Impact of recycled water irrigation on soil salinity and its remediation

Continuous use of recycled water (treated wastewater) over a long period of time may lead to the accumulation of salt in the root zone of the soil. This is due to the relatively higher levels of salt contained in the recycled water compared to a town water supply. The increase in salt concentration in the soil can adversely influence the amount of water a plant can uptake from the soil due to the osmotic effect. Despite significant benefits, recycled water may deteriorate soil health in terms of increased salinity and sodicity. Although several studies in the past have highlighted the increase of soil salinity due to recycled water irrigation, the phenomenon depends on the variability of soil characteristics. In this study, the impact of using three different types of irrigation water (with electrical conductivity 0.2, 0.8, and 2.0 dS/m) on the mechanism of salt accumulation in the soil was investigated. To contribute to the addition of the existing knowledge of soil salinisation, soil from two paddocks (i.e., D33 and Yarramundi) in Western Sydney, Australia were analysed, and relationships among parameters associated with salt accumulation were evaluated using the results from continuous column studies. Results show that if the irrigation is conducted with high saline water, there is a possibility for salinisation of soil to occur. To prevent this from occurring, one of the solutions could be to use a normal town water supply for irrigation at some intervals. This will allow for the leaching of excess salt accumulated in the soil to deeper layers

Irrigation in urban landscapes : effectiveness of recycled water for sporting fields

This study aims at evaluating the effect of applying different types of recycled water on Kikuyu grass which is a very popular turf grass used for Australian urban lands as well as sporting fields. Three identical columns were irrigated with tap water (TW) as control water and two types of treated wastewater namely MBR (Membrane Bioreactor) and IDAL (Intermittently Decanted Aerated Lagoon). Salinity level for both treated wastewaters was similar while MBR had a higher level of nutrients compared to IDAL. Grass dry matter yield and nutrient level were monitored and analysed regularly. The highest dry matter yield was achieved from the column irrigated with MBR. The second highest dry matter yield obtained from potable water and amount of dry matter yield from IDAL was far lower than the other two columns. Based on these results, it can be concluded that it is more beneficial to sue secondary treated wastewater for irrigation of urban lands, thus saving in water and chemical fertilisers. Moreover, significant saving in the treatment costs can be achieved by not adopting tertiary of advanced treatment system

The effect of irrigation using secondary and advance treated wastewaters on soil properties under kikuyu grass production

The main objective of this study was to determine the effect of irrigating using three different types of waters, viz. secondary treated wastewater (STW), advance treated wastewater (ATW) and tap water (TW) on some important soil characteristics under kikuyu grass production. Kikuyu grass (Pennisetum clandestinum) is a very common and popular grass for urban areas and sports fields in Australia and was irrigated with above-indicated wastewaters and tap water for a period of 16 months (March 2016 - June 2017). No fertiliser was added during the study. Irrigation waters, soil extracted waters from different depths of the soils and soil samples from different depths were analysed for different parameters. Considerable changes occurred in soil characteristics over the period of study under different treatments. Soil saturated extract pH (pHSE) experienced an increase of more than 1 unit under irrigation with ATW while STW irrigated soil showed no appreciative change and TW irrigated soil evidenced a slight decrease of pH compared to initial soil pH. Also, a remarkable increase recorded for saturated extract electrical conductivity (ECSE) of top soils irrigated with treated wastewaters compared to soil’s initial ECSE. Variation of soil pHSE in conjunction with soil salinity and differences in nutrient levels amongst irrigation waters resulted in various grass yield from each treatment. Annual grass production of 16,241 kg of dry-matter per hectare (kg DM/ha) achieved from soil irrigated with STW where the recorded annual yields from ATW and TW were 7,028 and 14,216 kg DM/ha, respectively. Overall, the results from this study highlighted the benefits of using STW as irrigation water due to its lower cost of treatment compared to ATW, higher grass production and maintaining of soil pH within an ideal range

The effect of irrigation using recycled waters obtained from MBR and IDAL wastewater treatment systems on soil pH and EC under kikuyu grass (Pennisetum clandestinum) production

The main objective of this study was to determine the effect of irrigation using three different types of waters, viz. treated wastewater through membrane bioreactor system (MBR), treated wastewater via intermittently decanted aerated lagoon process (IDAL) and tap water (TW) on soil pH and EC under kikuyu grass production. No fertiliser was added during the study period (one year). Irrigation waters, waters extracted from different soil depths and soil samples from different depths were analysed in laboratory. Considerable changes occurred in soil characteristics over the study period under the various treatments. Soil pH increased more than 1 unit under irrigation with treated wastewater produced by IDAL system while soil irrigated with treated wastewater from MBR treatment system showed little change and TW irrigated soil evidenced a slight decrease when compared to pH at the beginning of the study. Also, a remarkable increase was recorded for EC1-5 of top soils irrigated with treated wastewaters compared to soil's initial EC. The results from this study highlighted the benefits of irrigation with treated wastewater through MBR system due to its lower cost of treatment compared to IDAL process while providing additional nutrients such as nitrogen and phosphorus form the wastewater

