Liquid Digestate Filtration with Hydrocyclone for Long Standing Micro-Irrigation System

The success of the use of wastewater in the irrigation depends on a wealth of factors. These include the amount of solids in the wastewater or its filtrate, the ability of the suspended material to form biofilms, the pressure of the water in the system, the type of filters and emitters, and age of the systems. Digestate from crop biomass and manure is increasingly being used, and its liquid fraction was indicated as a potential source for a wastewater irrigation. When used for irrigation purposes, information on the solid particles fractions, mostly salts, of these liquids in the irrigation systems are scarce. In case of low pressure (60 kPa) and low rate emitters (0.9 and 1.4 L h-1 emitter-1), high quality drip tapes showed a reduction of uniformity of distribution by 5.2 % on average depending on the activated sludge used as secondary effluent. In the present work, we studied the role of an increasing ratio between a hydrocyclone-filtered digestate liquid fraction and tap water on the performance of an irrigation system and water quality. Treatments included 3 diluition ratios (10 %, 25 %, and 50 % of total solution used for the irrigation) in contrast to tap water as control and measurements were taken at an hourly basis on an 8-h irrigation cycle, that simulates most of the irrigation cycles occurring in a broad range of crops. Hydrocyclone filtration scarcely affected the traits of the digestate liquid fraction used for the irrigation. Irrigation with hydrocyclone-filtered digestate liquid fraction injected in the system at 10 % and 25 % dilution did not affect the performance of the system nor the traits of the liquid fraction released by the emitters, whereas using 50 % dilution of the HF-DLF consisted in a lower amount of liquid released and of an increasing pH of the dilution.