BioCycle February 2006, Vol. 47, No. 2, p. 42
A central Pennsylvania facility has become the first in the United States to receive a permit to make and use biosolids from a process-controlled vermiculture system.
Larry Craig and Shaun Ankers
THE TOWNSHIP of Granville (pop. 4,895) – located in central Pennsylvania – has two wastewater treatment plants, 30 miles of sewers and seven pumping stations. As little as 20 years ago, Granville had no sewerage system at all, but now services two neighboring municipalities as well. Traditionally, the aerobically digested biosolids from the township were sent to the landfill for disposal. When it was announced in 2001 that the local landfill was closing, Granville looked for a solution that would enable the biosolids to be recycled for beneficial use.
A study was undertaken that considered a number of options (including trucking to a distant landfill) and decided, based on environmental, operational and overall cost benefits, to pursue a solution using large-scale vermiculture (earthworms). The solution was supplied by an Australian company, Vermitech, and utilizes earthworms housed in large, industrialized, continuous-flow reactors, to process and transform the township’s biosolids into an attractive, odor-free material known as vermicompost.
Commissioned in 2004, the facility today accepts all of Granville’s biosolids outputs and also that of two neighboring townships, approximately 70 dry tons per year. The facility was built with financial assistance from PennVest and PaDEP Growing Greener grant program. In February 2005, the facility was granted a General Permit for Exceptional Quality Biosolids by the Pennsylvania Department of Environmental Protection (PaDEP). The Vermitech System, as the technology is called, utilizes documented process control and operating parameters to ensure production of consistent end product, an important factor in ensuring compliance with the permit. Gran-Verm, as the Township’s end product is branded, has been well received by local vineyards, golf courses and sod suppliers. The township expects to sell all of its output this year; the facility has been in operation since September 2004 and the Gran-Verm product became available for purchase by the public in August 2005. The first complete 100 ton batch will be produced in the spring of 2006 and at the present time over 80 percent of the product is sold.
GRANVILLE’S WASTEWATER TREATMENT PLANT
The main facility, Junction WWTP, uses an ABJ Sequencing Batch Reactor (SBR) process and is permitted to treat 500,000 gallons per day of dry weather flow. The facility has one full-time operator. There are two 250,000-gallon SBR basins, two 250,000-gallon aerobic digesters, chlorine disinfection (about to be upgraded to UV), and an intermittent discharge to the Juniata River. Waste activated sludge is transferred and treated in aerobic digesters. Biosolids taken from the digesters are dewatered using a belt filter press to a cake of 12 to 15 percent solids. This cake, previously taken to landfill, is input to the Vermitech System.
This System (Figure 1) uses a semicontinuous flow reactor design with the following key features: Beds – The core of the technology is an open top, steel vessel or bed in which the earthworms are housed. There are four beds in the Granville facility, and each are 32 yds (29 m) long; Specialized materials handling equipment – A controlled blend of biosolids is fed to the surface of the bed on a regular basis (1-2 times per week). The earthworms consume the waste in and around the top region producing vermicompost. Preparing and feeding the biosolids in the correct mix and feed relationships is undertaken using the supplied procedures and equipment supplied. The vermicompost is harvested (removed) regularly from the base of the bed, using a cutting device. The bed then moves down, in plug-flow, creating space at the top for further feed. Harvested material is dried, screened and used (and sold) following a quality assured testing process.
EARTHWORMS STAY WITHIN THE BED
The earthworms stay in the bed permanently, although a small percentage of biomass (natural or process wastage) is removed during harvesting operations. There are several thousand pounds of earthworms in the system. The earthworm species, Eisenia (also sometimes called Tiger worms and Redworms), is a robust and productive species, well established in North America. The Granville inoculation stock was grown locally but there is no requirement to regularly restock the beds since the earthworms maintain their own population.
The process has much in common with a typical wastewater activated sludge, with the earthworm population balanced to the incoming food. The population will increase up to the point of food and space constraints. As with the wastewater plant, Granville operators are trained to monitor critical parameters and ensure the system is operated correctly and that feed rates are matched to population and other environmental parameters.
