produces chlorinated byproducts1 with potential chronic health risks, including the trihalomethane (THM) group, has caused a major reassessment of water treatment practices in this country.5 Available technical options to meet proposed trihalomethane standards4 include (1) substituting new disinfectants for chlorine, (2) reducing the trihalomethane precursor concentration and altering the point of chlorine addition (elimination of prechlorination), and (3) removing trihalomethanes and other chlorinated compounds produced during treatment. Should chlorination be retained as a potable water treatment method, removal of the THM precursors prior to chlorine addition is an obvious treatment strategy now used by several water utilities' that is likely to be used more extensively in the future.

Modified Coagulation for Improved Removal of Trihalomethane Precursors

Comparison of chemical flocculation and dissolved air flotation of anaerobically treated palm oil mill effluent

Relevant information on the restoration of lakes is presented. The restoration procedures considered are applicable to the water, the bottom sediments, and aquatic plant improvement. A summary of thirteen (13) suggested methods of restoration are reviewed.

Review of lake restoration procedures

and biological treatments are techno logical alternatives, the choice of process being made mainly on economic grounds. In recent years, combinations of the pro cesses have been successfully used in which the two are usually separate steps in the purification sequence, each making its own contribution to the reduction in the pollu tion load.1-6 In the authors' investigations into the treatment of wool scouring waste liquors, considerable advantage has been found in a combined treatment in which a very rapid biological treatment is followed by a chemical flocculation. This paper shows that the biological step reduces the pollu tion load only slightly, but substantially increases the efficiency of the flocculation. The effects of varying conditions on the process are described, and a mechanism for the improvement in flocculation ef ficiency is proposed. Experimental Three different aerobic biological pro cesses were used to treat wool scouring effluents: plastic medium trickling filter,* a rotating disk apparatus, and a rotating tube reactor similar to that described by Reynolds.7 Their specifications are listed in Table I. The first two were located at local wool scouring mills and the last in the laboratory. All of the units were fed with liquors obtained from the first or sec ond bowls of commercial wool scouring trains. These liquors are equal in strength to the strongest wastes normally discharged from wool scouring mills. The character istics of these liquors are shown in Table II.

McLellon Wm

Papers

Coagulation of colloidal- and solution-phase impurities in trickling filter effluents.