Biofouling in milli-labyrinth channels of drip irrigation systems using reclaimed wastewater: A review of optical...

Drip irrigation systems are known for their high water-use efficiency due to the combination of using milli-labyrinth channels to optimise flow distribution and reusing reclaimed wastewater. However, clogging and biofouling remain significant challenges that affect system performance and lifespan. This review provides a comprehensive overview of biofouling in drip irrigation systems, with a focus on how hydrodynamic conditions and nutrient availability in reclaimed wastewater influence the attachment, growth, detachment, and decay of biofilm. The ability of advanced optical techniques, including particle tracking velocimetry, industrial computed tomography, and optical coherence tomography to visualise, measure, and analyse biofouling processes in drip irrigation systems is discussed, along with their strengths and limitations. Additionally, the ability of current biofilm modelling approaches, including both continuum and discrete methods, to simulate nutrient transport, microbial activity, and biofilm-fluid interactions are discussed. By combining insights from experimental data and computational models, this review also identifies key research gaps and presents a new framework for applying biofilm modelling to drip irrigation systems. Future research directions are suggested to improve our understanding of drip irrigation biofouling and to predict it, to optimise emitter design, and increase the overall reliability and sustainability of drip irrigation systems.