Evaluation of 3-D spatial distribution of dissolved oxygen concentrations in a eutrophic lake.

In this study, three-dimensional (3-D) ordinary kriging of dissolved oxygen (DO) concentrations was performed for a eutrophic reservoir based on 81 sampling points using Stanford Geostatistical Modeling Software (SGeMs). Potential hotspots (problematic zones in terms of water quality with high/low DO concentrations) not only at the surface but also in deeper layers of Porsuk Dam Reservoir (PDR) were evaluated. Moreover, 3-D distributions of DO, and specific conductivity (SC) were examined against the thermocline layer identified using the 3-D temperature data. Thermocline layer existed between 10 and 14 m below the surface based on 3-D temperature data. This result showed that the traditional approach of collecting samples from mid-depths may cause incomplete characterization and evaluation of water quality as thermocline layer may not coincide with mid-depth. Although the variation in SC values and temperatures above and below the thermocline layer were relatively homogeneous, this was not the case for DO. 3-D DO distribution suggested a better location for water withdrawal for domestic purposes. 3-D DO maps generated by predicting data at unmeasured locations at different depths could be used as input for 3-D water quality estimation in the reservoir through model simulations in future. Moreover, the outcomes can also be useful in the segmentation (physical configuration) of the water body for future water quality modeling studies.

Plant-wide modeling of a metropolitan wastewater treatment plant to reduce energy consumption and carbon footprint.

A real metropolitan wastewater treatment plant (RWWTP) serving a population equivalent of 1.55 million was modeled to reduce energy consumption and carbon footprint (CFP). An approach was proposed to handle the dilution factor and partial aeration due to discontinuous air diffuser locations in the Bardenpho-5 configuration. Various operational, structural, and configurational modifications were evaluated. Results indicated that management scenarios might provide conflicting outcomes for different targets. Reduced energy consumption may not result in lower CFP at the same time. Moreover, operational changes that would impact total nitrogen (TN) concentrations and N2O release may significantly impact CFP. A policy of using a modified Bardenpho-5 process with reduced internal recycle (IR) ratio, waste activated sludge (WAS), and return activated sludge (RAS) flow rates provided the lowest CPF. Modified Bardenpho-5 process and replacing belt thickeners with gravity thickeners supplied the highest savings in energy consumption. Overall, up to 14% and 20% reductions were possible in the energy consumption and CFP of the plant, respectively. The RWWTP may save up to 10% in energy expenses annually by operational modifications.

Comprehensive analysis and modeling of landfill leachate.

Landfill leachate data compiled from 220 different landfills from 46 countries in Europe, Middle East, Asia, Africa, and America was analysed by multivariate statistical approaches. Data pre-treatment procedure such as handling of outliers, completion of missing data, and standardization of data was applied to prepare the raw data matrix for the complex statistical analyses including cluster and principal component analyses (PCA). Regression modeling was conducted to estimate leachate parameter values. Results show that usually inorganic parameters, if included in the PCA, dominated the first components indicating the highest correlations as well as accounting for majority of the variation in the data. Those highly correlated parameters in landfill leachate could be important in evaluation of their pathways into leachate in terms of transport and biodegradation mechanisms as well as their elimination potential from sampling and analytical procedures during monitoring activities at landfills. Some leachate parameters having significantly high concentrations, such as organics, salts, and some inorganics, impacted the formation of components in PCA. This in turn provides important information about the specific characteristics of leachate samples and the landfills to which they belong.

Qualitative and quantitative assessment of waste generation in a refrigerator-manufacturing plant based on a waste tree and mass balance.

In this study, wastes originating at each production station during refrigerator manufacturing were identified and classified based on a waste tree. A mass balance study revealed a total waste production factor of 0.046 kg/kg of a product of which 75.3%, 23.9%, and 0.8% were non-hazardous wastes (NHWs), packaging wastes (PWs), and hazardous wastes (HWs), respectively. Wastes produced during refrigerator manufacturing were grouped under 35 different waste codes. Waste codes that contributed more than 5% by weight were 15 02 02 (contaminated absorbent material), 15 01 10 (contaminated packaging), 16 02 13 (electronic cards), 07 02 14 (polyol) and 08 05 01 (isocyanates), 19 08 13 (treatment sludge), 16 02 15 (capacitors), and 13 01 13 (hydraulic oil) for HWs, 12 01 01 (ferrous metal), and 16 02 16 (components) for NHWs, and, finally, 15 01 03 (wooden), 15 01 01 (paper&cardboard), and 15 01 02 (plastic) for PWs over 5 years. Scrap costs were used as a surrogate to determine production stages that generated high amounts of metal and plastic wastes. Logarithmically, increasing and decreasing trends were observed for PWs and NHWs over the study period, respectively. HW amounts did not exhibit a statistically significant trend. Twenty-eight BATs (best available techniques) were identified that could be applied in refrigerator manufacturing for waste minimization and management. Among those, 8 of them were proposed for further improvement for waste management in the facility.

