Sustainability practices are leading to the development and use of alternative products in the floriculture and wastewater industries, such as the use of biodegradable containers instead of plastic containers. The objective of this research was to evaluate the efficacy of using digested biosolids from a regional wastewater treatment plant as an ingredient in creating a biodegradable transplant biocontainer. The biosolids were tested for metals limits as specified by the U.S. EPA Part 503 Rule, and met the requirements for Class B. Multiple mixes of biosolids, fibers, starch, polymer, and natural glue were developed to provide overall pot stability and structural strength. Engineering tests, such as tensile strength, pH, and saturated paste tests, were conducted on the different mixes to determine the optimum strength that could be produced.
The top-performing biosolids mixes were used to make 10.2 cm (four-inch) pots that were compared in various ways to the market leaders, Peat Pots and standard plastic pots. A two-part mold was created on a 3D printer, which would allow for positive pressure to be used in forming the BioPots. Mixes were transferred to the lower half of the mold, the upper part was then plunged and fastened into the lower half, and then the mold with its mix was placed in an oven to dry. Laboratory germination bioassays were performed to test for the presence of phytotoxic compounds. Construction of BioPots for the lab-scale studies was tedious. Different methods (e.g., negative pressure systems) need to be investigated for use in producing the BioPots commercially.
Most of the BioPots survived the resiliency study. Leachate quality from the biocontainers was no worse than from the plastic containers. Some discoloration was observed on the biocontainers, but it was not due to algal/fungal growth. Growth of soybeans, marigolds, and romaine in the biocontainers was significantly better (e.g., increased height, leaf sizes, and weight) than in the plastic containers. / Master of Science / The Western Virginia Water Authority serves the City of Roanoke, and Counties of Roanoke, Franklin and Botetourt. Approximately 141 million liters per day (37 million gallons per day) of wastewater from the service area is treated at the Roanoke Regional Water Pollution Control Plant (RRWPCP). Solids are anaerobically digested and lagooned prior to agricultural land application; biogas is stored and used to generate electricity. After about nine months in the lagoon, 9.07 million dry kilograms (10,000 dry tons) of biosolids are land applied locally each year. Solids management costs are a significant part of the RRWPCP’s operating budget. In an effort to decrease costs and increase sustainability, there has been growing interest in resource recovery by producing a high-quality nutrient product that can be beneficially used. In January 2014, research to develop a high-quality biosolids product for beneficial use was initiated by Virginia Tech, in collaboration with the RRWPCP. The drivers, research goals, methodology, and results from that research will be presented.
The general public is familiar with several commercially available biocontainer products, such as Peat Pots and CowPots<sup>TM</sup>. They are used in nurseries, greenhouses, and households, and minimize plastic waste while also contributing organic material for healthy plant growth. The WPCP was intrigued with developing a biosolids product that could be marketed and used like the Peat Pots.
The objective of this research was to evaluate the efficacy of using digested biosolids from Roanoke WPCP as an ingredient in creating a biodegradable transplant pot. The biosolids were tested for and met the metals and contaminants limits as required by the U.S. EPA Part 503 Biosolids Rule. In addition to the biosolids, other fibrous materials, such as used cardboard or cellulose, were used to stabilize and add structural strength. Multiple blends, or mixes, were developed, each varying in biosolids and fiber content on a dry weight basis, as well as different additives such as starch, polymer, or a natural glue. Tensile and puncture tests were conducted on the different mixes to determine the optimum strength that could be produced.
The top performing mixes were used to create four-inch pots, for comparison to market leader, Peat Pots, and standard plastic pots. Greenhouse studies were conducted in two phases:
• Phase 1 – analysis of leachate and assessment of pot stability through watering cycles.
• Phase 2 - growth studies for soybeans, marigolds, and romaine. These plants were selected based on growth ability and/or sensitivity.
The RRWPCP does not currently produce Class A biosolids, but by producing biodegradable transplant pots, they hope to produce a high-value, sustainable product that meets Class A requirements and diversifies their current biosolids management program.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/75649 |
| Date | 08 March 2017 |
| Creators | Stone, Peyton Franklin |
| Contributors | Civil and Environmental Engineering, Boardman, Gregory D., He, Zhen, Daniels, W. Lee |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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