management practices that include reuse and recycling over disposal (USEPA, 2018).

2.3 Ability to Co-Compost Multiple Waste Streams

Co-composting of biosolids and other waste streams has been successfully practiced throughout North America. Biosolids must be composted with a bulking agent such as woodchips or use other materials such as green waste. Co-composting has also been used with other waste material streams, such as clean wood wastes, agricultural wastes, soiled paper, and shredded tires.

One example of successful co-composting is the Public Utilities and Public Works departments in Hillsborough County, Florida, which worked together in 2016 to pilot and ultimately construct a co-composting operation (Figure 3). The project accepts 29,000 tons per year of biosolids and green waste and creates a beneficial product that is used as a soil amendment by local farmers.

The volumetric ratio of green waste (ground to 6-inch minus) to biosolids (dewatered to about 15 percent solids) is 3:1 and uses a modified static aerobic pile methodology. The new co-composting operation is expected to save the Public Utilities Department approximately $1.5 million per year in disposal and transportation costs of biosolids (Clark, 2016).

Figure 3. Hillsborough, Florida Composting Pilot



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2.4 Production of Valuable Soil Amendment Product

Biosolids compost has a wide range of uses as a soil amendment or fertilizer in the horticulture, landscaping and agricultural markets (Figure 4). Compost has the unique ability to improve the properties of soils and growing media physically, chemically, and biologically. Compost is especially beneficial when added to soils with extreme or marginal conditions of low organic content, very high sand content, or very high clay content to make them more beneficial for plant growth and sustenance. Because of these unique characteristics, composts have been widely used for landscaping in public and private settings alike.

Figure 4. Typical Biosolids Compost Use for Roadside Construction Revegetation After application on the left and 5 weeks after seeding on the right.

On Guam, landscaping is believed to be a significant market due to ongoing development of residential, commercial, and public space development activities. Biosolids compost can provide a sustainable on-island produced fertilizer product for local farmers, which could stimulate interest in the growing of locally sourced food crops adding to local food supply/security. Compost could possibly be used to remediate the closed Ordot Dump by applying it as a final cover to function as a biofilter to remove releases of fugitive volatile organic compounds, odors, and methane that may be escaping the existing biogas collection system and the final cover there. Use as an alternate daily cover (ADC) at the Layon Landfill is also a potential use of the product; the USEPA has published information regarding that potential use

(USEPA, 1997).

2.5 Cost Savings vs. Planned Future Class A Exceptional Quality Processes

As discussed in Section 1.2, Phase I solids management improvements at the GWA NDWWTP are being designed and are planned to be built within the next 4 to 6 years at a capital cost of $13.2 million, to manage the increasing solids production. The current plan is to continue landfilling the expected annual production of 14,200 tons of dewatered solids at an annual cost for hauling and landfilling of approximately $2.6 million in 2025, based on current landfill rates. There is a Phase II expansion option that would add autothermal aerobic digestion, which would reduce the amount of WWTP solids being landfilled, but at an additional capital cost of $27 million over the cost of Phase I improvements. The annual cost of hauling and landfilling the 6,800 tons of dewatered solids in that scenario would be $1.25 million based on current landfill rates. If the entire quantity of sludge cake material were to be composted, the capital and O&M cost savings over Phase II planned improvements could be significant. Further, the compost produced could be marketed and used as a soil amendment product with multiple landscaping and horticulture outlets. Biosolids compost could also be used as part of the daily and final landfill cover material, further adding to overall waste management O&M cost savings on the island.


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2.6 Expandability and Flexibility of Process

Composting of biosolids is a wonderfully flexible process. As discussed in Section 2.3, there are a wide variety of biosolids composting technology options available, most all of which are readily expandable. Many communities develop pilot programs to test the concept first and then from there develop full-scale systems. Pilot programs are low-cost and simple to initiate. The benefits of developing a pilot study for many communities such as communities on the island of Guam include the following:

• Demonstrate the process to operators, regulators, and the public using local sources of sludge and bulking agents

• Demonstrate that suitable process control and odor control can be provided in a wet coastal climate

• Collect operating data to use in properly sizing and designing full-scale systems

• Collect data on O&M costs

• Generate compost products for testing and use in local product market surveys

An example pilot study in a wet coastal environment is shown in Figure 5.

