Wastewater Fundamentals: Aerobic/Anaerobic Comparison Wastewater treatment has three levels of purification. Primary removes grit and sludge. Secondary removes substances that deplete the naturally occurring dissolved oxygen in the water. Tertiary removes the chemical nutrients, or incorporates them into the microbes. In an aerobic treatment system, biological oxidation converts ammonia and organic matter (mostly manure) to carbon dioxide, water, and microbe cells. Oxygen must be supplied either naturally or artificially to maintain an aerobic system. About half of the organic matter becomes cells, and half becomes carbon dioxide and water. Cellulose, lignin, and inorganic solids are very slowly degraded in aerobic processes. Aerobic organisms grow quite rapidly, permitting a treatment system to adjust to shock or sudden increases in loading. The organic sludge accumulates for eventual disposal. The thick slime characteristic of raw manure is depleted. The high viscosity of manure is reduced to water-like consistency. The cellulose, lignin, and inorganic solids blend with the microbe cells. The sludge settles and flows easily.

The major advantages of aerobic treatment systems are: Relatively odor-free operation Fast rate of biological growth Rapid adjustment to changes in loading and temperature. Elevated temperature is not required. The major disadvantages of conventional aerobic treatment systems are: Oxygen is required Microporous filament, and pure oxygen systems are expensive High production of biological sludge Natural oxidation ponds require large surface area Artificial oxidation ponds have high space, maintenance, and energy requirements Costs for both types of conventional methods has made aerobic systems unsuitable for most livestock operations