This research was conducted at the Central Laboratory of 350-bed capacity Keçiören Training and Research Hospital (Ankara, Turkey). Patients and samples are assessed via advanced technological applications in the hospital under Pathology, Radiology, Biochemistry, and Microbiology branches. A monthly average of 200 thousand biochemical and serological tests, and 20 thousand culture and manual tests are conducted at the central laboratory of the hospital. Based on an average 8-hour operation time, the devices used in the clinical laboratory of the hospital produce 561.06 liters of wastewater daily (Table 1). During the laboratory analyses, concentrated reagents are averagely diluted 20 to 1000 times subsequent to measurement and washout processes. Total serum is diluted to 10.000 times and a patient sample is diluted to 1.000.000 to 2.000.000 times. Therefore the wastewater amount reaches to substantial levels depending on the devices. According to the differences in the number of patients, the hospitals create an average of 500 to 1000 liters wastewater daily.

Wastewater from laboratory environment is collected in a storage tank via closed loop collection line. The wastewater is discharged to sewage system after disinfection and neutralization process. In the scope of the experimental studies, wastewater samples were collected from the storage tank as 24-hour composite samples. Monthly sample collection continued for 6 months. The samples were carried to the laboratory in storage boxes, which comply with the Standard Methods [15] and appropriate conservation criteria (cooler storage boxes, acidification, etc.) [16] .

Cadmium (Cd), lead (Pb), zinc (Zn), copper (Cu), chromium (Cr), cobalt (Co), nickel (Ni), aluminum (Al), and manganese (Mn) analyses were made in the scope of the study. Samples collected for heavy metal analyses were placed in polyethylene vials and the medium was acidified by adding 1% HNHNO₃. The biological activity of organisms and bacteria was thus terminated in order to transformation into forms other than metals. Samples were kept in fridge at −80˚C [17] . Upon collection of all the samples, analyses were made at the same time. Analyses took place in the same series of study in order to avoid intra- and inter-day variation.

Agilent 7500 CXICP-MS device was used in metal analyses of water samples and the analyses were conducted according to the Standard Methods [15] . 99.99% pure Argon gas was used for ionization of metals. Standard solutions at different concentrations of heavy metals were first prepared and measured at ICP-MS and the heavy metal concentrations in the samples were expressed in mg/L levels. Detector calibration was made by replicate and wave length calibration was made by 1 mg/L Li, Ce, Y, Tl (Merck) adjustment solutions before commencing analyses at ICP device. Upon calibration, a method was developed by entering the names of elements to be analyzed, appropriate wavelengths for the selected element, standard calibration solution concentrations and numbers, and the number of samples in the ICP program. Analyses were conducted after replicate, standard calibration solutions, and samples were placed in the tubes in the automatic sampler. Certified standard solutions of analytical purity were used as standard calibration solutions. Device operation standard solutions were prepared by 5, 10, 15, 20, 25 mg/L concentrations of 1000 ppm arsenic (As), mercury (Hg), and zinc (Zn) stock standard solutions. HNO₃ added to have 65% concentration. The replicate sample was also prepared by adding HNO₃ of 65% concentration to double distilled water. Separate calibration graphs were produced for each element by the use of a minimum of 5 standards and absorbance for standards were plotted in the graph against the standard concentration.

In order to determine the quantity of total bacteria in the collected water samples, 6 series of dilutions were prepared; upon which 1 ml from each sample were inoculated in agar with 5% sheep blood. The agar plates were incubated in aerobic environment for 24 to 48 hours at 37˚C. Furthermore, selective media were also inoculated besides agar with 5% sheep blood for determination of bacterial variety. For the purpose thereof, following inoculations, with the use of quantitative method, were conducted: Eosin Methylene Blue for determination of enteric bacteria, Bile Esculin Azide Agar with 100 mg/ml Azide for enterococci, Hektoen Enteric Agar and Chromogenic Salmonella plus Agar for Salmonella spp.-Shigella spp., Sabouraud Dextrose Agar for possible fungi growth, Specific Chromogenic Pseudomanas Agar for Pseudomonas spp., and finally Chromogenic E. coli Agar for E. coli. The inoculated media were incubated in aerobic environment for 24 to 48 hours at 37˚C. The media were inspected at 24th and 48th hours of incubation [17] [18] .

Bacterial suspensions were prepared in sterile tubes upon collection of preliminary information about bacteria through Gram Staining, Catalase Test for Gram positive bacteria and Oxidase Test for Gram Negative bacteria. The turbidity degree of suspensions were set to Mac Farland standard 0.5 by means of DensiCheck (BioMerieux) and advance identification processes were held using Vitec 2 GP card for Gram positive bacteria, and Vitec 2 GN card for Gram negative bacteria at Vitec 2 Compact (Biomerieux) automated system. The bacteria were identified in terms of types and species [17] [18] .

Antigen and Antibody determination: HbsAg, Anti-HCV, Anti-HIV, Toxoplasma IgM, Rubella IgM AND CMV IgM concentration was measured with automatic diagnostic system (Architect system, Abbott Diagnostics, U.S.A). The Architect system HbsAg, Anti-HCV, Anti-HIV, Toxoplasma IgM, Rubella IgM, CMV IgM assays, uses chemiluminescent immunoassay (CLIA) technology for the quantitative determination of hepatitis B surface antigen and antibody, hepatitis C antibody, HIV p24 antigen and HIV-1 and HIV-2 antibody, Toxoplasma gondii against formed IgM antibody, Rubella virus IgM antibody, CMV IgM antibody.

