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Monitoring Alkyl Phenol Ethoxylates And Degradation Products After Land Application Of Anaerobically Digested Biosolids
Citation:
ACHESON, C. M., R. F. HERRMANN, L. ZINTEK, R. C. BRENNER, T. DAHLING, E. Foote, M. Graves-Allen, S. Naber, S. J. STOLL, T. STROCK, AND S. WRIGHT. Monitoring Alkyl Phenol Ethoxylates And Degradation Products After Land Application Of Anaerobically Digested Biosolids. Presented at SETAC North America 31st Annual Meeting, Portland, OR, November 07 - 11, 2010.
Impact/Purpose:
To evaluate land application of anaerobically digested biosolids at agronomic levels.
Description:
Annually, over 3 million dry tons of treated sewage sludge (or biosolids) are applied on agricultural lands in the U.S. In 2002, the National Research Council (NRC) recommended an examination of biosolids management practices including chemicals such as surfactants used in cleaning products and laundry detergents. Surfactants are produced and used in large volumes and one class, alkyl phenol ethoxylates (APEs), has been reported to disrupt endocrine activity by acting as weak estrogens. The NRC report expressed concern about the persistence of APEs in land applied biosolids noting that little field based data are available. A field-scale research project was conducted to evaluate land application of anaerobically digested biosolids at agronomic levels. One research objective was to characterize the APEs concentration and persistence in soil as a function of time and depth. Soil samples were collected from 3 replicate plots 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 ash mass of biosolids applied. In addition, phospholipid fatty acids (PLFA) were measured to characterize the size and diversity fo the microbial community in the sampled soil. APEs, including degradation products such as octylphenol (OP) and nonylphenol (NP), were also measured. Supporting information such as soil agronomic, temperature, and weather data were gathered. Total biomass based on PLFA varied from plot to plot, with depth, and with time for surficial samples. Total biomass concentration in shallow samples increased following application. Based on PLFA distribution, the microbial community shifted following biosolids application, but returned to pre-application structure within 28 days. NP and OP were observed in shallow soil samples for 98 days following application. Since these compounds are aerobically degradable in soil biosolids mixtures, the persistence of these chemicals may reflect exposure to anaerobic environments within biosolids particles or microbial preferences for other substrates in biosolids. At this site, land application of biosolids altered the biological and chemical characteristics of soil. In many cases, these changes persisted throughout the study. In the future, longer sampling periods and improved sampling procedures are recommended to refine these observations.