The effects of enriched biochar and zeolite and treated wastewater irrigation on soil fertility and tomato growth

Abstract

Resource recovery from wastewater treatment is the key for sustainable environment management. Treated wastewater (TWW) represents a promising opportunity not only as irrigation water but also as a source of nutrients that can be recovered with adsorbent materials, such as biochar and zeolite. These materials efficiently adsorb phosphate and ammonium, respectively, from wastewater, and once enriched can act as soil fertilizer. This study investigated, the impact of PO43--enriched biochar and NH4+-enriched zeolite, combined or not with treated wastewater (TWW) irrigation, on soil fertility and growth of tomato plants, through a pot experiment. Five treatments were tested: control soil irrigated with tap water, soil amended with enriched biochar and zeolite with tap water or TWW, and soil amended with natural biochar and zeolite with TWW. After 80 days, shoot dry weights of tomato plants showed no significant differences across treatments. However, root dry weights decreased in plants irrigated with TWW, whether unamended or amended with natural biochar and zeolite. The TWW irrigation, both with and without enriched amendments improved soil total N and available P by 22 and 15 %, respectively, but increased soil salinity, as evidenced by 27 % rise in electrical conductivity. However, enriched and natural biochar and zeolite effectively mitigated salinity effect, promoting a more salinity-tolerant microbial community, and increasing microbial biomass carbon. These results support the integrated use of TWW with nutrient-enriched amendments to support the transition to a circular economy in the water sector.