The findings of the physiochemical and heavy metal analyses for determining the characterization of hospital clinical laboratory wastewater were provided in Table 2. Wastewater pH values varied between 7.9 and 9.4 during the 6-month observation period. Hospital wastewater is generally alkaline. Nevertheless, intensive use of disinfectants may be associated with a change in pH value between different ranges. Therefore, different levels of pH change in hospital wastewater have been observed in different studies: 6.2 - 7.1 [19] , 5.1 - 10.4 [20] , and 7 - 8 [21] . The present study on clinical laboratory wastewater also observed alkaline nature of the wastewater.

It was reported that hospital wastewater had generally similar characteristics with domestic wastewater as regards BOD, COD, and SS concentrations [7] [19] [22] . The findings of the present study suggested that COD/ BOD ratio might vary between 2 to 3. This study observed that average BOD and COD values for a six-month period were 75.3 mg/L, and 934.2 mg/L respectively. As a result, it was seen that COD/BOD ratio could reach to a range of 10 to 12 in hospital clinical laboratory wastewater (Table 2). This suggested that mostly the laboratories accounted for the amount of chemically oxidizable organic matter in the hospital wastewater.TSS value varied between 98 - 162 mg/L ranges in the hospital laboratory wastewater (Table 2). Other studies reported higher values for TSS in hospital wastewater: 155 - 298 mg/L [13] , 539 mg/L [7] , and 72-243 mg/L [23] . The present study on laboratory clinical wastewater found that Cl and phosphate amounts in the wastewater were in the range of 129 - 156 mmol/L, and 15 - 30 mg/L respectively. It was suggested that Cl and phosphate might be originated from the kits used in devices and patient serums. Studies on hospital wastewater reported that Cl value might reach to higher concentrations between the ranges of 63.4 - 359.2 mg/L, especially due to the disinfectants [13] .

Cadmium (Cd), lead (Pb), zinc (Zn), copper (Cu), chromium (Cr), cobalt (Co), nickel (Ni), aluminum (Al), and manganese (Mn) in the hospital laboratory wastewater were measured for a six-month period in the scope of the study. Heavy metal concentrations based on analyses on monthly collected samples were provided in Table 3. Upon observation of the laboratory wastewater, copper had the highest concentration. Cu values varied between 0.44 and 0.85 mg/L, where the average Al, Cr, Cd, and Zn values were measured as 0.06, 0.07, 0.02,and 0.07 mg/Lin six-month period, and Mn, Co, Ni, and Zn values were <0.01.

Limit values that must be met by wastewater to be discharged to sewage system were determined pursuant to the Regulation of Wastewater Discharge into Sewage System in force in Turkey and Table 25 of the Regulation on Prevention of Water Pollution (Wastewater Standards Required for Discharge of Wastewater in Wastewater Infrastructure Facilities) [24] . In the scope of the aforementioned regulations the Pb, Cd, Zn, Cu, Ni, and Cr concentrations were within the limits required for direct discharge. However, those regulations did not provide a standard value for Co, Mn, and Al.

World Health Organization (WHO) [25] , Turkish Standards Institution (TSE 266) [26] , and USA Environmental Protection Agency (EPA) [27] provided the limit values of heavy metals in wastewater as regards human health. A comparison between the said standard values and the findings of our measurements based on the hospital clinical laboratory wastewater was provided in Table 4. The analysis results suggested that average Cd, Cr, and Pb concentrations were slightly above the standard values.

Principally the chemical and analysis kits accounted for the heavy metal concentrations in the wastewater of hospital clinical laboratories. Several studies on hospital wastewater reported such heavy metals as Pb, Hg, Pt, Cd, and Sr in the wastewater [1] [4] [28] . Studies from the relevant literature included wastewater quality analyses for the totality of the hospital wastewater. The first ever investigation as regards the heavy metal concentrations in hospital clinical laboratory wastewater was conducted in the present study and it was found that the heavy metal levels could still pose a health risk although they were within the limits for discharge into sewage system.

Bacterial isolation and count were conducted in the samples collected for the purpose of the study for Pseudomonas aeruginosa, Escherichia coli, Acinetobaumanii, CNS (Coagulase-negative staphylococcus) and the results were provided in Table 5. Certain levels of pathogen and antibiotic resistant bacteria were found in the samples. During the experimental studies, it was found that Pseudomonas aeruginosa, Acinetobaumanii, and Coagulase- negative staphylococcus had populations of 2 × 10⁴ - 9 × 10⁶ cfu/ml, 5 × 10⁴ - 6 × 10⁶ cfu/ml, and 7 × 10¹ - 5 × 10² cfu/mL respectively. These pathogen organisms may pose important risk to human health. These organisms were also reported in studies on hospital wastewater [13] [22] [29] .

E. coli levels varied between 9 × 10² and 8 × 10⁴ cfu/ml ranges in clinical laboratory wastewater samples. The change in bacteria levels during the six-month period was as a result of the difference in patient serum numbers. Different studies reported total coliform numbers in hospital wastewater as 10⁶ (colony/100ml) [1] , 1 × 10⁸ (colony/L) [30] , 1 - 2.5 × 10⁴ (PFU/100ml) [31] , 1.2 - 3.3 × 10³ (MPN/100ml) [22] . The values vary by such factors as number of patients and hospital capacity [32] .

Antigen and antibody analyses were made for the wastewater samples. Distribution of antigens and antibodies by month was provided in Table 6. Three wastewater samples were positive for Hepatitis B antigen. Positive IgM antibody results suggested that the person in question had recent contact with the pathogen. Therefore, despite the fact that viral pathogens were not directly included in the study, the occurrence of IgM antibodies in the wastewater might be associated with the occurrence of the pathogen in the wastewater as well.

+Reactive, −Nonreactive.