You are here:
A STUDY OF LAND APPLICATION OF ANAEROBICALLY DIGESTED BIOSOLIDS
Citation:
ACHESON, C. M., R. F. HERRMANN, E. Foote, S. Naber, R. C. BRENNER, T. DAHLING, M. Graves, J. HECKMAN, T. STROCK, S. J. STOLL, J. Tompkins, S. VonderHaar, S. WRIGHT, AND L. ZINTEK. A STUDY OF LAND APPLICATION OF ANAEROBICALLY DIGESTED BIOSOLIDS. Presented at 10th Annual National Biosolids Conference/Workshop, Potomac, MD, June 16, 2008.
Impact/Purpose:
To evaluate land application of anaerobically digested biosolids at agronomic levels at a field-study research project that was conducted in 2004-2005.
Description:
A field-scale research project was conducted in 2004-2005 to evaluate land application of anaerobically digested biosolids at agronomic levels. Biosolids had not been applied to this land previously. For this study, biosolids wee applied in a 100-m diameter circle by a side discharge manure spreader. The soil sampling portion of this study focused on biosolids distribution, microbial community characterization, fecal coliform concentrations, and the concentration of alkyl phenol ethoxylates (APEs) and their degradation products. Soil samples were collected from 3 replicate plots within the application area prior to biosolids application (2 sample events) and for 4 months following application (7 sample events). Biosolids distribution for each replicate plot was determined by measuring the dry mass and volatile solids of applied material at more than 15 locations in each plot. Fecal coliforms were measured as indicators of pathogenic bacteria. Phospholipid fatty acids (PFLA) were measured to characterize the size and diversity of the microbial community. APEs, including degradation products such as octylphenol (OP) and nonylphenol (NP), were measured. APEs concentrations and PLFA was measured at three soil depths. At each sample event, three replicate samples were taken from each replicate plot for fecal coliforms, PFLA, and APEs. Soil toxicity was screened using the 14-day earthworm mortality and 5-day seed germination and root elongation in lettuce and oats bioassays. Soil samples were screened for toxicity prior to, immediately after, and 4 months after biosolids application. In addition, supporting information such as soil agronomic characterization, temperature, and weather data were gathered. Analysis of variance (ANOVA) was used to compare dry mass and volatile solids data from biosolids distribution samples. Fecal coliforms and APEs were analyzed by ANOVA as a function of replicate plot, time, and depth (for APEs). Principal component and hierarchical cluster analysis were used to analyze PLFA data as a function of replicate plot, time, and depth. Statistical analysis of this data is ongoing; however, some preliminary conclusions are apparent. The data displayed significant variation which complicates data interpretation. This variability may be a function of many experimental factors including: biosolids application equipment, physical properties of the biosolids, sample numbers, sample size, sampling equipment, and homogenization techniques. Fecal coliform concentrations increased following application. The microbial community based on PLFA returns to pre-application structure within 30 days of application. NP and OP were observed in the surficial samples after biosolids application. APEs and degradation products were not found in deeper samples. Soil toxicity screening assays showed no consistent effect of biosolids application. Based on this initial study, more detailed studies are planned to reduce: data variability, uncertainties in the rates of fecal coliform survival, and NP and OP removal rates. In addition, more sensitive soil toxicity assays will be adapted from the literature.