Backwashing performance of self-cleaning screen filters in drip irrigation systems

Abstract

The self-cleaning screen filter is one of the most common types used in drip irrigation systems. Backwashing pressure difference and backwashing time for two screen filters with one geometry and two different screens (178 μm and 124 μm) using two water qualities (tap water and sand–water mixture) were studied in a total of 88 runs (42 runs for tap water, 22 and 24 filtration cycles for sand–water mixture and backwashing, respectively). The backwashing pressure difference and backwashing time were calculated using the experimental data, and the results were largely in the range of measured values. Three constraint conditions (flowrate, sand condition and filtration time) of backwashing pressure difference were analysed, and the optimal values of backwashing pressure difference were given as 60.0 and 70.0 kPa for 178 μm and 124 μm filters, respectively. The backwashing time of the screen filter should be an optimal value that ensures that the pressure difference between the internal and external surfaces of the screen decreased to the initial value, and the sand concentration of the backwashed outlet decreased to a small, stable value. Based on the results of the backwashing experiment and prototype observation, the optimal backwashing time was given as 30 to 45 s for both screen filters.

Sewage Performance of a New Type of Flap Filter

“…Therefore, the influence of the influent flow rate on the discharge process was greater than the influence of the influent sand content. This result was consistent with the research results of the relevant experts in the study of mesh filters (Zong et al 2019； Song, 2017； Li et al 2014. Combining the analysis of the principle of mass conservation and the principle of sediment carrying in water flow, under the same working conditions, the larger the influent flow is, the stronger the sediment carrying capacity, the shorter the sewage discharge time, and the better the filter cleaning effect.…”

A virucidal face mask based on the reverse‐flow reactor concept for thermal inactivation of SARS‐CoV‐2

“…The cyclic nature of breath, too, presents a natural mechanism of filter clearing. Exhalation, when the flow reverses direction within the mask, would backwash the filter medium, potentially releasing and expelling any particle contaminants present 74 . In general, care must be taken to design a system, which is able to retain, inactivate, and then emit that inactivated pathogen of interest without irreversibly capturing other contaminants.…”

“…Exhalation, when the flow reverses direction within the mask, would backwash the filter medium, potentially releasing and expelling any particle contaminants present. 74 In general, care must be taken to design a system, which is able to retain, inactivate, and then emit that inactivated pathogen of interest without irreversibly capturing other contaminants. In the case where periodic replacement of the mesh material within the mask is necessary, a cheaper and less complex mesh material would be favored.…”

Assessment of Different Pressure Drop-Flow Rate Equations in a Pressurized Porous Media Filter for Irrigation Systems

“…Similarly, values of 1/α and C 2 for the Darcy-Forchheimer Equation ( 9) were derived from a parabolic regression fit through the origin. Finally, coefficients C o and C 1 of the power function Equation (11) were obtained after a linear regression fit of log (−S i ) (see Table 2 and Figure 2). Most of the power functions proposed in the literature (see [13,30]) modify the v s exponent of the Darcy-Forchheimer inertial term while maintaining the permeability one linear with v s (i.e., S i = Mv s + Nv λ s with M, N and λ constants).…”

“…In filtration mode, pumping work is needed to achieve a nominal flow rate, being proportional to the pressure drop through the filter [10]. Total filter pressure drop increases as particle retention in the packed bed progresses, eventually reaching a threshold value beyond which the backwashing regime begins [11]. In the latter mode, pumping work more intense than that of filtration is required to develop fluidization of the granular bed assuring particle removal [9].…”