Development of a fate and transport model for biodegradation of PBDE congeners in sediments.

Polybrominated diphenyl ethers (PBDEs) are a family where each congener possesses different physicochemical properties, persistence and/or toxicity. Biodegradation can selectively change the abundance of congeners. These warrant modeling of individual congeners by considering biodegradation pathways together with fate and transport (F&T) mechanisms. Accordingly, this study aims to develop a F&T model (Fate and Transport model for Hydrophobic Pollutants - FTHP) that integrates congener specific biodegradation of PBDEs in sediments. The model is tested using sediment data from a location representing the Lower South Bay of San Francisco. Results demonstrated settling, resuspension, and biodegradation as important mechanisms. FTHP is then used to predict congener concentrations in a period of 20 years for two cases (constant and time-dependent water column concentrations) and four alternative scenarios: no intervention (i.e., natural attenuation, also serves as the base case), no degradation, dredging and biostimulation. The greatest impact on the reduction of total PBDE concentrations was achieved by a reduction in water column concentrations, i.e. source control, and dredging. On the other hand, biostimulation coupled with source control was the most effective in reducing bioaccumulative PBDE congener concentrations and almost as effective as dredging for the rest of congeners. Proposed FTHP model can distinguish between congeners and help devise informed management plans which focus on decreasing risks associated with persistent and bioaccumulative compounds in contaminated sediments.

Effects of anaerobic digestion enhanced by ultrasound pretreatment on the fuel properties of municipal sludge.

In this study, effects of ultrasound pretreatment on combustion characteristics and elemental composition of municipal sludge were examined for energy-based evaluation of sludge pretreatment. Waste activated sludge (WAS) from a municipal wastewater treatment plant was pretreated with ultrasound at varying durations and was subjected to anaerobic digestion in a biochemical methane potential (BMP) assay. Changes in gas production rates, calorific value (CV), elemental compositions, and ash contents of sludge samples were examined to assess the effects of pretreatment and digestion. Sonication at 0.73 W/mL enhanced gas production by 28%. Moreover, volatile solids (VS) and chemical oxygen demand (COD) removals increased from 41 to 45% and 33 to 37%, respectively. Following anaerobic digestion, CVs of samples decreased by about 18%. Sonicated samples exhibited a higher decrease. In order to quantify the change in overall energy content, total solids (TS) reduction was also taken into account. Loss was magnified as both CV and the amount of TS that would provide the overall energy were reduced. This loss was 38% for the control group and 41% for the 15 min sonicated sludge. Digestion decreased the C content of sludge by about 20% and H content by 50% due to biogas production. Ash content increased relatively as some of the combustible solids were lost due to digestion. Experimental results indicate that if sludge is to be combusted, digestion with or without ultrasound pretreatment may be disadvantageous if the aim is to maximize energy gain from sludge.

Evaluation of solar sludge drying alternatives by costs and area requirements.

Thermal drying is a common method to reach above 90% dry solids content (DS) in sludge. However, thermal drying requires high amount of energy and can be expensive. A greenhouse solar dryer (GSD) can be a cost-effective substitute if the drying performance, which is typically 70% DS, can be increased by additional heat. In this study feasibility of GSD supported with solar panels is evaluated as an alternative to thermal dryers to reach 90% DS. Evaluations are based on capital and O&M costs as well as area requirements for 37 wastewater treatment plants (WWTPs) with various sludge production rates. Costs for the supported GSD system are compared to that of conventional and co-generation thermal dryers. To calculate the optimal costs associated with the drying system, an optimization model was developed in which area limitation was a constraint. Results showed that total cost was minimum when the DS in the GSD (DS(m,i)) was equal to the maximum attainable value (70% DS). On average, 58% of the total cost and 38% of total required area were associated with the GSD. Variations in costs for 37 WWTPs were due to differences in initial DS (DS(i,i)) and sludge production rates, indicating the importance of dewatering to lower drying costs. For large plants, GSD supported with solar panels provided savings in total costs especially in long term when compared to conventional and co-generation thermal dryers.

An evaluation of potential sampling locations in a reservoir with emphasis on conserved spatial correlation structure.

