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Temporal variability of sewage sludge heavy metal content from Greek wastewater treatment plants

Spanos T., Ene A., Patronidou C. S., Xatzixristou C.

Ecological Chemistry and Engineering. S

2016

Vol. 23, nr 2

271--283

The aim of this study was to evaluate the temporal variations of selected heavy metals level in anaerobic fermented and dewatered sewage sludge. Sewage sludge samples were collected in different seasons and years from three municipal wastewater treatment plants (WWTPs) located in Northern Greece, in Kavala (Kavala and Palio localities) and Drama (Drama locality) Prefectures. An investigation of the potential of sludge utilization in agriculture was performed, based on the comparison of average total heavy metal concentrations and of chromium species (hexavalent, trivalent) concentrations with the allowed values according to the Council Directive 86/278/EEC and Greek national legislation (Joint Cabinet Decision 80568/4225/91) guidelines. In this regard, all the investigated heavy metals (Cd, Cr, Cu, Ni, Pb, Zn, Hg) and chromium species Cr(VI) and Cr(III) have average concentrations (dry matter weight) well below the legislated thresholds for soil application, as following: 2.12 mg kg−1 Cd; 103.7 mg kg−1 Cr; 136.4 mg kg−1 Cu; < 0.2 mg kg−1 Hg; 29.1 mg kg−1 Ni; 62.0 mg kg−1 Pb; 1253.2 mg kg−1 Zn; 1.56 mg kg−1 Cr(VI) and 115.7 mg kg−1 Cr(III). Values of relative standard deviation (RSD) indicate a low or moderate temporal variability for domestic-related metals Zn (10.3-14.7%), Pb (27.9-44.5%) and Cu (33.5-34.2%), and high variability for the metals of mixed origin or predominantly resulted from commercial activities, such as Ni (42.4-50.7%), Cd (44.3-85.5%) and Cr (58.2-102.0%). For some elements the seasonal occurrence pattern is the same for Kavala and Palio sludge, as following: a) Cd and Cr: spring>summer>winter; b) Cu, Ni and Pb: winter>spring>summer. On average, in summer months (dry season) metal concentrations are lower than in spring and winter (wet seasons), with the exception of Zn. For Kavala and Palio the results demonstrate that the increased number of inhabitants (almost doubled) in summer time due to tourism does not influence the metal levels in sludge. Comparing the results obtained for similar spring-summer-winter sequences in 2007 and 2010/11 and for the spring season in 2007, 2008 and 2010, it can be noticed that, in general, the average heavy metal contents show an increasing tendency towards the last year. In all the measurement periods, the Palio sludge had the highest metal contents and Kavala sludge the lowest, leading to the conclusion that the WWTP operating process rather than population has a significant effect upon the heavy metal content of sludge. Cr(VI)/Cr(total) concentration ratios are higher for Kavala sludge in the majority of sampling campaigns, followed by Drama and Palio sludge. The metals which present moderate to strong positive correlation have common origin, which could be a domestic-commercial mixed source.

Chemometric evaluation of the air quality in an industrial region. Case study Kosice, Slovakia

Simeonova P., Simeonov V., Lux L., Dakova I., Spanos T.

Chemia i Inżynieria Ekologiczna

2005

Vol. 12, nr 7

727-737

The present case study deals with the environmetric estimation of the sir quality in the urban and rural region of City of Kosice, Slovakia. The annual loads of total dust and 8 heavy metals were used as input data. Correlation, cluster, and principal components analysis were used to classify, model and interpret the data. It bas been found that a distinctive separation between the rural and urban sites is observed (cluster analysis), which indicated different dynamics of the pollution at both sites. Further, the correlation gave some hints about possible linkages between the chemical tracers but without clarifying the structure of the data sets. Using principal components analysis and regression on principal components, it was found that three latent factors determine the pollution impact - soil or mineral dust, industrial and traffic sources. It was proved that differences are present for the rural and the urban sites in the source apportioning of the total trace metal concentrations. It made possible to discuss the different pollution patterns at the rural and at the urban sites.

Przedstawiono studium przypadku dotyczącego oceny środowiskowej jakości powietrza regionu koszyckiego, mającego charakter miejsko-wiejski. Danymi wejściowymi tej oceny były średnioroczne pomiary stężenia pyłu oraz 8 metali ciężkich. Do klasyfikacji, modelowania i interpretacji danych doświadczalnych zastosowano analizę: korelacji, klasterów oraz składników głównych. Za pomocą analizy klasterów stwierdzono wyraźne różnice między obszarem miejskim a wiejskim, wskazuje to na różnice w dynamice rozprzestrzeniania się zanieczyszczeń powietrza w tych dwóch obszarach. Analiza korelacji wskazuje na istnienie zależności między badanymi wskaźnikami, ale nie objaśnia wyznaczonej struktury zbioru danych. Analiza składników głównych pokazuje, że 3 czynniki wpływają na obserwowany poziom zanieczyszczenia atmosfery: gleba (pył mineralny) oraz źródła przemysłowe i transport. Wyznaczono różnice w udziale tych 3 czynników na terenie miejskim oraz wiejskim.