Overview and Types of Wastewater Land Treatment System (1)

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1 Overview of wastewater land treatment system

Wastewater land treatment system is the irrigation system of Bunzlau, Germany, which used land to treat wastewater and sludge in the 19th century, and then it was introduced to the United States and developed rapidly
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Research shows that the wastewater land treatment system has the characteristics of low investment, simple operation and management, removal of pollutants such as nitrogen and dephosphorization, wastewater reuse, and alternative to secondary treatment or even tertiary or advanced treatment

The land-based wastewater treatment system in China was developed in the 1980s
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Land Processing System (LandProcessing System) is defined as: sewage undergoes a certain degree of pretreatment, and then is distributed to the land in a controlled manner, using soil filtration and adsorption-microbes-the self-purification function and self-regulation mechanism of the plant ecosystem, through a series of The processes of physics, chemistry and biochemistry make the sewage reach the predetermined treatment effect, and utilize the resources such as nitrogen and phosphorus in the sewage, making it a sewage treatment technology for plants' own nutrients

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2 Types of wastewater land treatment systems

The wastewater land treatment system is divided into five types: rapid infiltration (RI), slow infiltration (SR), surface overflow (OF), underground infiltration (SWIS), and wetland system (WL) according to different treatment targets and objects.
Process type
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1 Overflow (OF system)

Surface flooding is the spraying of wastewater on the sloping land with vegetation, making it a thin layer of runoff along the surface, and the runoff water is collected by the collecting tank, as shown in Figure 8-3
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The surface flooding treatment system mainly deals with wastewater.

Figure 8-3 Surface flooding system

Generally, the surface overflow soil is clay and sub-clay with poor water permeability, and the site should have a slope of 2% to 6%, and the ground should have no obvious unevenness
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When the wastewater flows downhill, part of it infiltrates into the soil, and a small amount of evaporation occurs.
The suspended solids in the water are filtered and intercepted, and the organic matter is oxidized and decomposed by the microorganisms living in the grass roots and topsoil

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2 Rapid percolation (RI system)

Rapid infiltration is named after the sandy loam or sandy soil infiltration with the coarse-grained structure with strong soil permeability of the treatment site
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The wastewater is batched on the ground in an intermittent manner.

Figure 8-4 Rapid infiltration system

It is better to use rapid infiltration effect in the place where the groundwater level is low or the groundwater quality deteriorates due to salt water intrusion.

The reason is that the water level can be raised or the hydraulic gradient can be reversed, so that the groundwater can be protected from the harm of water intrusion

The hydraulic load of rapid infiltration can reach more than 30m/d, and most of the rapid infiltration systems do not recover the treated water, so the floor space and treatment cost are smaller than that of surface flooding and slow infiltration
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Rapid percolation generally requires pre-treatment to reduce the concentration of SS in wastewater to prevent clogging of the filtered soil

Related Links: Analysis of the Effect of Constructed Wetlands on Domestic Sewage Treatment