Suitability of Penn State’s Biosolids for Land-Based Recycling: A Greenhouse Evaluation
Open Access
- Author:
- Clees, William
- Graduate Program:
- Biorenewable Systems
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 18, 2019
- Committee Members:
- Herschel Adams Elliott, Thesis Advisor/Co-Advisor
Heather Elise Preisendanz, Committee Member
Richard Charles Stehouwer, Committee Member
Paul Heinz Heinemann, Program Head/Chair - Keywords:
- Biosolids
Land application
sustainability
Copper
Phosphorus
Wastewater - Abstract:
- Land application of biosolids recycles nutrients and organic matter that beneficially impact agronomic crops. The Pennsylvania State University’s biosolids, however, are not currently managed for sustainable nutrient reuse and recovery. Current literature provides sufficient information regarding both the benefits and challenges of biosolids application. The research aimed to assess the feasibility of recycling the University’s biosolids by land application for crop production. First, biosolids from the University’s wastewater treatment plant were assessed for regulated use in land application. The second phase involved a greenhouse evaluation using three treatments: soil only (control), dairy manure-amended soil, and University biosolids-amended soil. The manure and biosolids were applied to provide 168 kg of plant-available nitrogen (PAN) ha-1. Perennial ryegrass (Lolium perenne) was established and periodically harvested. Harvest yields were measured and ryegrass tissue was analyzed to determine nutrient and trace element concentrations. Biosolids and dairy manure analysis indicated both materials contained typical amounts of nutrients and most trace elements. However, the biosolids Cu concentration (1073 mg kg-1) was high compared to the national average (500-600 mg kg-1), likely due to backwash of steam condensate that contacted copper pipes in heat exchangers prior to being discharged to the wastewater treatment plant. Because Cu is regulated in land application of biosolids due to its phytotoxic potential, this element was considered particularly important in evaluating the suitability of land-based recycling of the University’s biosolids. Biosolids and manure treatment tissue weights were higher that the controls in the first harvest. This was likely due to the addition of N and possibly P in the soil amendments. Cu levels in biosolids and manure tissue samples (~15 mg kg-1 dry weight) were statistically higher than in controls (12.4 mg kg-1) but below levels reported in the literature (21-30 mg kg-1) at which phytotoxicity begins to occur for ryegrass. Second harvest wet tissue yields were similar between all treatments. Manure amended dry weight yields were statistically different from control yields. However, biosolids treatment yields were not statistically different from manure or control treatment tissue yields. The level of ryegrass tissue Cu in the biosolids treatment (14.5 mg kg-1) was statistically higher than for the manure treatment (12.2 mg kg-1). An unexpected finding was that manure and biosolids additions resulted in statistically lower Al and Fe concentration in the ryegrass tissue compared to the controls in both harvests. This is possibly due to the reduced plant uptake of these elements when complexed by organic matter added via the amendments, or from the “dilution effect” whereby rapid plant growth stimulated by addition of a deficient nutrient (e.g., N) results in lower (diluted) tissue concentrations of other elements. Limited inferences can be drawn from the root analysis conducted at the end of the experiment because the small mass of roots collected was sufficient for only a single sample per treatment. However, the roots from the biosolids treatments appeared to have much higher Cu than the controls or manure treatments. Incomplete removal of root-zone soil from the roots could not explain the results. Literature indicates that many plants, including ryegrass, are Cu “excluders”, meaning they uptake and retain Cu in their roots, but only translocate a small portion to aboveground tissue. Sustainability of trace element accumulation in soil from multiple applications was addressed through a mass balance approach. The results suggest that two elements (Cu and P) could limit biosolids applications. If the site lifetime was limited by the soil loading of Cu, then ~ 75 years of application could occur before soils reached the ceiling limits for Cu in PA soils of 1480 kg ha-1 (1320 lbs. ac-1). However, loading rates would be affected much sooner if the P-Index was mandated for biosolids application. Environmentally relevant P additions would limit biosolids spreading by the 4th year of application. Improving the N:P ratio for the University’s biosolids would be needed for a long-term land application program using agricultural land. Similar research with biosolids-amended soils have demonstrated favorable results for crop production and therefore advocates for reuse of the University’s biosolids to enhance soil fertility. However, changing the biosolids N:P ratio would be necessary for a sustainable agricultural land application program under evolving P management policies. Use of University’s biosolids for reclamation of abandoned mind lands should be investigated. The ultimate goal is to inform future decisions aimed at positioning Penn State as an institutional leader embodying environmental stewardship and sustainability in all activities.