List of top Surface Environment Questions on Air, water and soil: Quality standards

The void ratio of an unconsolidated soil heap of volume 1000 m3 is 1.0. If the soil heap is consolidated to a volume of 800 m3, the corresponding void ratio is_____.(round off up to 2 decimals)
A 10 ml sample of wastewater is diluted with water having no BOD, to fill a 300 ml BOD bottle. The initial DO of the diluted waste water is 9.0 mg/l. If the BOD\(_5\) of the waste water sample is 60 mg/l, the final DO of the diluted waste water in mg/l, is