Natural Treatment Systems And Solutions For Wastewater

This research paper will show several types of natural solutions for filtering human wastewater. The solutions will consist of slow-rate systems, rapid infiltration systems, and overland-flow systems. The three solutions will be compared and contrasted in the following fields: distribution methods, land and storage requirements, and collection of treated water. Based upon the research evidence, this paper will show that rapid infiltration systems are the preferred method due to the simplicity of distribution of wastewater, collection of treated water, and the small amount of space it needs for storage.

Natural water treatment has been used for a very long time. Before industrialization and the use of sewage pipes and sewage collection, it was the only method used for filtering human wastewater. Farmers’ used their feces for fertilization, and many people collected their excrements and disposed of them in creeks and rivers (Sheaffer 120). As the waste broke down; the soil, plants, and animals in the habitat consumed and reused the essential ingredients leaving the water supply clean and pure. The same methods are used today; they have been nearly perfected and are used on a much larger scale. Human waste recycling has become a very necessary step toward conserving earth’s water supply (Powledge 9).

When designing a natural wastewater treatment system, there are three major objectives that will help determine which method of treatment is best. Firstly, the waste must be distributed to the land where it is going to saturate into the soil and crops that work as a natural filter. Secondly, the land or area where the waste is going to be distributed must be cultivated to certain needs of each different solution. This will involve construction of the terrain to help filter the water into a collection point. Finally, the naturally filtered water must be collected and transported out of the filtering system (Russell 41).

Rapid infiltration systems distributing process is simpler than the other two systems due to dependability and ease of operation. Slow-rate systems normally use sprinkler systems as the main source of distribution. They can use above ground sprinklers, buried sprinklers, or moving sprinklers. Above ground sprinklers are not favored, because they must be moved during harvest and corrode easily. Moving sprinklers have a pivot point at the center of the field and are rotated around to spread the wastewater evenly. Moving sprinklers tend to corrode, and they also need frequent cleaning. Buried sprinklers work the best, but they are the most expensive sprinkler setup. Buried sprinklers can remain in the crop area during harvest, and if they are maintained properly, they can last for a very long time (Tchobanoglous 953).

Unlike slow-rate systems, rapid infiltration systems use spreading methods instead of sprinkler systems. Spreading in a rapid infiltration system is done with low pressure tubes that flood a filtering basin. The basin is normally one to two feet deep and all surrounding basins should be at the same level for the waste to be spread evenly. Most basins do not have crops inside of them, but some basins have had success using a few types of short, thick grasses (Jensen 6). When solid waste begins to collect on the surface of the basin, the basin must be racked in order to filter better (www.epa.gov).

The overland-flow system uses the spreading method, sprinkler method, and fan spray method. Fan spray and sprinkler methods are used less often due to the fact that they need a buffer zone for over spray caused by wind drifts. Fan Spray and sprinklers clog easily and often times corrode (Tchobanoglous 984-85). The spreading method used in overland-flow systems are spread with gated pipes. The pipes have openings every two feet, and they have plastic doors that are opened to release the wastewater into the fields. The gated pipes are less expensive than fan spray and sprinklers, but they do not spread the waste as evenly (www.epa.gov).

Rapid infiltration systems produce more treated water, take up less space, and require less storage than slow-rate and overland-flow systems. Slow-rate systems cover the largest space of the three systems. Depending on how much output is needed the slow-rate systems size ranges from sixty to five-hundred and fifty acres. A slow-rate system that covers five-hundred and fifty acres can export nearly one million gallons of treated water a day. The land includes service roads, cropped area, buffer zone, and area for storage (Tchobanoglous 963-64). Slow-rate systems also need the largest area for storage of the three systems. During the summer months it must be capable of containing one to three months worth of waste, and in cold regions it must be able to contain four to seven months of waste (965).

Rapid infiltration systems are the second smallest of the three systems with average sizes ranging from two and a half acres to fifty-five acres. Its land consists of access roads, storage area, and basin area. Although the rapid infiltration systems are smaller than slow-rate systems, it can produce one million gallons of treated wastewater a day as well (981-82). Rapid infiltration systems need very little storage space, because it can treat wastewater in any condition hot or cold (Jensen 3).

Overland-flow systems take up only six acres to forty-five acres, and they can produce one million gallons a day during the warm seasons. The sloped cropping area covers the majority of the space needed for the system, but the storage area can be quite large when the overland-flow systems are in an area that has long winters. The systems rely on saturation in the soil, and when the ground freezes the waste must be stored until the ground thaws (Tchobanoglous 990). Even in warmer climates, overland-flow systems must be able to contain two to five days worth of wastewater (Jensen 4).

Rapid infiltration systems can use two different types of recovery; whereas, the other two systems can only use one collection method. Slow-rate systems use underdrainage to collect treated wastewater. Underdrainage is when drain pipes are buried beneath the ground from four feet to ten feet below the surface. The drain pipes create a network beneath the ground, and then moves all of the water to a reservoir or ditch (Tchobanoglous 967-68). The pipe can be from four to eight inches in diameter, and it can be separated from as close as fifty feet apart, and as far apart as three hundred feet (www.epa.gov). The other collection