BIODEGRADATION Composting packaging Composting is an increasingly important method for recycling municipal wastes. Input materials include not just garbage, lawn clippings, and other plant residue, but paper and biodegradable plastics from packaging material. U. Pagga and co-workers provide a detailed description of efforts under way to determine which materials are suitable for composting. German, European, and international organizations are developing standards on the degradability and compostability of polymeric materials. The authors discuss test methods to determine that compost derived from these materials meets strict German and European standards. The methods eventually will be used to develop packaging materials for German food products. {J. Environ. Polym. Degrad. 1996, 4, 173-78)
PCBs in sediments River sediments in industrialized regions may contain high levels of PCBs, which pose an environmental and human health threat. Hudson River sediments in New York State have been heavily contaminated by PCBs and have been the subject of much research aimed at the remediation of PCB levels. K. M. Fish studied the biotransformation of PCBs in sediments by using a laboratory test tube system. He evaluated the effect of various concentrations of Aroclor 1242 on reductive dechlorination and subsequent aerobic biodegradation of PCBs. Results indicate that increasing levels of Aroclor accelerated reductive dechlorination and subsequent aerobic biodegradation of PCB after a lag period. This work shows that natural processes have a significant potential for attenuating PCB sediment concentrations. {Appl. Environ. Microbiol. 1996, 62, 3014-16)
BIOREMEDIATION Optimizing anaerobic systems Low costs have made anaerobic biodegradation an increasingly popular method for in situ treatment of environmental pollutants, especially chlorinated organic compounds.
Heavy metal ions that accompany organic pollutants, however, often interfere with the process. C-W. Kuo and colleagues investigated the effect of metal ions on the metabolism of bacteria that degrade 2-chlorophenol and 3-chlorobenzoate. They added ions of cadmium, copper, chromium, and mercury at concentrations of 0.01-100 ppm. The metals had differential effects on dehalogenation, aromatic degradation, and methanogenesis in the bacteria. The results suggest a strategy for optimizing anaerobic biodegradation by characterizing heavy metals present in a contaminated site. {Appl. Environ. Microbiol. 1996, 62, 2317-23)
Surfactant benefits Surfactants offer the potential for increasing the solubility of environmental contaminants in water, making them more available to microorganisms involved in biodegradation. S. J. Grimberg and colleagues investigated the biodegradation of phenanthrene, a common polycyclic aromatic hydrocarbon (PAH), in the presence of a nonionic surfactant. The study involved the surfactant Tergitol NP-10 and its influence on the biodegradation of solid-phase phenanthrene by Pseudomonas stutzeri P16. Results indicate that the surfactant increased bacterial growth rates by making phenanthrene more soluble. A combined biodegradation and dissolution model successfully predicted the experimental observations. This work demonstrates the potential for enhanced PAH biodegradation using surfactants and suggests that the model may be useful in system engineering and design. (Appl. Environ. Microbiol. 1996, 62, 2387-92)
DRINKING WATER Canadian Giardia The prevalence of Giardia cysts and Cryptosporidium oocysts in Canadian drinking water has not been well characterized. P. M. Wallis and colleagues determined the prevalence of Giardia and Cryptosporidium and characterized Giardia spp. in Canadian drinking water supplies. Nationwide samples of raw sewage, raw water, and drinking water were examined. Results indicate that Giardia cysts are commonly found in all
three types of water throughout Canada. Cryptosporidium oocysts are also found but are less common. An action level for Giardia cysts in Canadian drinking water supplies has been proposed as a result of this Work. [Appl. Environ. Microbiol. 1996, 62, 2789-97)
Coliform regrowth Regrowth of fecal coliform bacteria in treated drinking water is the most common reason for violation of federal and state drinking water standards. Yet little is known about what causes coliform regrowth in water pipes and distribution systems. M. W. LeChevallier and colleagues investigated 31 water systems in North America during an 18-month period. They concluded that coliform regrowth within a distribution system depends on complex interactions among many factors. These include filtration, temperature, disinfectant type, disinfectant levels, assimilable organic carbon (AOC) levels, corrosion control, use of phosphate-based corrosion inhibitors, and use of unlined cast iron pipe. The authors conclude that water utilities must look at all these factors when trying to solve regrowth problems. {Appl. Environ. Microbiol. 1996, 62, 2789-97)
Filtering viruses There is growing awareness that conventional drinking water treatment processes do not always inactivate disease-causing viruses. N. Kawabata and co-workers have developed a filtration membrane that is highly effective in removing viruses and could supplement conventional chlorination. The membrane consists of minute beads of cross-linked poly(AT-benzyl-4-vinylpyridinium chloride) reinforced by nonwoven cloth. Simple filtration with one sheet of the material removed 99.96-99.9995% of the virus bacteriophage T4. With two sheets of the membrane, the virus was undetectable. In contrast, conventional ultrafiltration using 1-3 sheets of cellulose nitrate membrane coated with poly(AT-benzyl-4-vinylpyridinium chloride) removed 99.4-99.998% of the virus. {J. Appl. Polym. Sci. 1996, 60,911-17)
Pasteurization treatment Infection with Cryptosporidium parvum oocysts has been documented
VOL. 31, NO. 1, 1997 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 7 A