Use of moving parts and equipment is intermittent, mainly for routine tasks (feeding, harvesting, monitoring, etc). Outside of this, the system is designed to be unattended, with the earthworms continuously processing the biosolids. The Granville facility uses approximately 16 man-hours per week for all tasks including record keeping.
The process is designed to treat an average of 10 wet tons per week of biosolids from the aerobic digester at the Junction Treatment Plan. Dewatered biosolids are inspected before feeding and tested regularly for characterization purposes and to monitor long term trends. Test results are entered into a custom-made data base.
FEEDING AND MIXING
The feeder system provides the opportunity for biosolids to be mixed with a small amount of wood chips (supplied by the road crew and another opportunity for waste diversion). The wood chips are added as a structural agent rather than a composting or diluting agent. The exact feed rate is dependent upon a number of process control conditions including bed temperature, and population density, all of which are monitored via regular operator checklists.
The Granville facility uses a semiautomatic machine in which the feed is “cut” to the required depth and delivered onto a belt, which is pulled by a multipurpose winch at the other end of the bed. All operations are maintained with a hand controller. Speed and other parameters are adjustable to ensure an even depth and consistency and to ensure the feed is evenly dispersed. The process control requirements for these activities are contained in comprehensive Operations and Maintenance procedures and the supplier provided plant operators with proper training. As the new feed source is established, the beds are monitored for parameters such as worm population and distribution, moisture content, bed temperature, etc. These data are used to monitor and maintain the system within the normal operating conditions and to determine whether adjustments to additional process control measures (e.g. feed rate and frequency) are required. Regular audits (both qualitative and quantitative) of worm population and health are also undertaken.
The beds act as a plug-flow type unit and the exceptional quality (EQ) processes ensure that sufficient retention time is allowed for the required product quality. Typical retention time is several weeks.
The bed-bases have a special design that supports the bed material while also allowing access for a specialized harvesting/cutting device. The harvester is launched onto travel rails situated beneath the bed and powered using the winching system at the opposite end. The operator controls the depth and speed of cut.
Once harvested, the material falls onto a collection belt. The belt system is regularly extracted from one end of the bed and discharges into a trailer and removed for storage.
STORAGE AND HANDLING
After harvesting, the material is still moist but has been noticeably processed to a stable, humus-type material. The material is stored on-site during winter and, prior to the agricultural growing season, it is dried on an adjoining pad. Once it reaches the required moisture content it is screened to meet end product customer specifications (typically around 1/4 inch). The Township has elected to purchase its own screening machine (with a view to using at an intended future regional operation).
The end product is placed into a state of “quarantine” and is tested regularly for microbiological quality. Materials that are passed as suitable are identified with a batch number. The EQ system forbids material to be released without a batch number.
The quality control system adopted by the Township is based on the principles of HACCP (Hazard Analysis Critical Control Point), which includes identifying potential hazards, and adopting preventive measures to stop them occurring.
The EQ system is preventative, moving from reactive quality control to proactive quality assurance and targets resources at the most critical parts of a process. These features mean that the Township anticipates that the system can form the basis for, and be easily incorporated into, any future Biosolids Environmental Management System (EMS) that may be introduced as part of a regionalized facility.
PERMITTING AND PATHOGEN REDUCTION
The Granville facility was granted a General Permit for Beneficial Use of Exceptional Quality Biosolids by the Pennsylvania Department of Environmental Protection (PaDEP) after an assessment of compliance with DEP regulation in regards to numerous elements including biosolids quality, sampling and analysis, storage, distribution and record-keeping. These regulations are designed to ensure the safety and quality of the end product. Personnel from PaDEP, Granville and Vermitech, worked together to ensure that all elements of the program were complied with. Given that this is the first facility of its kind in the U.S.A., this represents a valuable benchmark for regulatory compliance of innovative technology applications. Specific requirements with regard to demonstrating the Exceptional Quality (EQ) of the end product were pathogen reduction, pollutant concentration and Vector Attraction Reduction (VAR).