Figure 5. Kodiak, Alaska, Aerated Static Pile Compost Pilot with Odor Control

With the quantity of biosolids being produced at the NDWWTP on the island of Guam increasing, a possible approach to investigate composting would be to perform a similar pilot study and determine costs and a strategy for developing a full-scale system to manage a portion of or all the expected sludge production. By starting small and expanding, operations staff can learn the process and begin market development for the product over time. This approach of starting small, gaining success, and then expanding the full-scale system has proven successful for dozens of utilities who have established biosolids compost programs throughout North America.

2.7 Ownership and Operating Strategies/Options

Many of the biosolids composting facilities initially built in the U.S. were developed by municipalities through traditional infrastructure delivery processes (i.e., design-bid-build or DBB). However, in the past couple decades, the landscape of municipal infrastructure projects in general, has changed. Part of the upsurge in popularity for alternative delivery methods is a result of increasing capital funding pressures placed on municipalities. In many jurisdictions, funding of new biosolids management facilities must compete not only with other new developments, such as water treatment plants and recreation facilities, but also with the capital requirements to upgrade or replace aging infrastructure. Each of the traditional and alternative project delivery methods has its own attributes that generally differ in terms of allocation of



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risks and responsibilities, scheduling and schedule certainty, ownership, performance guarantees, and procurement complexity. The common models for procuring waste composting/processing facilities are shared with other infrastructure development models, and include the following:

• Conventional DBB • Alternative delivery • Public-private partnership (P3)

Increasingly, in the organics industry, alternative delivery projects often follow a design-build-operate (DBO) model. However, alternative delivery options encompass a much wider range of delivery methods that can also involve ownership and financing options.

On the island of Guam, part of the strategy for developing a composting facility must encompass location. Table 3 shows how some of the structures discussed above could be applied to this project.

Table 3. Potential Ownership and Operating Structures

Location Structure Benefits

Adjacent to WWTP Wastewater utility owns and operates Operations staff can be shared

Permitting costs reduced

Utility costs minimized

Adjacent to WWTP Owned by wastewater utility, operated by 3rd party 3rd party can market compost product

Offsite, Landfill P3, DBO Diversion of other waste materials as bulking agent

If ownership and operating responsibility for the process is to be that of the wastewater utility, locating the composting operation adjacent to the WWTP makes the most sense. In this way, operations staff can be shared between the WWTP and the composting facility, permitting costs reduced, and utility costs such as water, electricity and wastewater services minimized. A nuance of this approach could be ownership by the utility but operation by a third-party contractor who would be responsible not only for operating the composting facility but also for marketing of the compost product. P3 partnerships with a contractor to DBO an offsite composting facility are also possible and generally successful if an appropriate offsite location can be secured.

3. Potential Considerations and Challenges

3.1 Chosen Technology, Facility Siting, and Good Neighbor Issues

Compost technology process selection must consider multiple variables simultaneously to achieve the desired objectives. In virtually every case, key objectives are to eliminate disease causing organisms in the biosolids, reduce biosolids odors, and produce a marketable product. The technology chosen to perform these objectives will be influenced by the following:

• Site size and constraints • The proximity of neighbors • Local weather conditions • Bulking agent availability • Degree of process controls desired • Capital and operating cost impacts

Land requirements, site characteristics, and proximity to neighbors must be addressed early in the planning and design process to determine suitability of the compost process type, the ability of the selected process to fit onto the available land parcel, and the level of odor control needed.