In this study, kernel density estimation (KDE) was coupled with ordinary two-dimensional kriging (OK) to reduce the number of sampling locations in measurement and kriging of dissolved oxygen (DO) concentrations in Porsuk Dam Reservoir (PDR). Conservation of the spatial correlation structure in the DO distribution was a target. KDE was used as a tool to aid in identification of the sampling locations that would be removed from the sampling network in order to decrease the total number of samples. Accordingly, several networks were generated in which sampling locations were reduced from 65 to 10 in increments of 4 or 5 points at a time based on kernel density maps. DO variograms were constructed, and DO values in PDR were kriged. Performance of the networks in DO estimations were evaluated through various error metrics, standard error maps (SEM), and whether the spatial correlation structure was conserved or not. Results indicated that smaller number of sampling points resulted in loss of information in regard to spatial correlation structure in DO. The minimum representative sampling points for PDR was 35. Efficacy of the sampling location selection method was tested against the networks generated by experts. It was shown that the evaluation approach proposed in this study provided a better sampling network design in which the spatial correlation structure of DO was sustained for kriging.

A fuzzy rule based remedial priority ranking system for contaminated sites.

Contaminated site remediation is generally difficult, time consuming, and expensive. As a result ranking may aid in efficient allocation of resources. In order to rank the priorities of contaminated sites, input parameters relevant to contaminant fate and transport, and exposure assessment should be as accurate as possible. Yet, in most cases these parameters are vague or not precise. Most of the current remediation priority ranking methodologies overlook the vagueness in parameter values or do not go beyond assigning a contaminated site to a risk class. The main objective of this study is to develop an alternative remedial priority ranking system (RPRS) for contaminated sites in which vagueness in parameter values is considered. RPRS aims to evaluate potential human health risks due to contamination using sufficiently comprehensive and readily available parameters in describing the fate and transport of contaminants in air, soil, and groundwater. Vagueness in parameter values is considered by means of fuzzy set theory. A fuzzy expert system is proposed for the evaluation of contaminated sites and a software (ConSiteRPRS) is developed in Microsoft Office Excel 2007 platform. Rankings are employed for hypothetical and real sites. Results show that RPRS is successful in distinguishing between the higher and lower risk cases.

Possible transmission risks and genotype distribution of hepatitis C virus infection in Western Turkey.

BACKGROUND/AIMS: The aim of this study was to investigate the risk factors which may be involved in the transmission of hepatitis C virus and to determine the recent distribution of various genotypes in Western Turkey. MATERIALS AND METHODS: The risk determination study consisted of 215 patients whose serum samples were sent to the Medical Microbiology Laboratory at Ege University Hospital between 2005 and 2010 and were anti-hepatitis C virus positive. For the determination of recent genotype distribution, genotyping results of all 535 patients sent to the same laboratory from 2007 to 2011 were analyzed. Information on possible risk factors for the transmission of hepatitis C virus was obtained by a telephone questionnaire. Hepatitis C virus typing was performed by restriction fragment length polymorphism analysis. RESULTS: The most frequently reported risk factors were history of dental procedures in 171 (79,5%) patients and surgical operations in 137 (63,7%) patients. Genotype 1 was observed in 499 of the 535 patients (93,3%) with chronic hepatitis C virus infection. Of these, 69 patients showed infection with subtype 1a (12.9.%) and 430 - with subtype 1b (80.4%). Genotype 3 was determined in 20 patients (3,7%), genotype 2 - in 8 patients (1,5), and genotype 4 - in 8 patients (1,5%). CONCLUSIONS: Even though there is an increase in non-1 genotypes, Turkish patients with chronic hepatitis C still represent a rather homogenous group with genotypic diversity encountered rarely. The risk factors detected in the patients admitted to our hospital are mainly medical procedures which can be prevented by the use of simple infection control practices and implementation of an education program.

Application of spatial and non-spatial data analysis in determination of the factors that impact municipal solid waste generation rates in Turkey.

