Greywater irrigation and soil quality: An assessment framework adjustment and application
Adi Maimon, Gilboa Arye, Amit Gross
Abstract
The on-site use of greywater (GW) is an increasingly popular practice for alleviating water stress in various parts of the world, particularly as a water source for irrigation. However, GW can contain a range of pathogenic bacteria that may compromise public health as well as substances with the potential to induce environmental consequences such as soil hydrophobicity, accumulation of salts, and damage to plants. Whereas health issues are being addressed by GW legislation, environmental risks are largely ignored. Therefore, the main objective of the current study was to quantify the impact of GW irrigation on soils by developing a soil quality index (SQI) using a 14-month planter experiment. The sum of the absolute value of all indicator scores represents the final score of the integrated SQI which ranged from 0 to 100. Three threshold values were identified where <30 represents deteriorated soil quality, 50-70 is intermediate quality, and >70 is optimal quality. The results for the planter experiment revealed that after 14 months, the SQI of all raw GW irrigated soil were lower than 70 which indicates soil functions and plant health might be compromised. The use of scoring functions was found to be a useful tool for quantifying and comparing the effect of GW irrigation on different soil quality indicators. Integration of all indicator scores into a single SQI quantifies and summarizes the overall beneficial and detrimental effects of GW irrigation. However, for better understanding and management decisions SQI scores should be used and interpreted in conjunction with the scores of the single indicators constituting this index. It has been concluded that irrigation with raw GW might compromise soil quality and thus its treatment prior to use is highly recommended. However, treated GW has not compromised soil quality even after 14 months of irrigation.