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3.1.1 Process Considerations

Because of Guam’s prolific precipitation (over 90 inches annual on average), a covered active composting process will be required, at a minimum. To prevent destruction during typhoon season, the composting must either take place inside a concrete building or be performed outside of the months when this is a risk. This will also minimize contaminated water management and costs. With these process considerations, development of composting facilities today can be done to ensure the operations are good neighbors with no detrimental odor impact. In addition, considerations for the chosen technology should include the following:

• Proximity to the point of generation of the solids • Point of generation of collected bulking material (such as yard wastes) • Availability of suitable roads • Availability of utilities such as power, water, and wastewater collection

3.1.2 Ability of Process to Operate in a Wet Climate

In tropical marine climates, adequate drainage and aeration become paramount for healthy composting operations. Receiving and mixing operations can be designed indoors or under cover (Figure 6). The active composting process may include negative or positive air flow to provide aeration to manage pile temperatures and to capture and treat process odors. Commercial composting is already practiced on Guam, as well as in other locations with similar climates such as Kodiak, Alaska; Honolulu, Hawaii; and throughout Florida.

Figure 6. Enclosed Mixing and Covered Biosolids Composting Operation, Kodiak, Alaska

3.1.3 Ability of Process to Control Odors

Because the wet climate dictates that the receiving and mixing operations will be covered or located indoors, most of the odorous emissions will already be captured. Negative or positive (aerated static pile) ASP will also likely be implemented to provide proper aeration, which will manage odors in tandem by driving them through a biofilter before air is released outside. If neighbors are located within 1 mile of small facilities (less than 10 wet tons per day) or within 3 miles of larger facilities, then odor modeling is recommended to determine the level of odor controls needed for the planned technology. Comparison of



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the odor effects of various compost technology choices or odor containment and treatment choices can and should be done to effectively engineer the level of controls needed.

3.1.4 Truck Traffic Issues

Currently, 13 roll-off containers of biosolids are hauled from the NDWWTP to the Layon Landfill weekly; the facilities are located on opposite ends of the island, approximately 25 miles by car. Future truck traffic will be dependent on the site selected for biosolids composting, if built (Table 4).

Table 4. Potential Truck Traffic by Project Location

Location Truck Traffic for Material Processing Truck Traffic for Product Shipment

Adjacent to WWTP Additional hauling of bulking agent to the site.

Roughly the same volume of compost to leave the site as the amount of dewatered solids produced.

Adjacent to Layon Landfill Same volume and distance haul for solids

Minimal because all solid waste is hauled here already. Same vehicle transport of compost out of the site.

If the composting facility is sited at the NDWWTP, the truck traffic from the WWTP to the Layon Landfill will be eliminated. Instead, hauling of bulking agent to the WWTP will be needed and transport of compost to markets will be added. If the biosolids composting is sited at the landfill, then truck traffic to the landfill should remain relatively the same as current operations, apart from added bulking agent if needed and transport of compost out to markets.

3.2 Capital Cost of Appropriate Compost Facility

Compost facility technologies are highly variable, as discussed in Section 1.3. The appropriate composting technology selection is critical for a land-locked island setting such as Guam. Odor control of the process and proper process protection and management of rainwater in the wet environment are crucial to the success of a biosolids composting program. Simple open operations on unimproved soil surfaces are simply not sufficient in this island environment subject to periodic typhoons, and should be avoided. Therefore, the infrastructure for an appropriate composting technology for Guam will most likely need to include paved or concrete surfaces, roofs/buildings to cover the feedstock receiving, mixing and active composting stages, and collection and treatment of process off gases through biofiltration systems to adequately control odors.

3.2.1 Example Facility Costs

Based on the predicted quantity of biosolids cake that will be produced from the upgraded WWTP, if all the cake were to be composted, the facility will need to manage 40 to 50 wet tons per day of dewatered cake material. This is a relatively small- to medium-sized operation and should be able to be constructed for significantly less capital cost than the currently planned Phase II improvements of autothermal aerobic digestion, which has a price tag of over $27 million. For comparison, a compost facility built in Virginia in 2010 has twice the capacity of what is needed for Guam and had a construction cost of slightly less than $14 million. Even with inflation and the higher cost of construction materials in Guam, a compost facility of the appropriate size and technology needed could be built for significantly less than $27 million. Additional analysis is needed to confirm capital and operating costs for a biosolids composting facility on Guam.

