The status of the National Irrigation Return Flow Research and Development Program is presented. Current research projects and future program development are discussed. The report represents the position of the Environmental Protection Agency (EPA) with regard to the development of effective controls on the quality of irrigation return flows. Program goals and milestones are outlined. A number of potential control measures are discussed. Improvements in the water delivery system, on-the-farm water management, and the water removal system are considered with respect to improving the quality of irrigation return flows and decreasing the degradation of receiving waters. Research and investigations are needed to evaluate the effectiveness of potential control measures. Demonstrations and educational activities will be required to overcome institutional, political, and legal constraints to water management reform.

The introduction of sulfite waste liquors into streams often leads to the development of unsightly masses of biological slime dominated by Sphaerotilus. One approach for controlling the development of Sphaerotilus in streams receiving pulp mill wastes has been to employ biological methods for treating wastes before release into a receiving stream. The study evaluates the slime growth potential of pulp mill wastes treated by various methods of biodegradation. Wastes were tested both before and after secondary treatment in order to determine the type of biodegradable material present in the influent, determine the extent of fermentation during treatment, and the amount of biodegraded fermentable compounds discharged in the effluent. These studies were carried out in an effort to define total carbon, readily fermentable carbon, and to design a reasonably accurate and sensitive method for predicting adequate water quality presently measured by BOD.

Experimental studies were undertaken to examine the flow in long vertical conduits with particular reference to the design of storm water drop shafts. A distinguishing characteristic of such flow is the potential cavitation regime. Its existence depends upon the design of the structure. The cavitation regime will develop when the conduit is sufficiently long and the head sufficiently large. It can also be generated at a lower head if a control valve is installed in the supply line so that the net head can be negative. If a small amount of air is introduced into the system, the cavitation region is eliminated, the pressure gradient is more uniform, and the flow consists of a uniform mixture of air and water.

A shipboard sewage treatment system consisting of: Comminution of solids for ease of transport and further treatment; Electro coagulation of sewage for ease of removal of suspended solids; Solids separation; Soluble BOD reduction with carbon adsorption; Coliform bacteria removal; and Solids incineration was designed to process shipboard sanitary, culinary, and laundry wastes during prolonged sea trials. Advantages of the electrochemical system are given. Waste stream characterization showed the BOD and suspended solids levels of shipboard wastes to be 2 to 3 times the concentrations common to municipal wastes. The development program was successful in demonstrating a practical and economically viable electro-chemical treatment system.