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Abstract
The movement to drip irrigation designs that rely on disc filtration over sand filtration means that more colloidal clay ends up in the irrigation system. This colloidal clay then ends up as deposits in the irrigation system, mainly at the end of the property where friction losses and pressure variances are greatest. This deposit of colloidal material then results in uneven water distribution and in the case of fertigation nutrient variances within the property at point source applications. Traditionally growers have been using chlorine and or hydrogen peroxide for drip line maintenance, and some irrigators using surfactants to move clay where flush velocities are insufficient to create sufficient friction for colloidal movement. The aim of this study was to use high molecular weight polymers with flocculating potential to remove colloidal material from drip systems. Preliminary studies showed where flush velocities were greater than>1.5m/sec and delivery capabilities >15mm/ha/day the use of these polymers did not alter flow rates or energy pump efficiency. However, in studies on the Darling and Murray River locations, significant increases in flow rates were achieved through the addition of these polymers (Laminar Flow BioCentral Laboratories), and significant increases in the removal of colloidal material was observed when the polymer was added at 2L/ha at the start of the irrigation shift and coincided with a flushing and cleaning program in comparison to alternative cleaning practices.
Introduction
The Murray Darling Basin is Australia’s largest irrigation region. It produces a range of crops for both export and domestic markets. The water source is largely surface waters sourced from the Murray, Murrumbidgee and Darling River systems. These are all highly turbid waters resulting in growers dealing with colloidal build up in irrigation systems that requires regular cleaning to ensure. Disc filtration has become more popular in Australia in comparison to media filters as they use smaller backflushing water volumes. They also require smaller areas than media filter banks. The downside is that finer colloidal material ends up in the irrigation system that can settle out within lines causing flow reductions, especially in larger systems where flush velocities for cleaning may be reduced at the end of the irrigation design. The industry recommended standard for flushing lateral lines is 0.5m/s.it is interesting to note here that while 0.5m/s is regarded as the industry requirement from personal experience we saw that the higher flush velocity within the shift was preferable and with 1.5m/s flush velocity maintaining system flow rates was possible, whereas with 0.5m/s flow rates in highly colloidal waters was inadequate for maintaining flows within the irrigation design. There are numerous guidelines for irrigators to follow to ensure adequate cleaning of irrigation systems available in Australia and these are readily available both online and within the irrigation industry.
The delivery of irrigation water via pressurised systems through a series of pipes that decrease in size across the length of the design process. In each step there are friction losses in the delivery system(enhanced by sediment loads with the pipe) that can compromise flow rates and pump energy efficiency. There are many research publications on laminar and turbulent flow in terms of energy and water flow, but these are an example of the issues facing primary producers when turbulent flow conditions dominate flow patterns in an irrigation system.
More recently, Garjev et al (2022)documented the potential of laminar flow regimes forming in drip irrigation pipelines. In order to clarify the problem of sustainable use of water for irrigation, it is necessary to analyse the hydraulic and energy-efficient characteristics of water movement in irrigation systems and the conditions under which its transport and distribution to agricultural crops takes place. In the case of polyethylene -PE irrigation laterals for drip irrigation, a water quantity is consumed along their length. Under this condition, the flowrate gradually decreases, and this leads to the formation of different flow regimes along the pipeline. In their study, the question of the length of the part of the PE pipeline with laminar regime is considered, as well as the conditions predetermining the onset of this regime in PE pipelines ф 16/2 and ф20/2. The conditions depend on the number of waters localized outfalls, i.e. drippers, the magnitude of their flowrate, and the distance between them for a given assumed inner diameter and water temperature. The impact of colloidal material and then enhanced flow rate constrictions is something that there is not a lot of research data currently available.
Gry and Bewersdorf (1995) in their publication on drag reduction of turbulent flows by additives noted that as early as 1949 the researcher Thoms observed that minute amounts of long chain polymer molecules could reduce pressure losses in turbulent flow pipes. The resultant drag reduction resulting in significant energy savings on pumped water.
Asidin et al (2019) investigated the drag reduction phenomenon in pipelines which has significant applications in understanding flow rate constrictions in agricultural irrigation systems. They noted that various methods to enhance drag reduction had been developed throughout the years and divided into two categories: non-additives method and additives method. In this work the drag reduction using polymer additives was regarded as one of the more enticing and desirable methods. The potential of polymer additives to reduce drag up to 80% when added in minute concentrations. Reducing drag in the pipe will require less pumping power thus offering economic relieves to the industries. The significance of this work for BioCentral Laboratories led to the development of polymer solutions that would be added in small volumes to the agricultural water stream to reduce drag reduction and increase energy efficient water applications for Australian irrigators.
