Drip irrigation with waste stabilisation pond effluents: solving the problem of emitter fouling

Abstract

A pilot-scale irrigation scheme was set up in South-West Portugal to investigate the causes of emitter clogging which has been observed when waste stabilisation pond effluents are used for drip irrigation of crops. During field trials over a period of two growing seasons, the operating characteristics of five emitter designs were investigated. Susceptibility of the designs to clogging was compared and the nature of clogging particles was analysed. Those emitters that operated most successfully utilised a long water-path labyrinth to reduce flow to the required level. The operating characteristics of the most effective emitter design are presented in detail. Clogging was shown to result from the deposition and entrapment of sand particles within the emitter labyrinth. Organic material, including pond algae, played a secondary role in the clogging process. Emitter design, rather than water quality, was shown to be the most important factor determining the degree of clogging. It was concluded that pond microalgae alone do not constitute a major hazard to the operation of drip irrigation equipment and that waste stabilisation pond effluents may be safely used for drip irrigation if safeguards are adopted to prevent the contamination of laterals by sand and soil particles. A number of recommendations are made to prevent emitter clogging in future reuse schemes.

Biofilm Accumulation and Structure in the Flow Path of Drip Emitters Using Reclaimed Wastewater

“…The highest PLFA concentrations (emitter A: 201.46 × 10 -3 nmol mm -1 ; emitter B: 141.25 × 10 -3 nmol mm -1 ) in the flow paths occurred after approximately 96 to 144 h of operation, after which the PLFAs dropped rapidly during the next 48 h and then recovered to a certain extent through the end of dosing. This fluctuation of biomass accumulation supports the hypothesis for biofilm formation in the emitter flow path described by Taylor et al (1995): as the biofilm thickness increases, the biofilm organisms become less able to obtain nutrients. Cell death weakens the attachment of the biofilm.…”

“…In addition, there are common microbial sources of emitter clogging, including protozoa and fungi, that form mucous membranes, filamentous slimes, and various adhesive excretions. These biofilms can agglomerate fine mineral and organic particles, producing large flocs that clog the emitters (Adin and Sacks, 1991;Taylor et al, 1995). The growth and development of the aerobic slime-forming bacteria may also cause emitter clogging problems (McElhoe and Hilton, 1974;Ford, 1979).…”

Performance of drippers in two filtering systems using sewage treatment effluent

“…Tajrishy et al (1994) observed the formation of biofilm resulting from the bacterial mucilage and suspended solids in drippers supplied with secondary domestic sewage effluent. On the other hand, Taylor et al (1995) observed that 90% of the drippers showed clogging due to TSE application. Silva et al (2012), studying the use of wastewater generated in cashew nut processing as irrigation water on the clogging of three models of drippers, claimed that the dripper with greatest labyrinth length was more susceptible to clogging.…”

Influência da aplicação de esgoto doméstico tratado no desempenho de um sistema de irrigação

“…Por exemplo, a formação de depósitos gelatinosos, resultantes da interação entre mucilagens bacterianas, algas e zooplâncton, tem sido o fator biológi-co central no processo de entupimento de gotejadores quando se aplicam esgotos sanitários tratados (Ravina et al, 1992(Ravina et al, , 1997. Estudos realizados por Taylor et al (1995) evidenciaram que as interações entre fatores físicos, quí-micos e biológicos foram responsáveis por 90% dos entupimentos de gotejadores. Colônias de protozoários do gênero Ciliatea e de Bryozoa plumatella foram identificadas nos gotejadores entupidos e ao longo das linhas laterais de sistemas de irrigação por gotejamento abastecidos com esgoto doméstico tratado (Ravina et al, 1992).…”