Abstract: In a processing for treating waste containing effluent water from a food processing plant, the effluent water is contacted with a flocculant comprising a crude algal composition or a crude alkali processed algal composition obtained from algae selected from the classes Rhodophyceae, Cyanophyceae, Chlorophyceae and Phaeophyceae, at an acidic pH. A floc, which contains substantially all of the solid waste components of the effluent water, is formed as a result of the treatment process, and can be recovered for use in animal feedstocks or as other products such as fertilizers, or safely disposed of an in landfill operations. The clarified effluent water is sufficiently waste free that it can be forwarded to a secondary treatment facility or back into the food processing plant for reuse in certain plant operations.