Abstract: A process for treating wastewater through the use of powdered natural ligno-cellulosic materials (PNLM) for (a) physically removing colloidal and suspended volatile solids through adsorption and enhanced floc-formation and settling during pretreatment; (b) adsorbing toxic substances and elements that interfere with biological processes, thus serving to reduce their contact with and exposure to activated sludge organisms effecting wastewater treatment functions; (c) providing fixed surfaces in activated sludge wastewater treatment bioreactors for bacteria and other organisms favoring attached growth in circumstances devoid of such surfaces; (d) reducing production of biological sludge, while also helping to maintain high treatment efficiencies; and (e) following aeration, enhancing the settling characteristics of sludge with respect both to speed of settling and the vertical profile of the settled sludge.