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Configuration and Substrate Design Considerations for Constructed Wetlands Wastewater Treatment
Published in Donald A. Hammer, Constructed Wetlands for Wastewater Treatment, 2020
Gerald R. Steiner, Robert J. Freeman
Small communities with wasteflow less than 380 m3/day should have a simple primary treatment system preceding the CW. Septic tanks can serve individual or clusters of homes with an alternative sewer system such as septic tank effluent pumping (STEP). An Imhoff tank or septic tank(s) requires sludge removal and drying beds or disposal to a large system. Larger communities may require a more complicated sedimentation tank system with sludge digestion and sludge-drying beds.
Anaerobic Systems
Published in Subhash Verma, Varinder S. Kanwar, Siby John, Environmental Engineering, 2022
Subhash Verma, Varinder S. Kanwar, Siby John
An Imhoff tank is an improvement over a septic tank in which sludge and incoming wastewater are kept in separate units or chambers. The upper chamber is called the sedimentation chamber and the lower chamber is called the digestion chamber, as shown in Figure 27.5. Imhoff tanks are much deeper than septic tanks.
Wastewater management in small towns – understanding the failure of small treatment plants in Bolivia
Published in Environmental Technology, 2018
Claudia Cossio, Jennifer McConville, Sebastien Rauch, Britt-Marie Wilén, Sahar Dalahmeh, Alvaro Mercado, Ana M. Romero
The types of technologies included in this study are considered representative of treatment systems implemented in Bolivia in the last decades, where stabilization ponds (46%) and Imhoff tanks (16%) are the most common technologies. In the region where this study is implemented, these two technologies represent 39% and 27%, respectively [8]. Table 1 provides the description of the studied treatment plants and the process units implemented. In addition, schematized treatment processes are provided as supplementary information. The Imhoff tank is a primary treatment technology designed to remove TSS. It includes a sedimentation chamber for the wastewater and a sludge digestion chamber in the bottom of the same infrastructure. The Imhoff tank became popular because it occupies little space and is a relatively inexpensive investment.
Design methodology for sewage water treatment system comprised of Imhoff ‘s tank and a subsurface horizontal flow constructed wetland: a case study Dakhla Oasis, Egypt
Published in Journal of Environmental Science and Health, Part A, 2022
The Imhoff tank is divided into two sections: an upper sedimentation zone and a lower accumulation and sludge digestion zone. The same factors that rule all primary sedimentation processes, such as the surface load rate, detention time, and horizontal velocity, influence the design of an Imhoff’s tank to a large extent.[30] To ensure the system's sedimentation and sludge digestion processes run smoothly in the Imhoff Tanks' [30] recommended the following design criteria: (i) surface loading rates vary from 20 to 40 m3 m−2 d−1, (ii) detention time varies from 2 to 4 hours, (iii) length to width ratio vary from 2:1 to 5:1, (iv) slope of settling compartment ratio 1.25:1 to 1.75:1, (v) slot opening in varies from 150 to 300 mm, (iv) scum baffle below surface varies from 250 to 300 mm and above surface is 300 mm, and (iiv) freeboard varies from 450 to 600 mm. Design criteria for gas vent are, area as a percent of the total area varies from 15 to 30% and the width of gas vent opening varies from 450 to 760 mm. In addition, the sludge digestion section, (i) storage capacity ranges from 4 to 8 months, (ii) volume varies from 0.06 to 0.1 m3 capita−1, (iii) sludge withdrawal pipe varies from 200 to 300 mm, (iv) depth below slot to top of sludge varies from 0.3 to 1 m, and (v) total water depth (surface to tank bottom) varies from 7 to 9.5 m. Figure 3 show typical plan views and cross sections of the Imhoff’s tank components. A pretreatment using Imhoff’s tanks with an effective volume of 125 m3 is constructed before the HSFW to lower the amounts of solids in the input and to lessen the danger of clogging of the HSFW (filter bed). The sludge that settles in the digester chamber must be removed on a regular basis (twice per year). It's sent to the Hama drying basins treatment facility. When the sludge volume in the settling chamber exceeds 2/3 of the usable height in the settling chamber, it must be removed. Finally, the sludge treatment system for treating and composting the main sludge accumulated in the Imhoff tank permits nutrients to be reused as high-quality crop fertilizer. Table 2 summarizes the designed Imhoff’s tanks and the influent and the expected effluent pollutants concentrations.