The control of diatom and cyanobacterial blooms in reservoirs using barley straw

A potable supply reservoir, with a long history of diatom blooms in spring and cyanobacterial blooms in summer, was treated with barley straw in March 1993 with subsequent additions in December 1993 and June 1994. Within two months of the initial treatment, algal numbers started to fall compared with previous years and have remained consistently lower throughout 1993 and 1994. Cyanobacteria have not bloomed and cell numbers remained low. Chemical analysis of the water showed locally elevated concentrations of geosmin close to the straw on one occasion but the overall concentration of this and a range of other organic molecules remained within acceptable limits and at concentrations similar to those found in other untreated reservoirs in the region. Observed and potential advantages to public health and potable supply management resulting from the use of barley straw are discussed.