Evaluation of Non-Conventional Biological and Molecular Parameters as Potential Indicators of Quality and Functionality of Urban Biosolids Used as Organic Amendments of Agricultural Soils

Abstract

Biosolids are waste from wastewater treatment and have a high content of organic matter and nutrients. In this study, not conventional physicochemical and biological properties of biosolids produced during different seasons of the year were evaluated. These properties are not considered in environmental regulations; however, they are of agronomic interest as indicators of quality and functionality in soils. Also, molecular analysis by Fourier-transform infrared (FTIR) was conducted, enzymatic analysis using the APIZYM® system was performed and two indices of functional and microbial diversity were established. The results showed that the biosolids had a high content of total organic carbon, total nitrogen, P, and K. FTIR analyses showed that chemical composition of biosolids was similar during all year. The C and N of microbial biomass demonstrated presence of active microorganisms, as well as a uniformity in its richness and abundance of species that could present a positive synergy with soil microorganisms. The enzymatic activities showed that the biosolids contained an enzymatic machinery available to promote the mineralisation of the organic matter of biosolids and could even transcend into the soil. Finally, biological properties can be used as indicators of quality and functionality of biosolids before being used as an organic amendment, especially in agricultural soils.

Development of a Soil Quality Index for Soils under Different Agricultural Management Conditions in the Central Lowlands of Mexico: Physicochemical, Biological and Ecophysiological Indicators

“…However, the SEI index developed in this study-in addition to using the concentrations of enzyme activities from the API ZYM ® system-included the enzyme activities of dehydrogenase (DHA), urease (UA), and fluorescein diacetate (FDA) (Equation 2). The API ZYM ® system has proven to be a fast and useful tool in establishing profiles of point or space-time "fingerprint" enzymatic activities in complex environmental matrices, such as soils, compost, vermicompost, activated sludge, biosolids, and sediments [41,42,46,48,[50][51][52].…”

Compost Quality Indexes (CQIs) of Biosolids Using Physicochemical, Biological and Ecophysiological Indicators: C and N Mineralization Dynamics

“…In addition to the evaluation of individual enzyme activities, an index called synthetic enzyme index (SEI) [5,33] was developed, reflecting the overall enzyme activity in the composting systems. The SEI included the enzymatic activities of DA, UA and FDA, reported in nmol kg −1 compost h −1 .…”

“…Most of the BS produced in Mexico is disposed of in landfills. However, BS is characterized by a composition rich in nutrients and organic matter (OM) [5]. These BS can be used as organic amendments for the remediation of degraded soils or as organic fertilizers for agricultural soils, improving their physical, chemical and biological properties [6].…”

“…Improved soil conditions have been reported following the addition of BS, through improved water holding capacity (WHC) and improved soil structure, as well as increased fertility from the addition of easily degradable C and N compounds [7]. The addition of BS to degraded soils increases plant cover, microbial activity and diversity, which are stimulated by the addition of easily degradable OM, allowing better nutrient cycling in the soil [5,[8][9][10].…”

C and N Mineralization Dynamics in Composts: Prediction of Soluble Organic Carbon by Multiple Nonlinear Regression

“…En relación con el desempeño obtenido por el modelo de regresión no lineal (r 2 ) del presente estudio, el coeficiente de correlación se encontró dentro del rango obtenidos por los estudios deOliveira et al, 2018 y Ebrahimi et al, 2021 antes mencionados. La correlación baja mostrada por el modelo pudiera deberse a la complejidad en cuanto a la composición de fuentes de C y N de los biosólidos(Medina-Herrera et al, 2020) y estiércol del sistema analizado, a la vez, que se sugiere el análisis de más indicadores que pudieran explicar el comportamiento del indicador COS durante el proceso de compostaje respecto al tiempo.…”