Sewage sludge treated with bentonite, vermiculite or biochar can improve soil properties and enhance growth of grasses

Abstract

Sewage sludge treated with 15% bentonite, vermiculite or biochar was evaluated as a soil amendment in comparison to limed and untreated sludge. Seven treatments were established to two soils, an acid and an alkaline, in three replications, i.e. 2% addition of sludge treated with bentonite, vermiculite, biochar and lime and application of 2% untreated sludge, inorganic fertilization and no sludge or inorganic fertilizers (control). Then, the soil treatments were used in a pot experiment with perennial ryegrass (Lolium perenne L.) as a test plant. Sludge treated with the clay minerals or biochar improved pH of the acid soil and significantly increased organic matter and available nutrients of both soils compared to control. Although no salinity or sodicity hazard was evidenced, the initial salinity of acid and alkaline soil increased by four‐eight and two‐three times, respectively, upon addition of all sludge treatments, especially that of untreated sludge. Moreover, soil available zinc (Zn) increased by four‐eight times. Soil application of sludge treated with the clay minerals or biochar increased the total aboveground biomass yield of ryegrass in the acid and alkaline soil by 133%–171% and 72%–88%, respectively, compared to control and enhanced nutrient uptake by plants. Furthermore the microbial metabolic quotient indicated lack of low pH and heavy metal stress with addition of sludge to the acid soil. After three harvests of ryegrass, the residual effect of sludge on pH of acid soil and salinity, available phosphorus (P), Zn and boron (B) of both soils still persisted. Thus sewage sludge treated with 15% bentonite, vermiculite or biochar could be applied to soils at a rate of 2% (≈80 Mg ha−1) to serve as soil amendment and fertilizer for grasses and pasture species; however, caution is needed regarding possible P build‐up, Zn phytotoxicity and salinization risks.

Soil Enzyme Response and Calorific Value of Zea mays Used for the Phytoremediation of Soils Contaminated with Diesel Oil

“…Vermiculite is chemically inert, biologically stable, and non-combustible. It has a high sorption capacity and buffering properties [55][56][57][58].…”

“…Vermiculite is also employed as a filtering material in the food industry, a carrier in animal feeds, or a sorbent in environmental protection. Vermiculite's ability to absorb and store a significant amount of water and cations, gradually releasing them, characterizes it as an excellent buffering material influencing the maintenance of optimal soil pH, aeration, and nutrient retention [55][56][57][58]. The vermiculite used in the experiment was purchased from Sobex company (Drezdenko, Poland).…”

“…The interaction of these sorbents in diesel oil-contaminated soil was variable. Vermiculite, as a mineral with high sorption capacity [54,57], mitigated the adverse effects of the petroleum-derived product on the aboveground biomass. This could contribute to creating more favorable conditions for plant growth and influence the increased availability of nutrients.…”

“…This could contribute to creating more favorable conditions for plant growth and influence the increased availability of nutrients. According to studies by Vasilyeva et al [59], Marwa et al [52], Balidakis et al [57], Szadkowski et al [55], and Jafari et al [56], vermiculite may enhance soil aeration and contribute to improved water retention, which is crucial for root growth and development.…”

Functional biochar as sustainable precursors to boost the anaerobic digestion of waste activated sludge from a circular economy perspective: a review

“…Several studies [e.g., (Ruan et al 2023;Li et al 2019;Zhang et al 2019)] have demonstrated that adding functional biochar to AD of WAS can effectively immobilize heavy metals and reduce environmental risks. Athanasios et al (Balidakis et al 2023) further assessed the effectiveness of sludge amended with biochar as a soil amendment. Research has shown that adding biochar significantly improved soil organic matter and fertility.…”