Abubakar et al (2014) noted that it is a well-known fact that finding sustainable solutions to the unavoidable high pressure losses accompanying pipeline flows to increase the pumping capacity without necessarily adding more pump stations is inevitable. Polymers, as one of the drag-reducing agents which have been found to offer such an economic relieve, is the most widely investigated and most often employed in industries because they can produce drag reduction up to 80% when they are added in minute concentrations. In addition, polymer additives modify the flow configurations of multiphase flows to such an extent that stratification of individual phases is enhanced thereby making the separation of the phases at the fluid destination much easier. The achievements so far made and the challenges facing the use of polymers as drag reducers in turbulent single and multiphase flows are comprehensively reviewed. In their work they note specific areas of interest in the review include phenomena of drag reduction by polymers, factors influencing the effectiveness of the drag reducing polymers, methods of injecting the polymers into the base fluids, degradation of the polymers and industrial applications of polymers as drag reducing agents.
Han and Choi (2017) documented the remarkable ability of polymeric additives to reduce the level of frictional drag significantly in turbulent flow, even under extremely low dilutions, is known as turbulent drag-reduction behaviour. They assessed several biopolymers as promising drag-reducing agents for the potential replacement of high molecular weight synthetic polymers to improve safety and ameliorate environmental concerns.
Hawege and Abushina (2022) also investigated the potential of polymers to reduce drag resistance. They noted that when polymers (DRA) passthrough high shear force areas like pumps and elbows that causes from turbulent flow will lose their drag reduction abilities. In this research, the effect of adding a non-ionic surfactant (tween20) to the cationic polymer in reducing friction in the pipeline has been examined by using rotating disk apparatus to verify its ability in decrease the friction in pipelines. The influence of adding polymer, surfactant and Reynold number in enhancing flow in pipelines were examined. The results appeared that40% drag reduction could be obtained by using this complex.
In Australia with variable water quality and issues surrounding power surges maintaining laminar flow conditions can be a significant but unseen problem with irrigation systems. Turbulent flow results in reduced flow rates in irrigation systems and the potential as noted by Garjev (2022) to significantly impact on flow rate over distance.
BioCentral Laboratories are developing polymer additives to increase laminar flow in irrigation systems to enable primary producers to be more energy efficient in water pumping costs and reduce distribution inefficiencies that occur over distance in water applications.
Australia is faced not only with water that is high in colloidal material but also the high cost of electricity in pumping water that flow rate losses due to friction losses and colloidal build up in irrigation systems is now a considerable cost affecting irrigation efficiency. The aim of this work was to develop a polymer-based product(Laminar Flow) that would address and reduce issues around drag restrictions inflow rate and remove colloidal clays from within the pipe system. The polymers chosen for these studies were in the family of polymers that are used in potable waters so that potential hazards as currently seen with the more commonly used cleaning agents such as chlorine and hydrogen peroxide could be minimised or at least reduced at an operational level.
Materials/Methods
A highly concentrated linear anionic polyacrylamide solution was developed by BioCentral Laboratories to be used as an additive to irrigation systems to assess the impact on flow rates and ability to move colloidal material out of pipeline system.
Product was injected at the start of the irrigation system through the existing fertigation system at 2L/ha. The reason for this approach was to create a laminar flow pathway at the start of the irrigation and from the literature on turbulent and laminar flow suggested that once laminar flow was achieved then the later flow would follow laminar flow patterns within the pipeline system and not revert to a turbulent flow pattern.
Several sites were selected across the Riverland and Sunraysia regions in the Murray Darling Basin to assess flow patterns under a range of irrigation designs and systems operations.
Case Studies
Case Study 1: Palms Vineyards: Mazza Block Merbein
35 acres of table grapes grown from one pump delivery system. The property has both drip and low-level irrigation delivery systems in the property. The aim of this evaluation the 3.5 hectares of Red Globe was assessed in flow rate over a 6-hour irrigation shift. The irrigation system in this instance was low level sprinkler with an output of3mm/ha/hr. 10L of Laminar Flow was injected at the start of the irrigation shift with energy use and flow rate monitored with treated and control irrigation events.
Analysis of the system showed comparable results between the treated shift and the control. This was done twice for comparative purposes and each set of readings were not significantly different. Further analysis of the system revealed that the property had a 15mm/ha daily delivery capability and flush velocities of greater than1.5m/sec. By industry standards this is a system with higher-than-average water delivery capabilities and significantly higher flush velocities than would be normally encountered inmost irrigation designs.
This site was chosen for a study to see if from an assessment of flow pump capacity, a system where normally one would not expect to see flow rate constrictions would a polymer additive like Laminar Flow improve the irrigation system performance. In this instance no significant improvement was made to flow rate. This was an important discovery in that systems could be analysed to determine what are design parameters which could then be extended to growers to determine if polymer additives such as AquaBoostAG Laminar Flow could be expected to result in flow rate benefits.
Case Study 2: Swinstead Melon Farm, Overland Corner, Watermelon, November 2023
Swinstead’s grow watermelons at Overland Corner in the South Australian Riverland. They produce fruit on drip irrigation with 15,100m of tube per hectare with 1L/hr outputs and 20cm spacings. This gives an output in mm/ha/hr of 0.755mm/hr. with low flow drippers friction losses within the system can have a significant influence on the distribution of water and fertiliser within an irrigation shift and maintaining clean driplines is acritical part of on farm maintenance over the growing season. The assessment was the impact that AG Laminar Flow applied at 2L/ha at the start of an irrigation shift would have on flow rates within the irrigation shift.
