Performance of three small-scale wastewater treatment plants. A challenge for possible re use.

The study focused on the assessment of the performance of three WWTPs in Greece by the estimation of the microbiological and chemical quality of influent and effluent sewage. Physicochemical parameters were recorded (temperature, pH, COD, BOD, suspended solids, conductivity), and meteorological data were collected (air temperature, rain). Microbiological parameters were analyzed (Escherichia coli, total coliforms, bacteriophages, Salmonella, human adenoviruses, Candida, Pseudallescheria boydii, helminths, parasites Cryptosporidium ssp., and Giardia spp.). Statistically significant correlations among the various aforementioned parameters were investigated, in an attempt to propose appropriate processing performance indicators. Furthermore, the study aimed to assess current joint ministerial decision (JMD) on wastewater reuse, for irrigation purposes; to evaluate its practicability and its potential for public health protection. In the vast majority, outlet samples from all three studied WWTPs were not appropriate for irrigation reuse purposes based on BOD50 and suspended solids limit values, set by the current JMD, for both limited and unrestricted irrigation applications. Reductions for E. coli, total coliforms, and bacteriophages were found to range between 2-3, 1.5-2.5, and 2-4 log10 values, respectively. Salmonella spp. was detected in outlet sewage samples from Patra (PAT), Arachova (ARH), and Livadeia (LEV), at 23% (3/13), 33% (4/12), and 38% (5/13), respectively. Molds were detected at 92.3% (12/13), 100% (13/13), and 91.6% (11/12), respectively, while Candida was found at 85% (11/13), 67% (8/12), and 46% (6/13). A high prevalence of Pseudallescheria boydii, in outlet samples from all studied WWTPs is an important public health issue, which underlines the need for further studies on this emerging fungal pathogen in wastewater reuse applications. Pseudallescheria boydii was found at 85% (11/13), 67% (8/12), and 46% (6/13), respectively. Helminths were found in both inlet and outlet samples, of all studied WWTPs, at 100%. Human adenoviruses, were detected at high percentages in outlet samples at 76.9% (10/13), 92.3% (12/13), 84.6% (11/13), respectively, while no influence of UV irradiation was recorded on the entry and exit loads of human adenoviruses. No influence of meteorological parameters was found on the microbiological and chemical parameters, with the exception of a weak positive correlation between environmental temperature and bacteriophages. A moderate positive correlation was found between BOD and suspended solids, bacteriophages, and total coliforms, bacteriophages and E. coli, and bacteriophages and adenoviruses. A significant positive correlation was found between total coliforms and E. coli, COD and BOD, and suspended solids and COD. No correlations were proved between human pathogens and bacterial indicator parameters. Collectively, our findings underlined the unsuitability of the current JMD on wastewater reuse in Greece, or public health protection. The study is expected to support the development of a public health risk assessment model based on quantitative risk assessment on the use of treated wastewater for irrigation purposes in Greece.

Equivalency testing of TTC Tergitol 7 agar (ISO 9308-1:2000) with five culture media for the detection of E. coli in water samples in Greece.

In this study ten laboratories in Greece compared the performance of reference method TTC Tergitol 7 Agar (with the additional test of beta-glucuronidase production) with five alternative methods, to detect E. coli in water, in line with European Water Directive recommendations. The samples were prepared by spiking drinking water with sewage effluent following a standard protocol. Chlorinated and non-chlorinated samples were used. The statistical analysis was based on the mean relative difference of confirmed counts and was performed in line with ISO 17994. The results showed that in total, three of the alternative methods (Chromocult Coliform agar, Membrane Lauryl Sulfate agar and Trypton Bilex-glucuronidase medium) were not different from TTC Tergitol 7 agar (TTC Tergitol 7 agar vs Chromocult Coliform agar, 294 samples, mean RD% 5.55; vs MLSA, 302 samples, mean RD% 1; vs TBX, 297 samples, mean RD% -2.78). The other two alternative methods (Membrane Faecal coliform medium and Colilert 18/ Quantitray) gave significantly higher counts than TTC Tergitol 7 agar (TTC Tergitol 7 agar vs MFc, 303 samples, mean RD% 8.81; vs Colilert-18/Quantitray, 76 samples, mean RD% 18.91). In other words, the alternative methods generated performance that was as reliable as, or even better than, the reference method. This study will help laboratories in Greece overcome culture and counting problems deriving from the EU reference method for E. coli counts in water samples.

Treated water quality assurance and description of distribution networks by multivariate chemometrics.

Throughout the year 2007, 89 treated water samples from three water treatment plants (WTPs) of the Athens Water Supply and Sewerage Company (EYDAP S.A.) and 180 samples from network tanks (NWTs) were analyzed for electrical conductivity (EC), alkalinity (TA), pH, aluminium (Al), total hardness (TH), chloride (Cl(-)), residual chlorine (free Cl), calcium (Ca(2+)) and magnesium (Mg(2+)). The results regarding the WTPs were subjected to a principal component analysis (PCA) with 75% of the total variance being explained. A stepwise linear discriminant analysis (LDA) model constructed from the 89 treated water samples was used to predict class membership of the samples from the NWTs with a view to estimating the propagation of a possible water quality deterioration originating from the WTPs. The model utilized Cl(-), Al and EC and yielded a 96% correct classification of the training dataset, whereas the cross-validation yielded a 94% correct classification. Network tank samples were 95% correctly classified with regard to their theoretically expected origin. The stepwise discriminant analysis based on separate covariance matrices of the canonical discriminant functions yielded a 98% correct classification of both the training dataset and the network tank samples. The classification and regression tree (C&RT) algorithm showed that the main parameters used in the discrimination of the WTP samples were EC and Al. The post-hoc classification of the training dataset was 99%, whereas 88% of NWT samples were correctly classified.