Influence of seasonal variation in water quality on the microalgal diversity of sewage wastewater

An investigation was undertaken to assess the variation in microalgal diversity vis a vis physicochemical characteristics of sewage wastewater at monthly time intervals. Diversity analyses revealed the presence of algal members belonging to all major divisions, with a predominance of Cyanophyta. Shannon-Wiener and Simpson's diversity indices illustrated low microalgal diversity in sewage wastewater. Highest chemical oxygen demand (COD) of 14,000 mg L-1 was recorded in December 2012. Spectrometric analyses of sewage wastewater revealed the presence of heavy metals, with Cr ranging from 3 to 4 mg L-1 being detected in all the samples collected over the year. A positive correlation was found between COD and total heavy metal concentration (r = 0.77). The indices of microalgal diversity showed a positive correlation with nutrients and a negative correlation with COD and heavy metal concentrations, implying the significant role of these factors in influencing the algal population. Phormidium sp. was the dominant genus present throughout the year. (C) 2013 SAAB. Published by Elsevier B.V. All rights reserved.