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Session- Degradation of Xenobiotics/Pesticides

 

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Degradation of Organic Contaminants in Sewage Sludge During Windrow Composting

 

Amundsen, Carl E. (1), Eggen, Trine (1), Hammer, Jan P. (2) and Lystad, Henrik (1)

 

(1) Jordforsk, Centre for Soil and Environmental Research, N-1432 Norway, (2) Lindum Regional Waste Company, N-3036 Drammen, Norway

 

In Norway, a major fraction of the sewage sludge is treated using anaerobic processes. For several organic contaminants present in sewage sludge aerobic treatment results in the most efficient degradation. Windrow composting, as a simple and often efficient aerobe treatment technology, may therefore be useful to reduce the content of organic contaminants in sewage sludge. This may increase the utilization potential of sewage sludge and reduce possible negative consequences when applied to soil. In this project sewage sludge from two primary wastewater treatment plants were mixed with spruce bark in the ratio 1:2 in large windrows (length 60m, width 5m, height 2m). The windrow was turned twice a week in 12 weeks. Temperature, O₂ and CO₂ were measured daily. Compost samples (triplicates) were taken from the windrow at start, and then after 1, 2, 3, 6, 12, and 28 weeks of composting. The content of polycyclic aromatic hydrocarbons (PAH), phthalate esters, 4-nonylphenol (NP) and nonylphenolethoxylates (NPEO), and linear alkyl benzene sulphonates (LAS), nutrients, total and water soluble organic carbon, as well as metals and parasites were determined in the compost samples. The degradation of SumPAH (16EPA), Di-(2-ethylhexyl)phtalate (DEHP), NPEO and LAS during the composting process was higher than 60%. The content of NP in the compost increased substantially during the composting process. The degradation of organic contaminants during the different phases of the composting process will be discussed and related to composting temperature and stability indicators like water soluble carbon.

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Persistent Herbicide Contamination of Compost at Or Below Practical Analytical Detection Levels

 

BEZDICEK, DAVID (1), Fauci, Mary (1), Caldwell, Dan (2) and Finch, Rick (2)

 

(1) Department of Crop and Soil Sciences, WSU. (2) Department of Animal Sciences, WSU, USA

 

Composting is an excellent method to recycle organic materials due to its sanitizing effect on weeds, disease organisms, and pesticides. Unfortunately, composts made from feed stocks treated with some persistent herbicides may retain phyotoxic levels injurious to plants. Clopyralid, detected in compost in the US and in some foreign countries, is extremely toxic to some legumes, tomatoes, potatoes and sunflower at levels of 10 parts per billion (ppb) or less.  Produced by Dow AgroSciences, clopyralid is a chlorinated pyridinecarboxylate that functions as a plant growth regulator. It is the active ingredient in over 30 products including Confront, Curtail and Stinger and is used to control annual and perennial weeds in crop production and in turf.  Typical symptoms include leaf cupping, loss of apical dominance, failure of trifoliate leaves to develop, and prevention of fruit set. Clopyralid-contaminated compost from grass clippings was noted in 1999 at nurseries in Spokane WA, in 2000 at Pennsylvania State University, and in 2001 at Washington State University from grass hay. Since, numerous instances of clopyralid contamination have been reported in compost in the US and in New Zealand. Because of the relatively high tolerance allowed for clopyralid, most laboratories do not routinely measure clopyralid below 50 ppb and injurious levels may not be detected. Studies are underway to further identify composting conditions and management options to enhance herbicide breakdown.   Recommendation/conclusions are: 1) Bioassay all feed stocks and compost for symptoms and verify with analytical tests; 2) become familiar with feedstocks sources and inquire whether persistence herbicides have been used; 3) re-examine the criteria when considering the registration and re-registration of persistent herbicides to include all possible end users of plant residuals; 4) re-examine the chemistry and formulation of existing and new herbicides for persistence in the environment so that the recycling and composting industries are not at risk.

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Herbicide Persistence in Finished Compost Products: A Case Study From Penn State.

 

BURKHART, ERIC P. (1), HOUCK, NADINE J. (2)

 

(1) Department of Horticulture, The Pennsylvania State University, (2) Department of Agricultural and Biological Engineering, The Pennsylvania State University, USA

 

Compost quality is perhaps the single most important factor to consider in the production and utilization of compost products.  Recent reports of herbicide persistence in finished materials have further supported this contention while creating a sense of frustration and concern among both producers and consumers. Research at the Pennsylvania State University is presently documenting contamination of finished compost products by the herbicide compound clopyralid.  The composts being studied are manufactured at the University using campus generated feedstock materials. Since the summer of 2000, these contaminated composts have been evaluated in order to(1) elucidate the pathway(s) of herbicide contamination; and (2) assess the impact of utilizing contaminated composts on a variety of vegetable crops under both greenhouse and field conditions. Results from the study have revealed differences in the response time and appearance of affected plants.  These findings are of practical significance to the compost industry, which is currently promoting the use of bioassays as a means of identifying contaminated products.   The study also serves to illustrate the complexities involved in identifying the source of contamination in products derived from mixed municipal and animal wastes.