Tuesday, 11 April 2017

We Should Expect More out of Our Sewage Sludge

Below are some of the highlights from this important, recent assessment of land disposed Sewer Sludge - in the end, the conclusion these independent professors come to is simple: “ We do not advocate the continuation of land application”

Professors - Jordan Peccia*† and Paul Westerhoff‡

† Department of Chemical and Environmental Engineering, Yale University, Mason Laboratory, 9 Hillhouse Avenue, P.O. Box 208286, New Haven, Connecticut 06520, United States ‡ School of Sustainable Engineering and The Built Environment, Arizona State University, Box 3005, Tempe, Arizona 85287-3005, United States - Environ. Sci. Technol., 2015, 49 (14), pp 8271–8276 DOI: 10.1021/acs.est.5b01931 Publication Date (Web): June 24, 2015 Copyright © 2015 American Chemical Society

Hazardous Chemical and Pathogen Content

Words that start with the letters “slu” do not usually connote something with a positive public image. Sewage sludge is no exception. Sludge is a record of what society excretes. This includes any pathogen that is contained in human feces, urine, and vomitus. A recent study found more than 27 different forms of human viruses in the sewage sludges of five large U.S. cities, ranging from Adenovirus to Corona virus to HIV.(1) Antibiotic resistant bacteria and antibiotic resistance genes are common in wastewater and biosolids.(2, 3) Stabilization is meant to reduce this pathogen load, usually by 1–2 orders of magnitude for class B treatments. Microbial risk analyses, which have typically shown limited risk to residents for Salmonella spp. and Enterovirus(4) have recently suggested significantly increased risk of infection due to emerging viruses such as Norovirus.(6) Metals and organic chemicals that resist biological mineralization can sorb to solid particles and also accumulate in sludge. These include polybrominated flame retardants, pharmaceuticals like Prozac and Tagamet, human hormones such as estrogen, antibiotics, narcotics including cocaine, and the metabolites of these compounds.(8, 9) Class B land application can include spreading tons of sludge per acre of land, producing a strong odor and attracting disease vectors. The chemical and microbial content and sludge odor are important drivers to the public resistance to land application.(10) Land application disputes are a large source of litigation and hundreds of human health complaints from residents living near land application sites have been logged.(11) More so than regulations, costs, or environmental concerns, those that manage biosolids land application programs cite concerns from neighbors, environmental groups, and others as the top pressures on their programs.(7)

Converting Infrastructure to Extract Value from Sludge

Sludge is the receptor of wastewater’s contaminants. It may not ever be feasible to treat the product to a level that contains no pathogens, no toxins, no hazardous chemicals, and no odors, and can be spread back into the environment with no public objections. Based on the above analysis, the more economical, socially acceptable, and environmentally sustainable approach may be to exploit sewage sludges for metals, nutrients, and energy.

Energy Recovery

One approach capable of achieving several treatment and recovery goals for biosolids would be combustion-based technologies associated with incineration, gasification or liquifaction. Combustion can destroy pathogens and mineralize persistent organic chemical contaminants, while producing energy and concentrating valuable metals and inorganic chemicals.

Conclusions: We Should Expect More

Sludge management is a central component of water quality engineering. Regardless of the approach to treating wastewater, primary and secondary sludge will be produced. A future that is concerned with economics, water usage, energy conservation, beneficial reuse, recycling and environmental health will demand more of sewage sludge. We do not advocate the continuation of land application, as it has limited social and economic sustainability

The whole paper can be read here - http://pubs.acs.org/doi/full/10.102...