Structural and Functional Changes in River Microbial Communities After Dairy Wastewater Discharge

ABSTRACT

The introduction of an integration approach for management of the water basins, including assessment and control of stream water quality and sediment quality, as well as regulation of the pollutant influx in the water receiver, is necessary. The changes in the microbial communities, as a response to the chronic discharge of untreated dairy wastewater, were followed in river and in depth, in three river components “stream water—sediment water—sediments”. The water quality of Leva River decreased after dairy wastewater discharge as the microbial communities reacted with structural and functional changes, related with enhancement of aerobic heterotrophs and the values of total dehydrogenase activity and phosphatase activity index. The result was a decrease of organic matter and nutrients in the stream water in Station 4. However, an improvement of river water quality was not ascertained according to the Bulgarian State Standard. The applied ecological theory for r/K- strategists showed that in the stream water the microbial community is presented with fast growing populations, while in the sediment water and sediments prevailed slow growing bacteria. In the sediments aerobic heterotrophs were with higher density and showed higher activities of total dehydrogenase, phosphatase and protease. The obtained results confirmed that microbial community in the sediment zone is an important factor for the regulation of the transformation processes of organic matter and nutrients in water and sediments, as well as for the formation of river water quality in water receiver.

Keywords:

• microbial community
• enzymological indicators
• river water quality
• sediments
• dairy wastewater