Variability of Toxic Trace Contaminants in Municipal Sewage Treatment Plants

Abstract

The variability of toxic trace contaminants in influents and effluents at three full-scale municipal sewage treatment plants was measured by collecting grab samples of degritted raw wastewater and non-chlorinated secondary effluent at two hour intervals over eight consecutive days. The samples were analyzed for metals, conventional contaminants and a range of organic trace contaminants. The metals and volatile organic compounds were the dominant contaminants found in the influents. In the effluents, organic concentrations were close to detectable levels and polyaromatic hydrocarbons were almost never detected. Some influent metal and organic contaminants varied diurnally while others appeared to fluctuate randomly with periodic spike inputs. The variability of most effluent trace contaminant concentrations was considerably attenuated in comparison to influent concentrations.

Evaluation of an Automatic Composite Sampler for Volatile Organic Compounds in Raw Wastewater

“…The compounds observed and their concentrations are consistent with results from previous monitoring of VOCs in the Metropolitan plant influent wastewater 8,9 and with data from other treatment plants. 7 VOC concentrations determined by the grab sampling and composite sampling methods were generally in close agreement. On October 19, 1995, the mean concentrations of trichloroethene, tetrachloroethene, and toluene observed in the composite samples were 15-20% higher than the mean concentrations of the grab samples (Table 1).…”

“…Influent VOC concentrations vary widely over time in response to varying patterns of domestic, commercial, and industrial discharge in the service area. 7,8 Thus, a single grab sample, or even a limited series of grab samples will not be likely to produce a representative estimate of the daily VOC loading. A composite sample collected over 24 hours could be representative, assuming the sampling frequency was sufficient to accurately represent periods of rapid variation in the VOC concentrations.…”

The Inputs of POPs into Soils by Sewage Sludge and Dredged Sediments Application

“…The application of sewage sludge on agricultural soils is connected with following facts: -increasing amounts of sewage sludge thanks to intensive waste water treatment -the characteristic of sludge as the material with increased content of organic matter and nutrients The application of sludge into soil could lead to an increase of the contents of organic matter or macro elements, but the contamination by potentially risky elements and persistent organic pollutants could be relevant also. The problems connecting with increased persistent organic pollutants (POPs) contents in sewage sludge were confirmed by many authors (Markard, 1988;Melcer et al, 1988;Starke, 1992;Oleszczuk, 2007;Clarke et al, 2008;Natal-da-Luz et al, 2009). The load of soil by POPs after sludge application can influence their transfer into food chains (Passuello et al, 2010).…”

Recommended maximum contents of persistent organic pollutants in sewage sludge for application on agricultural soils

“…Many authors documented the positive effects of the sludge application on the yield and soil organic mater and the problem of potentially risk elements (Melcer et al 1988, Balík et al 1999, Hanč et al 2005. In his previous article, Vácha et al (2005a) documented that some foreign institutes deal with long-term research of persistent organic pollutants in sludge (Markard 1988, Witte 1988, Starke et al 1991, Webber and Singh 2001.…”