November 2011, Vol. 23, No.11

Research Notes

Pathogen that causes disease in coral comes from human waste

Researchers have identified human wastewater as a source of a pathogen that causes white pox in Caribbean elkhorn coral. Since 2002, researchers have known that the pathogenic bacterium Serratia marcescens has been killing the coral. The bacteria are a species found in both human and animal waste, according to a University of Georgia (Athens) news release.

A team from Rollins College (Winter Park, Fla.) and the University of Georgia collected human samples from both a wastewater treatment facility in Key West, Fla., and several animals, including deer and seagulls, in Key West. After performing genetic analyses, the researchers were able to distinguish human from animal strains and identified that only the human strain matched the bacteria found in white-pox-afflicted corals, the release says.

The team confirmed the findings by inoculating fragments of coral with the human strain. The experiments, funded through Florida’s Mote Marine Laboratory “Protect Our Reefs” grant program, were performed in a laboratory in closed seawater tanks to eliminate any risk of infection to wild coral populations, the release says.

“The strain caused disease in elkhorn coral in 5 days, so we now have definitive evidence that humans are a source of the pathogen that causes this devastating disease of corals,” said Kathryn P. Sutherland, associate professor of biology at Rollins College, according to the release. The study’s authors include Sutherland and Sameera Shaban of Rollins College, as well as Erin K. Lipp, Jessica L. Joyner, and James W. Porter of the University of Georgia.

Serratia marcescens causes respiratory, wound, and urinary tract infections; meningitis; and pneumonia in humans. This research is the first documented occurrence of a human disease causing population declines in marine invertebrates, the news release says.

But Porter explained that this problem can be solved with advanced wastewater treatment. The Florida Keys area is in the process of upgrading local wastewater treatment plants to eliminate this source of the bacterium, the release says.

Elkhorn coral was listed for protection under the U.S. Endangered Species Act in 2006, largely due to white pox disease, the news release says.

The research was published in the journal PLoS ONE. Read more at http://dx.plos.org/10.1371/journal.pone.0023468.

The team currently is funded by a $2.2 million grant from the U.S. National Science Foundation to investigate the ecology of the white pox disease in the Florida Keys. During the 5-year study, the researchers will study the mechanisms of transmission of the coral pathogen and factors driving the white pox outbreaks, such as water quality, climate variability, and patterns of human population density, the news release says. 

Plastic bottles remove arsenic from drinking water

A new process shows that plastic bottles coated with the amino acid cysteine can remove arsenic from drinking water. The new process was presented at the National Meeting and Exposition of the American Chemical Society (ACS; Washington, D.C.) in August.

Tsanangurayi Tongesayi, professor of analytical and environmental chemistry at Monmouth University (West Long Branch, N.J.), led the study to develop a simple, cheap, and environmentally friendly method to remove arsenic from water, according to the abstract of a research report on the project.

Arsenic, a toxic human carcinogen, is odorless, tasteless, and colorless. It enters drinking water from natural deposits in soil and rock and from agricultural and industrial sources, according to an ACS news release. Drinking water remains one of the most significant routes of arsenic exposure to humans, and technologies to reduce arsenic levels in drinking water are mostly inaccessible in developing countries because of their costs and operational complexities, the abstract says.

“Our process uses pieces of plastic water, soda pop, and other beverage bottles,” Tongesayi said in an ACS news release. “Coat the pieces with cysteine — that’s an amino acid found in dietary supplements and foods — and stir the plastic in arsenic-contaminated water. This works like a magnet. The cysteine binds up the arsenic. Remove the plastic and you have drinkable water.”

To test the method, cysteine molecules were attached to pieces of plastic cut from water bottles and used to remove arsenic from synthetic water samples in a batch process. The process takes advantage of the affinity of metals and metalloids to thiol groups, the abstract says.

Laboratory testing of this method on water containing 20 ppb of arsenic — which is two times the safe standard set by the U.S. Environmental Protection Agency for drinking water — produced water with 0.2 ppb of arsenic, the news release says.

The technology is designed to use locally available materials and to be straightforward, so that people without technical skills but some training can use it, Tongesayi said in the news release. Discarded plastic bottles often are available in abundance in developing countries, and the application of cysteine does not require complicated technology.

Tongesayi is working to develop a largescale system using the technology, he said during a news briefing at the ACS meeting. A video of the briefing is accessible at www.ustream.tv/recorded/16989574.

Tongesayi has submitted the technology, which also has the potential to remove other heavy metals from drinking water, for a patent and is seeking funding or a commercial partner to move the arsenic removing process into use quickly, the release says. 

September WER examines sudden increase and regrowth

The September issue of Water Environment Research (WER) reports on how experts tested the effect of several digestion and dewatering processes on the sudden increase and regrowth of fecal coliform and Escherichia coli in anaerobically digested biosolids.

“This is an important question for biosolids disposal, since many of the available alternatives depend on compliance with strict limits based on indicator organisms,” said Michael Stenstrom, WER executive editor.

Sudden increase refers to higher densities of indicator bacteria that occur immediately after dewatering; regrowth refers to densities of indicator bacteria that occur during storage over longer periods, according to the article.

The researchers collected biosolids samples from 10 full-scale wastewater treatment plants using either centrifuge or belt filter press dewatering. By sampling the different processes, the effect of digestion temperature, reactor configuration, and dewatering processes on sudden increase and regrowth could be investigated, the article states.

In general, sudden increase typically was observed in the thermophilic processes with centrifuge dewatering but not in the mesophilic processes with either centrifuge or belt filter press dewatering. Regrowth was observed in both thermophilic and mesophilic processes with centrifuge dewatering but not with belt filter press dewatering, the article states.

The article contains in-depth results of each biosolids sample, as well as a discussion of the findings’ implications.

The article, “The Effect of Digestion and Dewatering on Sudden Increases and Regrowth of Indicator Bacteria after Dewatering,” appears in the September WER and can be downloaded free at bit.ly/pirWdZ.

 

Water Environment Research allows open access to one article per issue on a range of important technical issues such as nutrient removal, stormwater, and biosolids recycling. Find more at www.ingentaconnect.com/content/wef/wer.  

  

 

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