Emitter and filter tests for wastewater reuse by drip irrigation

Agriculture is the main user of water in Italy, as in most regions of the world. Particularly in
Mediterranean regions, where it is more difficult to meet the agricultural water demand with conventional
resources,wastewater reuse represents a viable option. Drip irrigation is particularly suitable for
wastewater reuse because it minimises the health risks to farmers and product consumers due to contact
with thewastewater. The performance of drip irrigation systems usingwastewater is mainly limited by
emitter clogging, and this discourages farmers from introducing it. The paper gives the results of experimental
trials on the behaviour of six kinds of filters (gravel media, disk and screen) and four types of
drip emitters (vortex and labyrinth) using five kinds of municipal wastewater that have not undergone
previous advanced treatment. The performance of the emitters and filters tested depends on the quality
of thewastewater: total suspended solids and organic matter content influence the percentage of totally
clogged emitters, the mean discharge emitted, the emission uniformity coefficient, and the operating
time of the filter between cleaning operations. Vortex emitters were more sensitive to clogging than
labyrinth emitters. The gravel media filter guaranteed the best performance, but the disk filter, which is
cheaper and simpler to manage, assured performance similar to that of the gavel media filter. The test
showed the importance of the technology used in manufacturing disk filters. Screen filters were shown
to be unsuitable for use withwastewater, with the exception of diluted and settledwastewater. The theoretical
discharge of filters, suggested by the manufacturers for clean water, is not adequate for wastewater
of the kind used in the trials (suspended solids greater than 78 mg/l and BOD5 more than 25 mg/l
of O2). The operating times of the filters between cleaning operations, less than 1 h in most trials,
suggest the use of automatic cleaning systems. The existing clogging risk classifications proposed for
clean water can only be considered reliable for wastewater when labyrinth emitters and gravel or good
quality disk filters (such as Arkal) are used; they are not adequate for vortex emitters or screen filters.
© 2004 Elsevier B.V. All rights reserved.