Complex sentence: The waste from the industries along the Irwell polluted the river so heavily that by the 1850 it was virtually devoid of wildlife, however, since the late 19th century many attempts have made to improve the quality of the water.
Split into simpler sentences: The waste from the industries along the Irwell polluted the river so heavily that by the 1850 it was virtually devoid of wildlife. However, since the late 19th century many attempts have made to improve the quality of the water.