The EQ biosolids end product must meet Class A pathogen standards (i.e., below detectable levels of viable Helminth ova, Enteric virus and Salmonella). The facility utilizes Alternative 4 (end product testing) for demonstration of this pathogen reduction. Under this regime, batches of end product were tested over a 60-day period to ensure they met the Class A standard. Ongoing testing will ensure continued quality of the end product.
The Vermitech System has been developed over a number of years into an industrialized system of process-controlled vermiculture that incorporates process, operating and quality parameters to achieve the standards of Class A. To further establish this innovative technology as a mainstream process, Vermitech is seeking to verify the process as a PFRP in accordance with USEPA 503 Regulations.
The pollutant levels of the end product were sampled and tested in accordance with a Sampling Plan complying with permit requirements. The pollutant levels in the end product conform to Table 3 levels and are consistent with the standards required for EQ biosolids.
To meet the standards of VAR, regular testing of volatile solids across the system demonstrates volatile solids reduction in excess of 38 percent. The Gran-Verm has shown itself to be a stable material capable of long-term storage.
To ensure the ongoing success of the facility – to produce the best quality end product and to ensure compliance with the facility permit, the Township has a structured support arrangement in place that mandates the following: Only trained and certified operators may operate the facility; It must be operated in accordance with operating manuals supplied by Vermitech; Regular records are kept and sent to the Vermitech technical team on a 3-month basis; Vermitech provides backup and technical support for a number of years; and Annually, technical staff from Vermitech will conduct an on-site audit of the facility and records.
The Township’s initial concerns were that, being based in Australia, the supplier would not be able to provide adequate support and spares. However, Vermitech is currently seeking to partner with U.S.A. firms to provide all the necessary services and equipment.
GRANTS AND FINANCING
The facility cost was in the order of $1.2 million. The Township has calculated that whole of life costs will make the solution much more attractive than the alternatives. The facility was assisted by grants from the Pa. DEP Growing Greener program, a state-based program designed to promote environmental initiatives and technologies for the environment and the State Infrastructure Investment Authority (PennVest).
Vermicompost is widely recognized as having beneficial properties for plant and soil health. Biosolids vermicompost produced from process controlled vermiculture contains not only nutrients but other beneficial qualities as well.
Research conducted in the U.S.A. and Australia by Vermitech and others have shown that a high quality vermicompost material has a significant positive impact on the biological status of the soil. Gran-Verm has been tested by Soil Foodweb laboratories and found to be rich in the necessary microbes and fungi, particularly for turf and grass applications.
Vermitech has provided the Township with technical assistance in the marketing of Gran-Verm utilizing the specific research and case studies to target applications in the local area. The Township has focused on vineyards, golf courses, tree farmers and sod growers as prime and likely customers of Gran-Verm. The Township has initiated local in-field trials and is in discussions with the local university to conduct further testing onGran-Verm.
Reception for the end-product has been strong. The Township has presold 80 tons of Gran-Verm for the upcoming 2006 growing season and interest continues to grow from local users. The Township has introduced smaller quantities for residential use in bag sizes ranging from 5 lbs. up to 50 lbs. and is presently receiving great interest.
With the establishment and success of this facility, the Township is contemplating the construction of a regional facility to take treated or partly treated sludges from neighboring towns, with the expectation that net costs for all could be reduced and provide a potential source of revenue from end product sales.
Larry E. Craig is the Sewer and Water Manager for Granville Township, Mifflin County, Pennsylvania. He can be contacted via e-mail at email@example.com. Shaun Ankers is the manager of Vermitech Ltd, based in Sydney, Australia who can be e-mailed at Shaun.firstname.lastname@example.org.
February 17, 2006 | General
Vermiculture Produces EQ Class A Biosolids At Wastewater Plant
BioCycle February 2006, Vol. 47, No. 2, p. 42