3.2.2 Phased Approach

Another option is to size the composting facility to manage the projected increase in sludge production only (approximately 16 to 20 tons per day capacity), with the option to expand later as operating experience is gained. This option would allow continued landfilling of the current level of cake production in the near term without immediate impact to the fiscal needs of the landfill. Kodiak, Alaska, was able to build a 10-ton-per-day facility in a similar wet environment for less than $5 million just 3 years ago

(Williams et al., 2018).


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3.3 Ability to Identify and Secure Appropriate Bulking Agent Materials

3.3.1 Current Green Waste Operations

According to the 2006 Guam integrated Solid Waste Management Plan, up to 40 percent of the waste accepted at the Ordot Dump was yard trimmings. Currently, residents can bring their green waste to several locations on the island, including Northern Hardfill in Yigo, Pacific Topsoils and Compost in Ordot, and Mahita Farms. The price for acceptance at these facilities ranges from $13.50 to $25 per truck bed. The Guam Fire Department also allows the open burning of green waste with a permit, which can be obtained at various fire stations. Potential diversion to a composting operation could reduce air pollution associated with open burning and potentially incentivize capture of these potential bulking materials with lower tip fees for clean loads of woody material suitable for composting.

3.3.2 Required Quantity

Significant quantities of green or wood waste would be needed to compost all the biosolids produced. Taking the 2025 estimate of 14,200 tons of biosolids from Section 1.2, a minimum of 6,000 to 8,000 tons of bulking material would be needed (annually), depending on the characteristics of the bulking agent materials available. Normally, during the early stage of compost facility planning, an assessment of available bulking materials is recommended. This could be performed as a part of a pilot study, as suggested in Section 3.2.

3.4 Fiscal Impact on Landfill Operation

3.4.1 Economic Analysis for Tip Fee

A conservative assumption would be that the revenue may not decrease at the landfill. This will require the tip fee to increase from $172/ton to $187.75/ton.

Approximate Current Revenues = Annual Tons Disposed x Tip Fee

95,000 tons x $172/ton = $16,302,000 revenue/year

Reduced Annual Tons = 2017 Total Tons – 2017 Biosolids Tons

95,000 tons – 8,170 tons = 86,830 tons

New Tip Fee Required to Keep Same Revenue = Current Revenues / Reduced Annual Tons

$16,302,000 / 86,830 = $187.75/ton

3.4.2 Consideration for Evaluating Fiscal Impact on Landfill

The following considerations should be used to assess the fiscal impact on the current Layon Landfill operation if the sludge were diverted to composting:

• Consider operational cost savings from diverting up to 9,000 tons from the landfill. Operational effort should decrease and yield savings, which may offset the revenue loss. Additional analysis is needed to evaluate this.

• Consider the percentage of the overall waste accepted at the landfill that is comprised of the biosolids:

– According to the data in the Guam Solid Waste Association August 2017 Quarterly Report (Gershman, 2017), the biosolids make up approximately 9 percent of the overall waste tonnage accepted at the landfill.



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• Consider only using new tonnage originating from upgrades and growth for composting and not divert any existing tonnage from the landfill:

– As discussed in Section 1.2, the projected average annual sludge quantity that will be produced once the Phase I planned WWTP upgrades are completed is estimated to be 14,200 tons in 2025. This quantity represents a 75 percent increase in sludge cake production or an additional 6,000 tons annually that is planned to be landfilled beginning in 2025 or sooner. These additional tons could be diverted gradually, as they are realized, to a biosolids composting project, so the landfill never experiences a decrease in tip fee revenue. As experience is gained in operating the full-scale compost facility, the economics can be better understood, and an analysis can be performed on the effects if all the sludge were diverted to compost.

