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Total and Dissolved Metals in the Industrial Wastewater: a Case Study from Dhaka Metropolitan, Bangladesh

Md. Saiful Islam
Professor
Department of Soil Science, Patuakhali Science and Technology University, Dumki, Patuakhali-8602, Bangladesh

Md. Shariful Islam
Professor
Department of Agricultural Chemistry, Patuakhali Science and Technology University, Dumki, Patuakhali-8602, Bangladesh

Habibullah-AL-Mamun
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh

Shah Md. Asraful Islam
Associate Professor
Department of Plant Pathology, Patuakhali Science and Technology University

Dennis Wayne Eaton
Contract Faculty, Rutgers University, NJ, USA

Abstract/ Executive Summary:

The present study was conducted to assess the contamination of heavy metals in the industrial wastewaters collected from Dhaka city, Bangladesh. Seven different types of industries have been considered as the major sources of untreated effluents. Total and dissolved metals were analyzed using inductively coupled plasma mass spectrometer and compared with different international standard values. In samples, the ranges of Cr, Ni, Cu, As, Cd and Pb were 1.1–7910, 0.11–11, 0.69–13, 0.88–16, 0.01–9.3 and 0.19–11 mg/L and 0.76–1994, 0.04–5.2, 0.47–6.4, 0.26–5.7, 0.01–3.7 and 0.06–4.5 mg/L, respectively for total and dissolved concentration. The study revealed that the untreated activities of tanneries, dye-chemical, metal processing and battery manufacturing industries are contributing to the metal contamination in the surrounding environment. The concentration of heavy metals exceeded the acceptable environmental quality standards due to continuous discharge of untreated wastewaters that pose severe threat to the aquatic environment and human health in the urban area of Dhaka City. Results showed that rice husk can be fruitfully used for the removal of heavy metals from industrial wastewater. All possible sources of agro-based inexpensive adsorbents should be explored and their feasibility for the removal of heavy metals should be studied in detail.

Keywords: Industries, Wastewater, Heavy metals, Rice husk, Dhaka city, Bangladesh

Location: Department of Soil Science, Patuakhali Science and Technology University, Dumki, Patuakhali-8602, Bangladesh and Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa240-8501, Japan

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Heavy metal

Objectives:

To evaluate the concentrations level of trace metals in the wastewater samples collected from different industries and to assess the contamination levels as compared to international standards.

Methodology:

Sampling and pre-treatment Sampling stations were selected by site survey during August and September, 2013. Fifty seven wastewater samples were collected from the disposal channels of seven different types of industries such as tanneries, dye chemicals, textiles, metal processing, battery manufacturing, paper mills and jute mills in Dhaka City, Bangladesh. Wastewater samples were filtered immediately after collection using ADVANTEC® 0.45 µm size sterile syringe filter for estimation of dissolved metals and were transferred immediately into acid cleaned 100 mL polypropylene bottles. After filtration samples were preserved in the refrigerator until other chemical analysis was carried out. The physicochemical parameters such as pH, electrical conductivity (EC), suspended solid (SS), dissolved solid (DS), total solid (TS) and ash were estimated within the same day of sampling. Analytical grade reagents and Milli-Q water was used for solution preparation. For metal analysis, 20 mL of wastewater sample was treated with 1.5 mL 69% HNO₃and 4.5 mL concentrated HCl in a closed Teflon vessel and was digested in a Microwave Digestion System. The digested sediment and waste water samples were then transferred into a Teflon beaker and total volume was made up to 50 mL with Milli-Q water. The digested solution was then filtered by using syringe filter (pore size = 0.45 µm) and stored in 50 mL polypropylene tubes. Finally, blank digestion with 5 mL HNO₃ following the said digestion procedures were carried out to clean up the digestion vessels. Batch experiment Adsorption batch experiments were carried out by shaking a series of bottles containing various amounts of rice husk and heavy metal ions at normal pH condition. The pH of the slurry was adjusted to a desired value 6.5 and was agitated (agitation rate 200 rpm) in a shaking bath at (28 ±3°C) for 20 min until the pH was stabilized. Then, the Cr, Ni, Cu, A, Cd and Pb ions in the form of chromium chloride, nickel chloride, copper chloride, arsenic chloride, cadmium chloride and lead chloride were added to the bottles to make initial concentrations of 5–30 mg/L and the bottles were further agitated for 2 h until equilibrium was obtained. The residual concentration of heavy metals was determined by Inductively Coupled Plasma mass spectrometer (ICP-MS). Instrumental analysis and quality assurance For metals, samples were analyzed by using Inductively Coupled Plasma mass spectrometer. Multi-element Standard XSTC-13 solutions was used to prepare calibration curve. The calibration curves with R2 > 0.999 were accepted for concentration calculation. Internal calibration standard solutions containing 1.0 mg/L of indium, yttrium, beryllium, tellurium, cobalt and thallium. Working standards were prepared daily in 5% (v/v) HNO₃ at 69% ultrapure grade and were used. Multielement solution 1.0 µg/L was used as tuning solution covering a wide range of masses of elements. A blank also carried out in the sequential extraction experiment. A run included blank and samples were analyzed in duplicate to eliminate any batch-specific error. Before starting the analysis sequence, relative standard deviation (RSD, <5%) was checked by using tuning solution.

Source of Information: Environmental Nanotechnology, Monitoring & Management, Volume: 5, Pages: 74–80

Article Link (Online Journal): http://dx.doi.org/10.1016/j.enmm.2016.04.001

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The indiscriminate disposal of industrial wastewater in landfills and water body is considered as a hazardous practice for waste management. Contamination of heavy metals was investigated in the wastewater collected from seven different types of industries in Dhaka City, Bangladesh. The chemical analysis showed that all the industrial wastewater had high concentrations of suspended solids and dissolved solids. Total and dissolved concentrations of heavy metals in wastewater varied widely among the industries where tannery, dye-chemical, metal processing and battery manufacturing industries exceeded the permissible limits for industrial effluents, indicating high risk to the surrounding ecosystems. The results showed that rice husk was effective for the removal of heavy metals especially As, Cd and Pb from industrial wastewater. In this study rice husk was used as a case study for the removal of heavy metals with definite pH, contact time, agitation rate and temperature.

Knowledge Management: Journal