Effect of Chlorination and Acidification on Clogging and Biofilm Formation in Drip Emitters Applying Secondary Sewage Effluent

Abstract

Abstract. The risk and inducing mechanism of emitter clogging vary with the types of ions in the irrigation water. The effectiveness of chlorination and acidification treatments in reducing emitter clogging has seldom been comparatively studied. The objective of this study was to quantify the influence of chlorination and acidification in reducing clogging in emitters applying secondary sewage effluent with different types of ions. Two types of emitters with plain channels and one type of emitter with a labyrinth structure were selected to investigate the clogging control strategy by measuring the dry weight of biofilm substance (DW) and the organic matter fraction in the biofilm and analyzing the mineral constituents of the clogging solids and the extracellular polymeric substance (EPS) of the attached biofilm. In general, chemical injection decreased the DW and EPS, resulting in less clogging than in emitters without chlorine and acid injection. For the emitter structures tested, chemical injection was more effective in controlling clogging in plain channel emitters than in labyrinth emitters. Different chemical injections produced similar mineral constituents of the clogging solids: quartz, calcium + magnesium carbonate, silicate, and iron oxide. Chlorine injection interval and targeted acidification pH are both important parameters in determining chemical injection schemes. Under the experimental conditions, weekly chlorination of sewage effluent acidified to pH 6.5 was more effective in reducing the growth and reproduction of microorganisms and the precipitation of solid particles in the drip emitters when applying sewage effluent containing high iron + calcium. However, when sewage effluent containing high calcium was used, acidification was more effective in removing the chemical precipitates. We conclude that the selection of chemical treatment strategies should consider the constituent ions in the sewage effluent. Keywords: Acid injection, Chlorine injection, Extracellular polymeric substance (EPS), Mineral constituents, Microirrigation.

Determining injection strategies of phosphorus‐coupled nitrogen fertigation based on clogging control of drip emitters with saline water application*

“…The results were also consistent with the relatively lower Dra values at the end of the experiments for the E 2 ‐G‐U/(MAP 1 ), E 2 ‐G‐MAP»U, and E 2 ‐G‐U»MAP treatments. For both types of emitters, the DW was negatively correlated with Dra (Table 5), agreeing well with previous studies which demonstrated a greater DW represents more severe clogging in emitters (Zhou et al ., 2013; Hao et al ., 2018). The DW results indicate that a weak acidic fertilizer would be effective in prevention of clogging substances for the plain emitters under G application.…”

“…For each treatment, two emitters were cut at the head, middle, and end segments of a 10 m dripline. These six emitters were used for the DW determination according to the method described in a previous study (Hao et al ., 2018). Assuming the emitter type imposed no effect on the chemical constituent of clogging substances, about 1 g of clogging substances inside the emitters was collected and mixed from the two selected driplines with the same fertigation practice and water quality but different emitter types.…”

“…Under fertigation with alkaline fertilizers, the massive HCO 3 À in the irrigation water might generally react with OH À forming a large amount of CO 3 2À , and then the CO 3 2À and Ca 2+ /Mg 2+ react forming carbonate precipitation (Nakayama & Bucks, 1991;Liu et al, 2019). For the application of acidic fertilizers, however, the H + probably inhibits the carbonate precipitation and even phosphate precipitation while strong acidic P fertilizers are applied (Hills, Nawar, & Waller, 1989;Hao et al, 2018;Ma et al, 2020). Using acidic P fertilizers has been recognized as a method to alleviate emitter clogging, even for the systems with application of saline water that contains large amounts of Ca 2+ , Mg 2+ , HCO 3 À , etc.…”

A Review of the Category, Mechanism, and Controlling Methods of Chemical Clogging in Drip Irrigation System

“…Actually, the active microbial species, water quality, and system operation methods can also directly affect the growth of biofilms [46]. Microorganisms play an important role in emitter clogging by secreting viscous substances to form biofilms [47]. The strong oxidation of chlorine can kill or inhibit microorganisms (bacteria) and prevent the formation of slime and clumps, so as to effectively reduce biological clogging [48].…”

Agricultura irrigada no Brasil: ciência e tecnologia

“…O melhor e mais econômico é prevenir a obstrução (HUANG et al, 2022), mediante projeto de sistema de filtragem compatível com a qualidade da água (DURAN-ROS et al, 2022), além de outras práticas, como a aeração e sedimentação (ZHANG et al, 2021), tratamento químico preventivo (HAO et al, 2018) e até mesmo a abertura do final das linhas laterais para remoção de sólidos depositados no interior das tubulações (LI et al, 2019).…”