Using organic fertilizer to mitigate organic-inorganic fouling in agricultural saline wastewater irrigation systems

Recycling saline wastewater for agricultural irrigation offer a promising solution to address both water scarcity and anthropogenic pollution. However, organic-inorganic fouling in saline wastewater irrigation systems (SWIS) poses significant technical and economic challenges. Traditional chemical biocides are currently insufficient for controlling composite organic-inorganic fouling and may pose environmental hazards. This study proposed a greener approach using organic acid (OA) fertilizers to alleviate organic-inorganic fouling in agricultural SWIS. The treatment performances were assessed employing four types of OA fertilizers (i.e., humic acid, alginic acid, nucleotide, and ammonia acid) and a negative control. Results showed that three types of OA, i.e., alginic acid, nucleotide, and ammonia acid, effectively reduced the total SWIS fouling content by 11.2%-57.4%, whereas humic acid exacerbated fouling by 11.2%-57.4%. Specifically, all types of OA significantly mitigated the content of inorganic fouling (precipitates and silicates) by 10.7%-42.3% by forming loosed and sparser structures. However, OA exhibited minimum effects on controlling silica fouling. Meanwhile, except the humic acid, other types of OA decreased the total content of organic fouling by 17.2%-39.5% by reducing the content of humic substances and building block fractions. In addition, the significant binary interactions of organic-inorganic fouling indicated the active role of calcium silica and biomineralization fouling. These findings provide insight into the development of appropriate and eco-friendly antifouling strategies for SWIS, with implications for recycling and reusing saline wastewater.

From farm-scale to lab-scale: The characterization of engineered irrigation water distribution system biofilm models using an artificial freshwater source

Contaminants in freshwater environments, as well as the associated negative impacts on agricultural produce, have emerged as a critical theme of the water-energy-food nexus affecting food safety and irrigation management. Agricultural produce exposed to irrigation with questionable freshwater can internalize and concentrate pollutants. However, the potential risks posed by the ubiquitous presence of biofilms within irrigation water distribution systems (IWDS) remains overlooked, even though such biofilms may harbor and spread pathogenic, chemical, and other environmental pollutants. Our limited knowledge about the role and functional attributes of IWDS biofilms can be blamed mostly to experimental challenges encountered during attempted studies of these biofilms in their natural environments. Hence, a laboratory-based experimental system designed to simulate a freshwater environment was combined with a biofilm reactor capable of recreating the piping environments in water distribution systems. This experimental system was then tested to assess the robustness and repeatability of experimental early-stage biofilms with respect to physical structure and microbial community, using state-of-the-art confocal microscopy and next-generation sequencing, respectively. The results demonstrated the suitability of this laboratory-based experimental system for studying the impacts of selected pollutants on irrigation water distribution systems.

Biofilm research within irrigation water distribution systems: Trends, knowledge gaps, and future perspectives

Biofilms in irrigation water distribution systems (IWDSs) play an essential role in spreading pathogens, chemical pollutants, and environmental pollutants into downstream irrigated crops and thus should be considered a potential threat to food safety. Although the role of biofilms in drinking water distribution systems has been extensively studied in the last decade, the research on IWDS biofilms in this period has been limited. This review identifies research gaps in the field of IWDS biofilms, provides perspectives on experimental designs for investigating IWDS biofilms, and suggests potential strategies worth pursuing in IWDS management. The current state of the art of IWDS biofilms is discussed, and an analysis of the challenges in IWDS biofilm research is presented. Furthermore, this review proposes useful advanced technologies that allow a practical, in-depth fundamental understanding of IWDS biofilms. In a nutshell, this article provides future directions and insights into detailed experimental designs on a relatively under-reported research topic: "IWDS biofilms."