What are the cost and energy efficient technologies and solutions for industrial effluent treatment?

Industrial effluents constitute one of the largest categories of liquid pollution worldwide, with significant negative impacts on the health of nearby communities, ground water and surface water. With stricter environmental norms, diverse industries in most countries are now treating their effluents before discharge. But a good part of such effluent treatment either involves significant energy use or in turn needs chemical treatments. What are the sustainable solutions and avenues available for treating industrial effluents with lower energy and fewer chemicals?