In studies focusing on the factors that impact solid waste generation habits and rates, the potential spatial dependency in solid waste generation data is not considered in relating the waste generation rates to its determinants. In this study, spatial dependency is taken into account in determination of the significant socio-economic and climatic factors that may be of importance for the municipal solid waste (MSW) generation rates in different provinces of Turkey. Simultaneous spatial autoregression (SAR) and geographically weighted regression (GWR) models are used for the spatial data analyses. Similar to ordinary least squares regression (OLSR), regression coefficients are global in SAR model. In other words, the effect of a given independent variable on a dependent variable is valid for the whole country. Unlike OLSR or SAR, GWR reveals the local impact of a given factor (or independent variable) on the waste generation rates of different provinces. Results show that provinces within closer neighborhoods have similar MSW generation rates. On the other hand, this spatial autocorrelation is not very high for the exploratory variables considered in the study. OLSR and SAR models have similar regression coefficients. GWR is useful to indicate the local determinants of MSW generation rates. GWR model can be utilized to plan waste management activities at local scale including waste minimization, collection, treatment, and disposal. At global scale, the MSW generation rates in Turkey are significantly related to unemployment rate and asphalt-paved roads ratio. Yet, significances of these variables may diminish at local scale for some provinces. At local scale, different factors may be important in affecting MSW generation rates.

Challenges in development and implementation of health-risk-based soil quality guidelines: Turkey's experience.

Management of contaminated sites is a critical environmental issue around the world due to the human health risk involved for many sites and scarcity of funding. Moreover, clean-up costs of all contaminated sites to their background levels with existing engineering technologies may be financially infeasible and demand extended periods of operation time. Given these constraints, to achieve optimal utilization of available funds and prioritization of contaminated sites that need immediate attention, health-risk-based soil quality guidelines should be preferred over the traditional soil quality standards. For these reasons, traditional soil quality standards are being replaced by health-risk-based ones in many countries and in Turkey as well. The need for health-risk-based guidelines is clear, but developing these guidelines and implementation of them in contaminated site management is not a straightforward process. The goal of this study is to highlight the problems that are encountered at various stages of the development process of risk-based soil quality guidelines for Turkey and how they are dealt with. Utilization of different definitions and methodologies at different countries, existence of inconsistent risk assessment tools, difficulties in accessing relevant documents and reports, and lack of specific data required for Turkey are among these problems. We believe that Turkey's experience may help other countries that are planning to develop health-risk-based guidelines achieve their goals in a more efficient manner.

[Evaluation of immunoblot-based assay for detecting Epstein-Barr virus viral capsid antibodies]. / Epstein-Barr virus viral kapsid antikorlarinin saptanmasinda immünoblot yönteminin degerlendirilmesi.

Various attempts have been made to improve Epstein-Barr virus (EBV) serodiagnosis by developing more practical and objective methods than immunofluorescence-based assays. In the present study, the performance of immunoblot-based assays were evaluated by comparing the results obtained by the gold standard immunofluorescence antibody (IFA) test for the detection of IgM and IgG antibodies against EBV viral capsid antigen (anti-VCA). Serum samples of 277 patients admitted to Ege University Hospital for routine EBV diagnosis were included in the study. The age range of the patients was 3 months-89 years (mean 28 years) and 104 of them were females and 173 were males. All the samples were assayed by commercial immunoblot (Euroline IgM and IgG; Euroimmun, Germany) and IFA (EBV-CA IgG and IgM, Euroimmun, Germany) methods. Crosstabulation, chi-square test and phi (phi) measures in SPSS 16.0 statistical package programme were used for data analysis. Of the 216 samples that were interpreted as positive with immunoblot-based IgM assay, only 34 (15.7%) were confirmed as positive with IFA, whereas 162 (75%) were negative, and 20 (9.3%) were equivocal (phi = 0.167; low correlation). Of the 85 samples that were anti-VCA IgG positive with immunoblot assay, 82 (96.5%) were positive, 2 (2.3%) were negative and 1 (1.2%) were equivocal with IFA (phi = 0.441; significant correlation). When the indeterminate results obtained by IFA test were excluded from the evaluation, the correlation between immunoblot VCA IgG and IFA IgG was 85.4% (88/103) and between immunoblot VCA IgM and IFA IgM was 27.3% (69/253). When the intensities of bands were evaluated for IgM testing, it was noted that as the intensity of the bands increased (1+ to 3+), IFA VCA IgM reactivity rates increased (from 9.9% to 29.5% for p19 band; from 24% to 85.7% for gp125 band). For immunoblot VCA IgM testing, 165 samples were found to be positive only for VCA p19 band. Of these samples, 135 (81.8%) were negative, 15 (9.1%) were positive and 15 (9.1%) were equivocal with IFA. It is observed that even though immunoblot assays with automated blotting and scanning systems can be a convenient alternative to immunofluorescence assay, the rate of false positivity obtained for VCA IgM was high (75%). It was concluded that in laboratories which apply immunoblotting as a primary screening test for EBV serodiagnosis, the positive VCA IgM results (particularly isolated p19 band positivity) and the presence of low intensity bands, should be confirmed by IFA testing.