• Consider composting the sludge at the landfill site and collect the same tip fee:

– If composting is sited at the landfill, then the landfill could still collect the tipping fee. If the cost to compost is less than the current disposal, then the landfill operator could increase revenue from diverting this waste stream by sharing savings with GWA, thus incentivizing the operator to divert more sludge to composting.

At a high-level assessment, multiple options allow for the fiscal health of the landfill to remain unchanged or even benefit from composting the sludge material.

3.5 Product Marketing

Biosolids sales throughout the U.S. have been simplified by the USEPA’s 40 CFR Part 503 regulations, which provide a singular standard for biosolids quality with very few exceptions. These regulations control the acceptable levels of pathogens and metals in land-applied biosolids (Archer, 2007).

3.5.1 Product Considerations

The product created by composting the biosolids will be a Class A biosolids, meaning undetectable pathogen and very low metal levels, that can be marketed as a fertilizer product. Guam has the challenge of not having an established biosolids market or a history of public acceptance. Marketing will be required to educate consumers on Class A biosolids compost and its uses and overcome concerns about its origin. Sales into the commercial sector, including landscaping and agriculture, are typical paths for product sales. One of the first steps in development of an effective biosolids compost marketing program is to perform research at the nearest land grant university, in this case the University of Guam, to test the use of biosolids compost that is produced using locally sourced plantings and practices. In this way, buy-in from local horticulture, landscaping, and agronomy experts on the island will be strengthened and concerns adequately addressed.

3.5.2 Product Quality and Value

The value of compost from biosolids feedstocks is well established in professional markets at varying prices that are dependent upon the local market and blend achieved. Uses primarily include roadside and landscaping applications for facilities that include parks, golf courses and athletic fields. Biocycle’s 2010 Biosolids Composting Update reported that the price range for biosolids composting products reported by facilities in the United States was from $6 to more than $30 per cubic yard (Goldstein, 2010). Williams, Datta, and Alexander reported the average price of biosolids compost to be $10.21 per cubic yard with very strong markets, based on a survey of 25 operating facilities in 2012 (Williams et al., 2012). Pacific Topsoils and Compost, Guam’s largest supplier of topsoils and compost, sells their compost products for $19 to $26 per cubic yard depending on screening and composition (Pacific Topsoils and Compost, 2019). Analysis of a biosolids compost product will be required to confirm compliance with 40 CFR 503 regulations.


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3.6 Public Outreach

3.6.1 Anticipating Public Concerns

Public concern over a new biosolids composting should be anticipated and planned for. A comprehensive public outreach plan will help the public feel that composting of sludge and the use of composted biosolids is safe and sustainable.

While there is substantial scientific evidence that proper biosolids management does not pose a substantial risk to the environment or public health, the public can still be skeptical. Research has shown that public acceptance increases when the following are true (Cubed, 2009):

• The degree of human contact is minimal. • Protection of public health is clear. • Protection of the environment is a benefit of reuse. • Promotion of resource sustainability is a benefit of reuse. • The community has high awareness of waste management issues. • The perception of the quality of the biosolids products is high. • Confidence in local management of public utilities and technologies is high.

3.6.2 Public Education Regarding Product Use

The Class A biosolids that would be produced through composting are considered a fertilizer/soil conditioner by the USEPA rather than a sludge. A program will be required to educate potential users on the value and the proper uses of a biosolids compost product. Historically, the first few years of a biosolids compost program require significant effort to test and demonstrate the value of compost. However, once a program is established and users see first-hand the benefit of the product, a reduced level of monitoring and marketing is generally required.

