Direct toxicity assessment of wastewater is becoming necessary, and new legislation may render it compulsory for the water industry. At present such assessment is performed at a laboratory away from a site, at considerable cost, and results often come too late, after a toxic event has occurred and the toxin has been released into the environment. Some of the rapid toxicity tests available today require certain conditions to function properly, or their results do not always correlate with other methods. The objective of this study was to assess a portable device, the Baroxymeter, for its suitability as an instrument to test wastewater toxicity. The way the device works is based on monitoring respiration of a bacterial culture by pressure measurements and using respiration inhibition as a toxicity alert. It has been shown that it is possible to detect toxic substances such as 3,5-dichlorophenol and bronopol within 5 min from a 1-mL sample. The benefits and future applications of the Baroxymeter as a high-throughput, cost-effective alternative for toxicity screening are discussed in this article.

Odours from sewage treatment works are a significant source of environmental annoyance. There is a need for tools to assess the degree of annoyance caused, and to assess strategies for mitigation of the problem. This is the role of odour modelling. Four main stages are important in the development of an odour problem. Firstly, the odorous molecules must be formed in the liquid phase. They must then transfer from the liquid to the gaseous phase. They are then transported through the atmosphere to the population surrounding the odour source, and are then perceived and assessed by that population. Odour modelling as currently practised tends to concentrate on the transportation of odorants through the atmosphere, with the other areas receiving less attention. Instead, odour modelling should consider each stage in an integrated manner. This paper describes the development of integrated odour models for annoyance prediction. The models describe the liquid-phase transformations and emission of hydrogen sulphide from sewage treatment processes. Model output is in a form suitable for integration with dispersion models, the predictions of which can in turn be used to indicate the probability of annoyance. The models have been applied to both hypothetical and real sewage treatment works cases. Simulation results have highlighted the potential variability of emission rates from sewage treatment works, resulting from flow, quality and meteorological variations. Emission rate variations can have significant effects on annoyance predictions, which is an important finding, as they are usually considered to be fixed and only meteorological variations are considered in predicting the odour footprint. Areas for further development of integrated odour modelling are discussed, in particular the search for improved links between analytical and sensory measurements, and a better understanding of dose/response relationships for odour annoyance.