Total and dissolved metals in the industrial wastewater: A case study from Dhaka Metropolitan, Bangladesh

- Heavy metals were analysed from wastewater of different industries.
- Elevated metals were found for tannery, dye and metal processing industries.
- As, Cd and Pb were much higher than the environmental standard.
- Rice husk removed a considerable amount of metals from wastewater.

The present study was conducted to assess the contamination of heavy metals in the industrial waste waters 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 (ICP-MS) 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.