Water quality assessment of East Kolkata Wetland with a special focus on bioremediation by nitrifying bacteria

Phytoplankton diversity in wastewater impacted Indian Ramsar site: a study from East Kolkata Wetland

A seasonal study was undertaken to understand the influence of wastewater on phytoplankton distribution in a water body of East Kolkata Wetland (EKW), a designated Ramsar site in Kolkata, West Bengal, India. A total of 19 different genera of phytoplankton belonging to 5 phyla were recorded. Among all the groups, Chlorophyceae was found to be dominated by 8 genera followed by Bacillariophycaeae (4 genera), Cyanophyceae (4 genera), Euglenophyceae (2 genera), and Zygnematophyceae (1 genus). Seasonal variability showed maximum dominance of phytoplankton during post-monsoon and least during pre-monsoon months. Shannon-Wiener diversity (H') indices indicated Bacillariophyceae to be most species rich (1.059) while the most dominant group (D) was observed to be Chlorophyceae (0.507). Assessment of Palmer algal pollution index (PI) revealed the water body is impacted by high organic pollution during monsoon (22) compared to the pre-monsoon (19) and post-monsoon seasons (15). The results of canonical correspondence analysis (CCA) indicated water temperature, alkalinity, total dissolved solids, dissolved oxygen, and electrical conductivity as the major influencing parameters for growth and distribution of the phytoplankton in the water body. Therefore, it can be stated that hydrological alteration of a water body fed with wastewater plays a significant role in regulating the plankton density, richness, and diversity.

Geochemistry and mass balance of selected heavy metals in East Kolkata Wetlands, a Ramsar site of West Bengal, India

A geochemical profile of the East Kolkata Wetlands and its efficiency in treating municipal and industrial wastewater is presented in this study. The mean concentration (mg/L) of some of the trace metals in the untreated pond waters decreased in the order of Mn (12.6) > Cr (11.8) > Fe (8.0) > Ni (6.2) > Zn (2.7) > Cu (2.6) > As (2.0) > Pb (1.8) > Cd (0.2). The corresponding mean concentration (mg/kg, dry weight) of the sediment trace metals decreases in the order of Fe (446.2) > Mn (114.1) > As (112.4) > Cr (30) > Zn (9.0) > Ni (6.8) >Cu (5.7) > Pb (3.0) > Cd (0.5). Our study found that the bioremediation of the wastewaters containing Al, Cr, Mn, Fe, Pb, Ni, Cu, and Zn was not uniform in all the ponds. Although reduced concentrations of Mn and Fe were found in 98% of the treated pond waters, 56% of the ponds could not remove Zn and As. Mass balance calculation showed that the differential load after microbial treatment of the wastewaters decreased in the order of Cr (differential load 3463 kg/day), Ni (1743 kg/day), Cu and Zn (681, 684 kg/day, respectively).