Comparative water quality assessment between a young and a stabilized hydroelectric reservoir in Aliakmon River, Greece.

In this work, a comparative study on the water quality characteristics of two in-line water reservoirs (artificial lakes) in Aliakmon River (Western Macedonia, Greece) is performed. Polyfytos Reservoir and Ilarion Reservoir were created in 1975 and 2012 respectively, in order to serve the homonymous hydroelectric stations. In young artificial lakes, severe deterioration of water quality may occur; thus, the monitoring and assessment of their water quality characteristics and their statistical interpretation are of great importance. In order to evaluate any temporal or spatial variations and to characterize water quality of these two in-line water reservoirs, water quality data from measurements conducted from 2012 to 2015 were statistically processed and interpreted by using a modified National Sanitation Foundation water quality index (WQI). The water physicochemical characteristics of the two reservoirs were found to be generally within the legislation limits, with relatively small temporal and spatial variations. Although Polyfytos Reservoir showed no significant deviations of its water quality, Ilarion Reservoir exhibited deviations in total Kjeldahl nitrogen, nitrite nitrogen, total suspended solids, and turbidity due to the inundated vegetation decomposition. The conducted measurements and the use of the modified NSFWQI revealed that during the inundation period of Ilarion Reservoir, its water quality was "moderate" and that the deviations were softened through time, leading to "good" water quality during its maturation period. Three years since the creation of Ilarion Reservoir, water quality does not match that of Aliakmon River (feeding water) or that of the stabilized reservoir (Polyfytos Reservoir), whose quality is characterized as "high." The use of a WQI, such as the proposed modified NSFWQI, for evaluating water quality of each sampling site and of an entire water system proved to be a rapid and relatively accurate assessment tool.

Particulate organics degradation and sludge minimization in aerobic, complete SRT bioreactors.

The study evaluates the assumption that in activated sludge processes and under specific operating conditions, the considered unbiodegradable particulate organic fractions of influent (XU) organic solids and biomass decay residues (cell debris, XE) are degraded. The evaluation was performed by comparing sludge observed yield (Yobs) evolution in two full scale, complete solids retention time (SRT), aerobic bioreactors, to the predictions of two activated sludge models. The results showed that in steady state operating conditions of complete solids retention AS processes very low solids accumulation occur. In these conditions, solids accumulation is slightly affected by kinetic coefficients and significantly affected by XU and XE degradation rates. High endogenous residues degradation rate values of 0.05 d(-1) and 0.02 d(-1) were estimated for the two bioreactors, resulting in low solids accumulation, calculated at 1.6 tons and 3.59 tons per year respectively, of which 1.37 and 0.87 tons were non volatile suspended solids. Depending on WWTP operating conditions the endogenous residues degradation rate is the limiting factor of solids accumulation and consequently for particulate organics degradation.

Uncertainty in spectrophotometric analysis--"error propagation break up", a novel statistical method for uncertainty management.

In this work, is given the Combined Standard Uncertainty (CSU) calculation procedure, which can be applied in spectrophotometric measurements. For the assessment of the computations, different approaches are discussed, such as the contribution to the Combined Standard Uncertainty of the reproducibility, the repeatability, the total bias, the calibration curve, and the type of the measurand. Results of inter-laboratory measurements confirmed the assumptions. For the minimization of the errors propagation a controlled experimental procedure was applied by this laboratory, called "errors propagation break-up" (ERBs). The uncertainty of sample concentration from a reference curve dominates the Combined Standard Uncertainty. The contribution of the method and the laboratory bias (total bias) to the CSU is insignificant under controlled conditions of a measurement. This work develops a simple methodology that can be utilized to evaluate the uncertainty and errors control on routine methods used both by academic researchers or the industrial sector.

Cesium-137 monitoring using lichens from W. Macedonia, N. Greece.

(137)Cs content in lichens and substrate (soil, bark) collected from W. Macedonia, Greece was measured 20 years after the Chernobyl reactor accident. Archive material from previous collections was also used for comparison and a diachronic estimation of the radio-contamination status. A gradual decrease was detected which depended on various factors such as the collected species, location, growth rate and substrate. Maximum accumulation capacity of (137)Cs was observed in epilithic lichens in comparison to epigeic or epiphytic ones. Furthermore, foliose or crustose lichens such as Parmelia sulcata, Xanthoria parietina, Xanthoria calcicola, Xanthoparmelia somloensis were more contaminated than filamentose at the same biotope. Among filamentose or fruticose species those with large surface area to biomass ratio e.g. Usnea sp. showed also greater accumulation capacity. Autoradiography revealed an amount of (137)Cs distributed more or less uniformly in lichen thalli. The high (137)Cs activities found in lichens 20 years after Chernobyl suggest that these primitive plants are effective, suitable and inexpensive biological detectors of the distribution and burden of fallout radionuclide fallout pattern.

Cesium-137 monitoring using mosses from W. Macedonia, N. Greece.

(137)Cs activities in mosses and substrate (soil, bark) collected from W. Macedonia, Greece were measured 20 years after the Chernobyl reactor accident. Archive material from previous studies was also used for comparison and diachronic estimation of the radio-contamination status. A gradual decrease was detected which depended on various factors such as the collected species, location, growth rate and substrate. Maximum accumulation capacity of (137)Cs was observed in the epilithic mosses in comparison to the epiphytic ones. The (137)Cs content in the bark of the two broad-leaved species (oak and fagus) was higher than that of the conifer (pinus). Bark specimens of about 50 cm height were in general more contaminated than those of 200 cm. Autoradiography revealed an amount of (137)Cs distributed more or less uniformly in moss thalli. The high (137)Cs activities found in mosses 20 years after Chernobyl suggest that these primitive plants are effective, suitable and inexpensive biological detectors of the distribution and burden of radionuclide fallout pattern.