For physical flushing of sediment, it is recommended that a minimum of 0.5m/s is required to physically remove sediment build up in the dripline. From the observation of the picture, it is noticeable that this flush line does not have 0.5m/sec flush velocity. This was the end of the section where the sediment load was expected to be at its highest. The hand over the water flow is checking for lumps of sediment being flushed through the system.
Table 1: flow rate post treatment over time.
Table 1 shows the flow rate prior and post treatment. Flowrate variations can be expected to occur with higher sediment loads and as such seasonal variations would be anticipated to occur. In this instance prior to the addition of the Laminar Flow product, flow rates of 60m3/h were being recorded. Post the addition of the AquaBoostAG Laminar Flow, Polymer flow rates increased to 67.60m3/h and 68.57m3/h. This represents an increase of 13% in flow rate from the application of AquaBoostAG Laminar Flow.
The increase in flow rate post treatment with AquaBoostAG Laminar Flow indicates friction loss reduction so that higher flowrates are recorded at the lock 1 meter in this instance.
Case Study 3: AVL Vineyard Pomona NSW
AVL operate a large vineyard on the Lower Darling near Wentworth in NSW. Water from the Darling at this location has high turbidity levels that result in continual flushing to clean the irrigation system. The floods of 2022/23 have also contributed to significant sediment loads in the irrigation system and had significantly impacted on irrigation efficiency systems within the property.
AG Laminar Flow was provided to treat an irrigation shift as part of the post-harvest cleaning operations in March 2024.Pictures were taken by AVL staff pre and post the application of AquaBoostAG Laminar Flow
Pictures 3 and 4 (below): Flushing of valves pre and post application of AquaBoostAG Laminar Flow (pictures courtesy of AVL).
What is noticeable in these pictures is the visual impact of turbulent versus laminar flow. The flow prior to treatment with AquaBoostAG Laminar Flow shows the tubular flow patterns as caused by increased friction within the pipe and reduced flush velocity which, while indicating higher colloidal levels by the colour of the flush water, also reduces the ability of the flow to physically move colloidal material out of the pipeline.
Case Study 4: Century Orchards Loxton South Australia
Century Orchards are almond growers located at Loxton in the Riverland of South Australia. They take water from the CIT irrigation system and being based at the end of the pipeline, management and cleaning of colloidal buildup is a constant focus of the irrigation division of the company.
A field evaluation was set up on the14/8/24 to inject AquaBoostAG Laminar Flow at 2L/ha and conduct a cleaning irrigation run in some of the sections at the far end of the property where colloidal buildup has been identified.
The pictures below are part of the case study undertaken at Century Orchards and presented at the ASEAN Irrigation and Drainage Conference, Sydney 2024, on the impact of Laminar Flow in system maintenance. Century Orchards undertake significant monitoring and measuring the irrigation system performance as can be seen by not only high-resolution imagery but also water monitoring.
Conclusion
Irrigation flow characteristics are highly variable and need to be understood on a site-by-site basis to understand system efficiencies and flow characteristics. This can be done through a few mechanisms including soil water monitoring, high- and low-resolution imagery, pump energy and flow rate monitoring to determine where and if laminar and turbulent flow issues are affecting individual properties. In general, higher irrigation delivery systems with high flush velocities are less likely to have flow constraints and sediment buildup in comparison to systems that are larger and operate under lower operating pressures.
The use of AquaBoosAG Laminar Flow in these and other studies can be seen to be very effective in sediment management in drip irrigation systems. Physically, laminar flow patterns could be seen with flush terminals and increased pump flow rates recorded in most sites.
AquaBoostAG Laminar Flow offers the irrigation industry a low-cost safe means of cleaning irrigation systems of colloidal clay and improving flow rate efficiency.
References
Abubakar A., Al-Wahaibi T., Al-Wahaibi Y., Al-Hashmi A.R.,Al-Ajmi A.: Roles of drag reducing polymers in single- and multi-phase flows. Chemical Engineering Research and Design. V.92, I 11, p2153-2181, 2014
Asidin M.A., Suali E., Jusnukin T.,Lahin F.A.: Review on the applications and developments of drag reducing polymer in turbulent pipe flow. Chinese Journal of Chemical Engineering 27 (2019)1921–1932
Gry A., Bewersdorf W.: Drag Reduction of turbulent flows by additives. Springer Science. 1995
Gadjev R. et al: On the Laminar Flow Regime Forming in Pipelines for Drip Irrigation. 8th International Conference Energy Efficient and Agricultural Engineering,
Han W.J., Chio H.J., Role of Bio-Based Polymers on Improving Turbulent Flow Characteristics: Polymers 2017, 9(6), 209;https://doi.org/10.3390/polym9060209
Hawege E., Abushina A.: Study Influence of adding Surfactant to polymers in Reduce Friction in Pipelines. Libyan Journal of Science &Technology 9(2), 2022