4. Recommended Next Steps

The recommended next steps include a pilot and outreach study to investigate the following:

• Demonstrate the ability of the process to produce Class A EQ compost compliant with all USEPA CFR Part 503 standards

• Allow all stakeholders to observe the process with Guam-specific solids

• Determine bulking agent availability and cost

• Confirm the quality (metals content) of the sludge and compost produced

• Engage the University of Guam to perform growth trials comparing compost use to conventional horticulture and landscaping practices

• Perform end user market survey for compost product(s) generated

• Analyze potential cost savings for use as landfill cover to supplement or replace the material currently used

• Begin developing a product marketing plan

• Consider potential site locations for a full-scale composting system

• Evaluate potential owner and operator arrangements

• Use data from the pilot study, sizing analysis, and facility construction and operations cost estimates for further economic analysis to confirm financial sustainability



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5. References Archer, M. 2007. Marketing Biosolids: The Experience of Milorganite with Special Reference to Canada. Milwaukee Metropolitan Sewerage District (MMSD). January.

CH2M HILL (CH2M). 2018. Pre-Design Solids Process Alternative Analysis. Technical Memorandum 7. April 19.

Clark, B.S. 2016. “County Departments Reduce Cost with Cocomposting.” BioCycle March/April 2016, Vol. 57, No. 3, p. 60. https://www.biocycle.net/2016/03/17/county-departments-reduce-costs-with-cocomposting/.

Cubed, M. 2009. Bay Area Biosolids management: Challenges, opportunities, and policies. September. https://www.cityofpaloalto.org/civicax/filebank/documents/23066/.

Environment Canada. 2013. Technical Document on Municipal Solid Waste Organics Processing.

Epstein, E. 1997. The Science of Composting. New York: CRC Press.

Gershman, Brickner & Bratton, Inc. (Gershman). 2017. Quarterly Report of the Receiver. August 23. https://www.guamsolidwastereceiver.org/pdf/Tab1-Quarterly-Report-of-the-Receiver-8-23-17-Final.pdf.

Goldstein, N.B. 2010. “Biosolids Composting in the United States – 2010 Update.” BioCycle December 2010, Vol. 51, No. 12, p. 35.

Government of Guam. 2013. Reaching for Zero: A Blueprint for Zero Waste in Guam. “Volume 1: Guam Zero Waste Plan.” http://one.guam.gov/images/documents/Guam_ZW_Final_Volume%20I_r1_2013%2007%2015%20JG.pdf.

Guam Environmental Protection Agency. 2006. Guam 2006 Integrated Solid Waste Management Plan. September.

Guam Waterworks Authority (GWA). 2017. Northern District WWTP Facility Plan Report. May.

Johnston, M. W. (2014). “Guam Advances Zero Waste Plan.” BioCycle February 2014, Vol. 55, No. 3, p. 36. https://www.biocycle.net/2014/02/21/guam-advances-zero-waste-plan/.

Pacific Topsoils and Compost. 2019. Compost. https://www.pacifictopsoilsguam.com/commercial/compost.

Rosengren, C. 2017. Average Landfill Tip Fees Up 3.5% So Far This Year. July 12. https://www.wastedive.com/news/report-average-landfill-tip-fees-up-35-so-far-this-year/446834/.

United States Composting Council. 2018. New Compost Definition – Results From USCC Work with AAPFCO. March 2. https://compostingcouncil.org/blog/news/new-compost-definition-results-from-uscc-work-with-aapfco/.

United States Environmental Protection Agency (USEPA). 1997. Innovative Uses of Compost Bioremediation and Pollution Prevention.

United States Environmental Protection Agency (USEPA). 2018. Biosolids Laws and Regulations. February 7. https://www.epa.gov/biosolids/biosolids-laws-and-regulations.

Water Environment Federation. 2012. Solids Process Design and Management. Alexandria, Virginia.

Williams, Todd, Tania Datta, and Ron Alexander. 2012. “Biosolids Compost - What's it Worth?” 26th WEF Residuals and Biosolids Conference. Raleigh.

Williams, Todd, Bud Alto, Floyd Damron, Mark Kozak, and Lori Aldrich. 2018. “Composing a composting solution in the Last Frontier.” WE&T Magazine. September.

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