Actually, ground water is free from pathogenic bacteria (which cause diseases). it does not involve the suspended particles, which make the water turbid, unlike surface water of river or stream which contain a lot of particles in it. Ground Water requires nearly no treatment for its usage. while surface water requires many process like sedimentation, filtration, disinfection etc. ground water are usually hard i.e it contains in it calcium ions (and some other Di and Tri valent inos which cause hardness of water) hence ground water provide us an small beneficial amount of calcium. but this water is not good for boilers of industries as this may form a calcium layer(called as scaling) within the boiler and it may burst. although gronud water is good but it may contain a lot of dissolved solids and metals in it (usually in industrial areas) which may be harmful.