Browsing by Author "Stuetz, Richard"

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    Fate and removal of pharmaceuticals during sewage treatment
    (Cranfield University, 2005-10) Thompson, Andrew; Cartmell, Elise; Stuetz, Richard
    Pharmaceuticals, personal care products and their metabolites are continuously entering the environment through many routes, especially from the effluent of sewage treatment plants. The aim of this work was to examine the fate and removal of pharmaceuticals during sewage treatment, and establish ways in which current sewage treatment technologies could be optimised to improve removal. Based on an analysis of pharmaceutical usage and environmental effects, four compounds were selected for further study (triclosan, tetracycline, carbarnazeptrine, and caffeine). Reliable analytical methods Were developed, using . HPLC-UV, to detect these compounds in sewage samples. The amounts of removal of the four compounds were quantified using laboratory sorption and biodegradation tests. Both tetracycline and triclosan were shown to be readily biodegradable, and to sorb strongly to biomass, although sorption occurred at different rates. Caffeine degraded rapidly, but did not sorb to biomass, whilst carbarnazepine did not sorb or biodegrade. Grab samples were taken before and after every major process unit at four sewage treatment plants (STPs). Although tetracycline was not detected in any samples, triclosan was measured at concentrations up to 5115 rig I-1, caffeine was measured at concentrations up to 82,300 ng C., and carbarnazeptne was measured at concentrations up to 1461 rig 1-1. This is the first time carbarnazepine and caffeine concentrations have been reported in UK sewage. The grab samples showed that a wide range of pharmaceutical effluent concentrations can be expected. The concentrations of the pharmaceuticals detected in this research were not high enough to cause immediate harm (i.e. death) to aquatic organisms. However, there is insufficient information to determine whether exposure to these low concentrations, typically around PNEC levels, may have an effect over a long period of time. Further composite sampling conducted at one STP generated data, modelled using Toxchem-1-, which demonstrated how variations in a wide range of parameters were correlated with the removal of pharmaceuticals. These showed that whilst sludge age may be the most important parameter, pH, temperature, hydraulic retention time, and chemical oxygen demand could have a critical effect on the removal of pharmaceuticals. Several ways of optimising sewage treatment plants have been proposed, including pH adjustments and longer HRTs to enhance sorption, as well as a novel adaptation to activated sludge tanks incorporating two WAS type bioreactors to enhance biodegradation. The effects of plant operating events, such as aeration failures, were also investigated. These showed that a typical length of aeration loss (four hours) could result in reduced pharmaceutical removal (through decreases in both sorption and biodegradation) for up to twelve hours. Overall, this work has shown that it may be possible to adapt current sewage treatment technology to improve removal of pharmaceuticals which sorb or biodegrade readily. With further research, these adaptations could become a viable alternative to tertiary treatment technologies such as ozonation, granular activated carbon, or chlorine dioxide
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    Inlet monitoring of a potable water supply using a sensor array
    (Cranfield University, 2003-10) Hogben, Peter James; Stuetz, Richard
    Monitoring for pollutants in potable water is an area of interest and concern for water supply companies. Supply of sub-standard water can draw complaints from public and industrial customers. Water and water tainted with pollutants were used to assess the application of a non-specific chemical sensor array (eNose) to monitor for changes in the headspace generated from a flow-cell by means of statistically designed experiments. 2-chlorophenol and diesel were used to further assess trends in headspace generation during trials where different combinations of sampling parameters were applied. Field trials were conducted in accordance with the most suitable methodology determined during initial studies under laboratory conditions. The headspace is generated by bubbling nitrogen through the flow-cell containing a water sample. The liquid sample is flushed and regenerated after each sensor acquisition cycle. The resultant headspace sample is transferred to the sensor array module where the resistance of the conducting polymer sensors is monitored as they are exposed to each respective headspace sample. The change in each sensor resistance after 60 seconds of exposure is used to represent the headspace character. Subsequent acquisitions are added to a data set and then presented graphically. Sudden changes in the sensor resistance plots represent changes in water quality. The results showed that the developed apparatus and sampling methodology can determine the presence or absence of pollution in a water matrix. Laboratory analysis showed that detection levels for 2-chlorophenol and diesel were both <5 ppm in the mixed stream. Future developments should focus on increasing the sensitivity of the system by concentrating the pollutants in either the liquid or gas phase or by modifying the sampling protocol to enable sensor recognition at lower concentration levels. The sensor array could act as a screening technique to support quantitative and characterising analytical equipment at the abstraction point. Establishing a pollution alarm limit, within the bounds of acceptable system variation, would enable conventional analytical techniques to remain on standby until activated by a statistically significant change in water quality. Once established continued testing would enable alarm levels to be incorporated into a contaminant database for additional pollutant compounds and combinations of known taste and odour causing compounds.
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    On-line monitoring of wastewater quality using a chemical sensor array
    (Cranfield University, 2002-12) Bourgeois, Wilfrid; Stuetz, Richard
    Real-time and on-line monitoring of wastewater quality is a subject of growing concern both in the United Kingdom and internationally. Global organic load parameters are traditionally used to define wastewater characteristics and to demonstrate that a wastewater treatment plant meets statutory law. However these measurements are mainly based on sample collection and retrospective analysis which can be time consuming. Existing on-line instruments remain limited by environmental factors, short lifetimes and fouling problems due to the harsh environment in which they have to be located. The recent availability of commercial sensor array instruments could offer a rapid and relatively simple technique for non-invasive monitoring. Cont/d.