Behavioural and Physiological Responses of Gammarus pulex Exposed to Cadmium and Arsenate at Three Temperatures: Individual and Combined Effects

This study aimed at investigating both the individual and combined effects of cadmium (Cd) and arsenate (AsV) on the physiology and behaviour of the Crustacean Gammarus pulex at three temperatures (5, 10 and15°C). G. pulex was exposed during 96 h to (i) two [Cd] alone, (ii) two [AsV] alone, and (iii) four combinations of [Cd] and [AsV] to obtain a complete factorial plane. After exposure, survival, [AsV] or [Cd] in body tissues, behavioural (ventilatory and locomotor activities) and physiological responses (iono-regulation of [Na+] and [Cl−] in haemolymph) were examined. The interactive effects (antagonistic, additive or synergistic) of binary mixtures were evaluated for each tested temperature using a predictive model for the theoretically expected interactive effect of chemicals. In single metal exposure, both the internal metal concentration in body tissues and the mortality rate increased along metallic gradient concentration. Cd alone significantly impaired both [Na+] and [Cl−] while AsV alone had a weak impact only on [Cl−]. The behavioural responses of G. pulex declined with increasing metal concentration suggesting a reallocation of energy from behavioural responses to maintenance functions. The interaction between AsV and Cd was considered as ‘additive’ for all the tested binary mixtures and temperatures (except for the lowest combination at 10°C considered as “antagonistic”). In binary mixtures, the decrease in both ventilatory and locomotor activities and the decline in haemolymphatic [Cl−] were amplified when respectively compared to those observed with the same concentrations of AsV or Cd alone. However, the presence of AsV decreased the haemolymphatic [Na+] loss when G. pulex was exposed to the lowest Cd concentration. Finally, the observed physiological and behavioural effects (except ventilation) in G. pulex exposed to AsV and/or Cd were exacerbated under the highest temperature. The discussion encompasses both the toxicity mechanisms of these metals and their interaction with rising temperature

Evaluation of toxic properties of industrial wastewater using on-line respirometry

An on-line respirometric biosensor using activated sludge microorganisms was used in this work for the assessment of toxic properties of industrial effluents and for the evaluation of their effect on the performance of a municipal wastewater treatment plant. Continuous monitoring of combined industrial discharges was carried out for a period of six months, and increased toxicity values were observed during the evening times and the weekends, possibly due to the discharge of partially treated wastewaters from certain processing units. Furthermore, no direct correlation was observed between toxicity values and organic content, indicating that simply monitoring organic load, as it usually happens in most wastewater treatment plants, does not help in predicting the toxic properties of the effluent. Therefore, the installation and operation of an on-line respirometer is required, in combination with chemical analysis, for the protection of the operation of a municipal wastewater treatment plant from toxic shocks. The assessment of toxicity of wastewaters from certain industrial plants showed that bioluminescence inhibition on Vibrio fischeri was generally higher than the respirometric inhibition onactivated sludge microorganisms. It was concluded that for the evaluation of potential toxicity of influents on a wastewater treatment plant, activated sludge microorganisms should be preferred as test species

Testing industrial effluents with bioassays in Greece

The primary aim of this study is the investigation of a suitable bioassay that could be potentially correlated to respirometric techniques in order to evaluate industrial wastewater toxicity. Three microbiotests, the crustacean Daphnia magna test, the marine bacterium Vibrio fischeri test and protozoan Tetrahymena thermophila test, were used in order to investigate their potential correlation with a respirometric technique. It was found that the Tetrahymena thermophila test correlates best with respirometric techniques. The toxicities of the effluents of three different groups of industries, located in Thessaloniki, Greece, metal coating, food and dying industries, were also tested

Economical and social aspects: Evaluation of incorporation potential in municipal wastewater reuse procedure in Greece

It is the objective of this study to evaluate the incorporation potential of economic and social factors in municipal wastewater reuse procedure, aiming at determining whether it is worthwhile for a municipality to construct the necessary advanced treatment systems or not. Advanced wastewater treatment is the additional treatment needed to remove any constituents remaining after conventional secondary treatment and it is considered necessary when there is plan for treated wastewater reuse. Economic and social factors, as well as the necessary environmental factors, could be used as the main parameters, which will serve in the development of an evaluation model. This model could be based in a cost-benefit analysis which, through a correlation procedure, can lead to an optimal solution adoption. This model could be useful for many municipalities in Greece, where wastewater reuse does not consist presently a common method of treated wastewater management