Agriculture Reference
In-Depth Information
6.1 INTRODUCTION
Increased water demand in domestic, industrial and other sectors causes reduction in
water availability water for agricultural sector. Micro-irrigation system with wastewa-
ter is a viable alternative to overcome the problem of water shortage for agricultural
sector without sacrificing the productivity. However, poor quality of wastewater can
restrict the use of micro irrigation systems due to emitters, which are highly suscep-
tible to clogging by water impurities [8, 16, 24]. The obstruction of emitters affects
the hydraulic performance of the irrigation system, reducing the uniformity of water
distribution, increasing the operating costs and the investment risks, and discouraging
farmers from employing micro irrigation technology. To minimize the limitations of
this system, it is recommended to provide suitable water filtration systems to remove
the impurities (e.g., physical, chemical, or both simultaneously).
In drip irrigation system, quality of irrigation water, fi ltration system and emitter
play a vital role. Wastewater treatment through fi ltration is a key to reduce emitter
clogging. Although an adequate fi ltration system can control emitter clogging with
wastewater [20, 23], yet clogging cannot be avoided completely [29]. The type of
particles in wastewater depends on the source and pretreatment process [2, 3, 31]. The
factors, that infl uence whether a particle is retained by a fi lter, include size, shape,
surface load, settling velocity. Since these factors vary from one type of particle to an-
other, the particle size distribution, the variety of shapes and the density intervals must
also be considered [18]. Extent of dripper clogging was studied by many researchers
in details [10, 25, 30].
The emitter clogging can be classifi ed into three types: physical clogging, chemi-
cal clogging and biological clogging [7]. Physical clogging is caused by suspended
inorganic particles (such as sand, silt and clay), organic materials (animal residues,
snails, etc.), and microbiological debris (algae, protozoa, etc.); physical materials are
often combined with bacterial slimes. Chemical clogging problems are due to dis-
solved solids interacting with each other to form precipitates, such as the precipitation
of calcium carbonate in waters having calcium and bicarbonates [32]. Biological clog-
ging is due to algae, iron and sulfur slimes. De Kreij et al. [11] found that drip-line
with laminar fl ow suffers more severe clogging than the labyrinth type emitter having
turbulent fl ow, because laminar fl ow is predisposed to clogging. Capra and Scicolone
[9] found that vortex emitters are more sensitive to clogging than labyrinth emitters.
Filtering can prevent inorganic particles and organic materials from entering the
drip irrigation system. In India, mostly gravel media fi lter, screen and disk fi lters are
used in drip irrigation system. Gravel media fi lter prevents passage of solid particles,
only if these particles are smaller than the fi lter pores as the capture of particles is con-
trolled by both physical and chemical mechanism [1]. Disk fi lter is simple, economi-
cal, and easy to manage and fi ltration is done at two stages. The larger outer surface
operates as a screen fi lter and collects the larger particles. The grooves inside the disk
allow the adhesion of fi ne particles, mainly organic matter. It retains the particles in
the grooves of the disks. Capra and Scicolone [9] observed that screen fi lters, either
locally or internationally available, were not suitable for use with wastewater, with the
exception of diluted and settled wastewater. They also observed almost similar perfor-
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