Impact of hydrodynamics on clay particle deposition and biofilm development in a labyrinth-channel dripper

Abstract

In order to better understand physical and biological clogging in drip-irrigation, a study was conducted on the impacts of hydrodynamic conditions on clay particle deposition and biofilm development in drippers using an optical method. A transparent milli-fluidic system composed of labyrinth channels was used to identify areas most susceptible to particle clogging using two different types of clay suspensions: sodium bentonite and kaolin. The impact of salt addition ([NaCl] =200 mg.L-1) on the clay deposition was also analyzed. Biofilm development was studied using the same methodology using a nutritive solution (chemical oxygen demand, COD = 200 mg.L-1). In addition, fluid dynamics simulations were performed along the labyrinth channel to understand the effect of flow behaviour on the fouling. Computational Fluid Dynamics results show two types of flow topology: high velocity in the main flow (around 1m.s-1) and low velocity in the vortex zones (less than 0.2 m.s-1) found in the channel corners. Using an optical method, kaolin deposition and biofilm growth in the dripper were observed to occur mainly in the inlet channel and initial vortex zones, which are characterized by lower mean velocity and turbulent kinetic energy values. This part of the dripper can be considered as a bottleneck that amplifies the fouling phenomena and which should be optimized. With the addition of NaCl, kaolin particles tend to form bigger flocs. Therefore, more significant particle deposition is observed, but this is not the case of bentonite for which no fouling is observed along the dripper.

Background Concentrations of Chemical Elements in Sepetiba Bay (Se Brazil)

“…The lithology of the sediments source area to the studied site is complex (Valeriano et al, 2012), but the analyzed layers have poor mineralogical diversity, which indicates the presence of sediments that were submitted to several reworking and transport cycles and underwent significant mechanical and chemical weathering. deposition of these muddy layers (Ait-Mouheb et al, 2019). Favorable rainy tropical climatic conditions, with dry winters and hot and rainy summers (SEMADS, 2001;Roncarati and Carelli, 2012), promote rich vegetation which is source of organic matter in the study area.…”

Experimental and numerical characterization of the vortex zones along a labyrinth milli-channel used in drip irrigation

“…In this technique, drippers are the most important and critical components (Karmeli, 1977 [20]). Drippers generate low flow rates between 0.5 and 8 [l.h 1 ] for pressure between 50 and 400 kPa (Goldberg et al, 1976 [15]). Dripper flow rate increases with static pressure in a lateral pipe according to a power-law (Karmeli, 1977 [20]): q = k d P x , where q is the dripper flow rate [l.h 1 ], k d the proportionality coefficient that characterizes each dripper, P the working pressure head at the dripper [Pa] and x the dripper discharge exponent.…”

Relações entre características geométricas de gotejadores e dinâmica de obstrução

“…As imagens mostram que no fim do ensaio os canais permaneceram praticamente limpos, não havendo presença de partículas sedimentadas ou desenvolvimento de biofilme. A mesma tendência foi observada para os emissores com largura de canal de 1,0 mm e por isso não foram apresentadas aqui as imagens referentes a esses emissores Mouheb et al (2019)…”

“…Para este emissor observarmos que houve um pequeno aumento na quantidade de partículas acumuladas até 120 h de funcionamento, estabilizando-se após este tempo. Imagens do primeiro defletor dos labirintos com largura de canal de 1,3 mm e relação H/W 1,6 a cada 40 horas de funcionamento A mesma tendência para o desenvolvimento do biofilme no labirinto dos emissores foi identificada porAit-Mouheb et al (2019). Os autores observaram que no início do canal houve desenvolvimento significativo de biofilme, com área de superfície do biofilme cobrindo 67% da largura do canal após 72 h de funcionamento.…”

“…Niu, Liu e Chen (2013) observaram sedimentação de partículas de argila no interior do canal e variações de vazão apenas para concentrações de argila superiores a 1250 mg L -1 enquanto observaram variações de vazão em níveis significativos para concentrações de argila superior a 1000 mg L -1 . A sedimentação de partículas no interior dos labirintos também é influenciada pela natureza das argilas presente na água(AIT-MOUHEB et al, 2019;BOUNOUA et al, 2016;. Desta forma, a pequena concentração de partículas de argila associada às características hidrodinâmicas e natureza da argila, pode ter contribuído com a não formação de agregados, o que impossibilita a sedimentação do material.Os labirintos estudados neste grupo foram desenvolvidos com características construtivas que permitem a formação de vórtices.…”