Why is polluted ground water hard to clean?

Answer 1

Polluted groundwater is difficult to clean mainly because it is:

• Hard to monitor: Being underground the location of the pollutant is difficult to detect and measure. Underground water flows cannot be see or measured and variations in porosity of the soil or strata can have impacts that re not readily apparent.
  
• Hard to collect and treat: To remove groundwater it is necessary to create a 'cone of depression" in the water to draw the water and pollutants to a removal point. The porosity of the soil or other material makes the establishment of such collection difficult. The measures such as filtration or in situ chemical treatment are almost impossible. Stripping with air flows is only appropriate for volatile materials. Once collected the water must be treated by surface facilities. The treated water must then be returned to the aquifer or replaced with fresh clean water to preserve the water supply.
  

Answer 2

Water pollution is quite common and not difficult to measure or to prove. Visual (oil slicks, colours,and turbidity) and odour clues are often present , Biological examination (dead fish, benthic organism studies) can exstablsh as level of ecosystem impact. sSmple chemical methods ca quantify the concentrations and potential impacts.

Answer 3

you cant really extract it unless you have a ton of expensive equipment