Industrial wastewater (effluents), nearby soil and relevant groundwater samples, collected from twelve industries in Hattar Industrial Estate (HIE), NWFP Pakistan, were analyzed and examined towards environmental status evaluation in terms of characterization and distribution of selected metals using standard analytical methods. The triplicate sampling was conducted during September 2002 to September 2004, and the selected metals included Na, K, Ca, Mg, Fe, Mn, Cr, Co, Cd, Ni, Pb and Zn for estimation in samples pertaining to the three media. In addition, physico-chemical parameters relevant to these samples were also estimated in the three media. The metals in samples were estimated by the Flame Atomic Absorption Spectroscopic (F AAS) method using automatic background compensation mode. The related physico-chemical parameters estimated were temperature, pH, conductivity, total dissolved solids (TDS), dissolved oxygen (DO), alkalinity, chemical oxygen demand (COD), chlorides, total hardness, sulfate, phosphate and nitrate, estimated by the standard APHA analytical procedures. The background and existing levels of metals in the effluent, soil and ground water samples were also determined and compared with counterpart international data, reported by world regulatory agencies, such as WHO and EPA, US. Metal-to-metal correlation and source identification was undertaken as an integral part of the present study through univariate and multivariate statistical analysis of the finished data. Basic descriptive statistical parameters, such as minimum, maximum, mean, standard deviation, kurtosis and skewness were evolved to furnish information on selected metal distribution while statistical correlations were handled to characterize interdependence of metal pairs and contributory pollutant sources. A thorough regression study was evolved towards predicting the concentration of effluent metal levels in terms of regression equations. The multivariate technique of Principal Component Analysis (PCA) was conducted to identify sources of metals interlinked in the three media.
According to the results obtained from the present study, the trace metal content of effluents from industries such as chemicals, textiles, paper/pulp, ,oil and ghee were found to be higher in concentration of Na, Cr, Co, Cd, Mn and Pb, far exceeding the maximum allowed safe limits. Some of the effluent samples from Pak Chromium and Hattar Chemicals exhibited elevated concentrations of Na and Cr that exceeded 500 mg L-l. The linear correlation analysis of the effluent matrix revealed that Fe and K, Mn and Co, and Cr and Cd were strongly correlated, with r-values at 0.778, 0.746, 0.566, respectively, evidencing significant mutual interdependence of these metal pairs. The study of soil, adjoining these industries showed more than 1000 fold increase in the average concentration of Cr evidencing gross pollution of soil. Increased level of these metal concentrations was observed for groundwater samples collected from the periphery of these industries, showing the percolation of pollution load into the groundwater through soil. The metal-to-metal linear correlation study and regression relationships supported the above facts. Furthermore, Pb, Fe, Co, Cd and Mn concentrations were also found well above the permissible limits in effluents from Pine Match and Wah Nobel industries with Cr concentration ranging between 7.930 and 37.80 mgL-1. Textile and paper industry effluents also showed enhanced concentrations of Na, Ca, Cr, Co, Ni and Pb, thus evidencing a probable degradation of the environmental quality of the local area including groundwater and soil. A parallel pattern of metal distribution was observed for the five oil and ghee industries located in the HIE. Cr concentration was again found at 0.424 mg L-1 followed by Ni, Zn and Pb at concentrations 0.338, 0.325 and 0.301 mgL-1, respectively. The effluent related Physico-chemical parameters such as pH, conductivity, TDS, DO, COD, BOD, total hardness, chlorides and sulfates were also found well above the maximum safe limits. The DO concentration observed in almost all effluent samples remained far below the minimum limit required for sustainable aquatic life.
Groundwater samples were also analyzed and found to be well above the safe limits set for drinking water quality by WHO. The Na and Ca contents, with an average of about 256.3 mg L-1 Na and 122.7 mg L-1 Ca were found in gross groundwater samples drawn from peripheral locations around the estate. Chromium in these water samples was found to range between 0.102-0.231 mg L-1, thus exceeding the upper safe limit for Cr laid down at 0.05 mg L-1 for safe drinking water
Trace metal analysis of water extracts of soil adjoining these industries were conducted in order to assess the impact of metal load from the effluents on nearby soil and ground water. The study showed increased levels of most of the metals up to 10-15 folds, compared with background soil levels, with the only exception of Zn and Ni. The pH values of some soil extracts in water were found to be highly acidic, indicating a direct adverse impact of the effluents on the local soil, expected to ultimately pollute local vegetation.
The overall distribution of metals in the effluents samples reflected a strong metal-to-metal correlation in groundwater and soil samples. The PCA identified different groups of metals based on their origins in the three media evidencing a clear picture for pollution source appointment. The screening and analysis of different groundwater samples collected from HIE further supported the fact that the discharged effluents were percolating through the soil bed directly into the groundwater table. This could be the causative of recorded trace metal levels and physico-chemical parameters that exceeded the allowed limits, rendering the ground water unfit for use, both for drinking and industrial purposes. The study thus brought forth the fact that the unregulated and untreated wastewater was a real cause of concern towards exceedingly high levels of metals and water quality parameters. The industrial effluents were noted for their potentiality of ultimately polluting the vegetation and seriously affecting the health of the local population in the area. The existing pollution situation calls for an effluent treatment facility in the HIE to control the ever increasing pollution load on the local environment. Currently, a constant monitoring program needs to be initiated to reform the present HIE into a safe industrial enterprise.