Full-scale tests were conducted on two variable-slope test sewers (12- and 18- inch diameters). During the tests, solids were first allowed to build up in both test sewers by passing domestic sewage through the sewers for durations of 12 to 40 hours and then were removed by hydraulic flushing. Formulas were developed which gave satisfactory predictions of several cleansing efficiencies and wave depths for the flush waves and sewer sizes studied. A prototype flush station developed can be inserted in a manhole to provide the functions necessary to pick up sewage from the sewer, store it in a coated fabric tank, and release the stored sewage as a flush wave upon receipt of an external signal. An estimate of costs of periodically flushing combined sewer laterals are given.

Synthetic acid mine drainage (AMD) water was prepared by draining tap water through waste coal, and the resulting AMD was treated on a laboratory scale by an electrolytic oxidation process. Tests of fluidized bed, packed-bed, and annular flow prototype reactors demonstrated the packed-bed reactor to be most efficient. Oxidation of Fe² to Fe³ takes place on a carbon electrode at a mass transport limited rate, while hydrogen evolution occurs on a polished 316 stainless steel cathode, limited by a slower electrochemical kinetic step. Preliminary economic analyses, using a packed-bed reactor are given. The electrolytic process is free from both the safety hazards associated with radio isotope-induced oxidation and the temperature dependence of biological oxidation methods.

Coal mining produces a variety of environmental problems -- acid drainage, sedimentation, surface subsidence and surface scars. The study reviews the response of legal institutions to those problems in Maryland, Ohio, Pennsylvania and West Virginia. Technological and economic concerns are also taken into account. The study discusses the antecedents of today's Appalachian coal industry and the environmental problems it has created. It examines the way in which the property system allocates rights in coal and coal lands, the efficacy of litigation and present laws and regulations for preventing environmental damage, and constitutional limitations on the ability of states to effectively respond to the problems. A case study of the economics of the Maryland coal industry is also presented. Model legislation giving the states the necessary powers to respond to environmental problems, is proposed.

Operational criteria, design and operations costs for a treatment facility to remove nitrogen from agricultural tile drainage in the San Joaquin Valley were further investigated during 1970 at the Interagency Agricultural Wastewater Treatment Center near Firebaugh, California. The year-long study period is identified as Phase II. Based on projected nitrate-nitrogen concentrations for valley tile drainage water, the research in this phase extended earlier Phase I studies on the feasibility of bacterial denitrification by filters and covered ponds.

To relate basal nutrients in the water and on the bottom of a warm, fresh water stream to their ability to support growth and multiplication of pathogenic and nonpathogenic enteric bacteria, three studies were designed including a river water quality analysis, respiration experiments, and continuous culture experiments. The presence of coliform bacteria primarily not producing intestinal disease, serves as indicators for potentially infectious microorganisms. Any growth by either coliform bacterial group or the disease producing organisms in the natural aquatic environment could significantly alter our present concepts of detection and surveillance of these organisms. Tests in detecting and analyzing polluted waters, and from levels of the self-purification potential, showed that Oconee River, a typically non-polluted stream of the North Georgia piedmont, is capable of supporting bacterial growth including coliforms.

Pilot plant studies were conducted to develop and demonstrate the capabilities of the deep bed, dual media, high rate filtrate treatment process for storm caused combined sewer overflows. The treatment system is comprised of a drum screen with a 40 mesh screening element (420 microns opening) followed by a deep bed, dual media, high rate filter of five feet of No. 3 anthracite (effective size 4 mm) over three feet of No. 612 Sand (effective size 2 mm). The results show suspended solids removals of 93 percent, with polyelectrolyte addition, at a filtration rate of 24 gpm/sq ft at an average influent suspended solids of 411 mg/l. Reductions in biochemical oxygen demand averaged 65 percent. Capital costs and operating costs for a high rate filtration plant are given. Principal advantages of the proposed system are: high treatment efficiencies, automated operation, and limited space requirements as compared with alternate flotation or sedimentation systems.