Herman Bouwer

Land Treatment of Wastewater

Publisher Summary This chapter describes land treatment of wastewater and discusses the selection and design of system for land treatment. Minimum impact on the environment and minimum total cost of operation are the two main design criteria for land treatment of liquid waste. The choice of system is largely controlled by soil and hydrogeologic conditions and by the availability of land. The chapter divides land treatment systems into three types: overland flow systems, low-rate application systems, and high-rate application systems. Overland flow systems are used where the soil is too impermeable or the suspended solids content of the wastewater is too high to allow significant infiltration rates, causing most of the wastewater to run off. With low-rate application systems, all wastewater apply infiltrates into the soil, but the dosages are rather small and of the same order as the water requirements of the crop or vegetation. With high-rate application systems, all wastewater again infiltrates into the soil, but the dosage is much greater than that necessary for crop growth.

Comparison of methods for calculating vertical drainage and infiltration for soils.

Abstract The Youngs, Gardner, Ligon, and numerical analysis techniques for calculating the amounts of one-dimensional, vertical drainage from soil are discussed and compared with each other and with observed data, where possible. The same was done with the Green and Ampt, Philip, and numerical analysis methods for calculating the amounts of infiltration into soil profiles. Numerical analysis gave the best agreement with the observations, but required considerable input data and the calculation procedure was not simple. The Youngs drainage equation and the Green and Ampt infiltration equation were the easiest to use and gave reasonably accurate results, which are probably sufficient for most field problems.

Organic contaminant behavior during rapid infiltration of secondary wastewater at the phoenix 23rd avenue project

Abstract Movement of trace organic pollutants during rapid infiltration of secondary wastewater for groundwater recharge was studied at the 23rd Avenue Rapid Infiltration Project in Phoenix, Arizona. Samples of the wastewater applied to the spreading basins and of renovated water taken from monitoring wells were characterized for priority pollutants and other specific organic compounds using gas chromatography/mass spectrometry. The concentrations of organic constituents were affected by volatilization, biodegradation and sorption processes. Nonhalogenated aliphatics and aromatic hydrocarbons exhibited concentration decreases of 50–99% during soil percolation. Halogenated organic compounds were generally removed to a lesser extent. Concentrations of trichloroethylene, tetrachloroethylene, and pentachloroanisole appeared to be significantly higher in the renovated water than in the basin water, reasons for this behavior remain unclear. Many organic contaminants were detected in the groundwater indicating such systems should be designed to localize contamination of the aquifer. Chlorination of the wastewater had no significant effect on concentrations and types of trace organic compounds.

Irrigation and Global Water Outlook

While the earths renewable water resources are finite, the earths population continues to increase and requires more and more water for municipal, industrial, agricultural, environmental, recreational and other needs. Water resources must be better managed on a local, regional, national, and international scale. This includes providing more storage of water during times of water surplus, minimizing water losses, increasing food production per unit of water, transferring water to uses with higher socio-economic returns, and reusing wastewater. Sewage effluent often already is indirectly used, but water reuse in the future must be better planned as sewage flows increase, the public health and surface water quality need to be protected, and edible crops need to be irrigated. Planned water reuse requires adequate treatment so as to meet the quality requirements of the intended reuse. Agricultural and urban irrigation will play an important role in water reuse, especially in dry climates.

Theoretical effect of unequal water levels on the infiltration rate determined with buffered cylinder infiltrometers

Abstract Differences in water level between cylinder and buffer of a buffered infiltrometer installation cause the infiltration rate as calculated from outflow from the inner cylinder to be in error. The author determines the error in relation to the water level difference between cylinder and buffer, the diameter and depth of installation of the cylinder, and the final hydraulic gradient.

Urban and agricultural competition for water, and water reuse

Abstract Competition for water can be resolved by construction of more facilities for storing water in wet years for use in dry years, by weather modification, watershed management, urban and agricultural water conservation, reuse of sewage effluent and other wastewater, desalination of saline water, water banking and transfer of water rights or other changes in water use. Reuse of wastewater requires treatment so that the water meets the quality requirements for the intended reuse. Groundwater recharge and recovery can play an important role in the treatment and storage of wastewater for reuse—agricultural, urban, and industrial, as well as potable. Often, water shortages are only shortages of cheap and abundant water, and competition problems can be resolved by good planning and management if the public is willing to pay the price and to accept changes in water use.

Future of irrigation in balanced third world development

Abstract Almost 80% of the world population lives in developing countries and 80% of these people live in small settlements or villages and are the ‘rural poor’ whose lives often are plagued by serious health, water and sanitation problems and food shortages. Many countries have changed from self sufficiency and exporters of food to importers of food. Food production often can only be increased by improving or rehabilitating existing irrigation systems and by building new irrigation projects. Yet, the rate of growth in world irrigated area has greatly decreased in the last decade. For North America, the irrigated area has actually decreased. Around cities, sewage effluent will become increasingly important as a water source for irrigation. By the year 2000, there could be 18 megacities with more than 10 million people each in the Third World. Energy sources must be developed to meet the needs for irrigation and fertilizer manufacture. Development of the Third World must simultaneously take place in all key sectors (irrigation, agriculture, water supply, health, energy, education etc.), so that a balance is achieved and progress in one sector is not hampered by stagnation in another. Balanced development must also use both hard technology (roads, canals, structures, machinery, technology etc.) and soft technology (social structure, human interactive processes, motivational techniques, social participation etc.).