Variation in kikuyu grass yield in response to irrigation with secondary and advanced treated wastewaters

Treated wastewater, also called as recycled water, is a reliable source of water for various non-potable purposes. One of the most common uses of recycled water has been for irrigation. A soil column study was carried out for a period of one year. The objective of this study was to determine the effect of irrigation using two different types of treated wastewaters on kikuyu grass (Pennisetum clandestinum) production in the absence of any kind of chemical fertilisers. Soil irrigated with secondary treated wastewater, MBR (Membrane Bioreactor), resulted in highest annual grass production (16,241 kg of dry-matter per hectare (kg DM/ha)) compared to advanced treated wastewater, IDAL (Intermittently Decanted Aerated Lagoon), and tap water (TW) with annual yields of 7028 and 14,216 kg DM/ha, respectively. Irrigation waters, soil extracted waters and soil samples from different depths of the columns were analysed. Sodium adsorption ratio (SAR), exchangeable cations, electrical conductivity (EC) and pH changed in each experimental column due to different characteristics of applied irrigation waters. The results indicate that high contents of nitrogen and phosphorous in MBR water compensated for the presence of moderate salinity level that contributed to the higher production of grass compared to other two types of irrigation waters. The increase in pH from initial amount of 5.9 to 7.3 in top part of IDAL-irrigated soil may have resulted in low grass yield. This pH increase can be attributed to the high concentrations of cations in the irrigation water in the lack of sufficient amount of nitrogen. Overall, the study demonstrated that a relatively higher grass yield in the absence of any types of fertilisers is possible with recycled water irrigation using secondary treated wastewater. Further, the recycled water irrigation with advanced treatment of wastewater, while costs more, does not result in increased yield benefits

Growing lettuce and cucumber in a hydroponic system using food waste derived organic liquid fertiliser

Increased food waste (FW) production and resulting greenhouse gas production due to current disposal methods have promoted the need for recycling. This study describes an innovative method of recovering the nutrients from FW for use in hydroponic systems. The study evaluates the feasibility of using food waste-derived organic liquid fertiliser (FoodLift) for hydroponically producing lettuce and cucumber. The yield obtained using FoodLift was compared with that obtained using commercial liquid fertiliser (CLF). Growing cycles of lettuce and cucumber were completed in 42 and 119 days, respectively. In the case of lettuce, all parameters (such as fresh matter (FM) and dry matter (DM) yields) were similar for the plants grown using FoodLift and CLF. The average FM yields in the hydroponic system grown using FoodLift and CLF were 156 and 161 g/plant, respectively. Statistically insignificant differences (p > 0.05) between the two fertilisers indicate that FoodLift is as effective as CLF in growing hydroponic lettuce. However, the FM and DM yields of cucumber plants grown using FoodLift were significantly lower than those obtained using CLF. This may be attributed to lower phosphorus concentrations (about 2.5 times less) in the FoodLift feed solution during the cucumber plants flowering stage. This was associated with the significant abortion of flowers observed in the cucumber plants fed with FoodLift. Therefore, it is feasible to increase the yield through phosphorus addition into FoodLift to bring its phosphorus concentration at par with CLF. This study demonstrates the potential for applying circular economy principles for managing food waste

Creating livable subdivisions using stormwater, recycled water and groundwater

Integration of green infrastructure (comprising urban lakes, wetlands and parklands) within an urban centre subdivision can significantly improve its livability. Stormwater generated within the urban centre, which is often considered as water carrying significant amounts of pollutants, can be used to create green infrastructure within the subdivision. In addition, recently, “sewer mining” is being used to supplement the non-potable water for urban centres. This source of recycled water is primarily used to satisfy the water required to maintain healthy green infrastructure. Extensive research conducted in recent years have also led to the plan of utilizing constructed lakes and wetlands, as part of green infrastructures, for storing and improving stormwater quality. Furthermore, they serve as significant water features within an urban centre increasing property values. In this work, we present a case study of a local government area (LGA) in Western Sydney, to provide some insights on how using urban lakes (which besides serving as stormwater purifying system) can greatly add to recreational value to a subdivision. City Councils in Western Sydney have successfully created parklands and physical exercise amenities around these constructed wetlands and lakes. These areas attract a large number of visitors throughout the year. The beneficial value of the urban lakes is demonstrated by the increasing values of the properties which are located around these lakes. We conclude that by employing best practices for managing stormwater runoff provide both socioeconomic and environmental benefits to urban centres, and cansignificantly increase the economic value of the region