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

A review of the influence of heat drying, alkaline treatment, and composting on biosolids characteristics and their impacts on nitrogen dynamics in biosolids-amended soils

Application of biosolids to agricultural land has gained increasing attention due to their rich nutrient content. There are a variety of treatment processes for converting sewage sludge to biosolids. Different treatment processes can change the physicochemical properties of the raw sewage sludge and affect the dynamics of nutrient release in biosolids-amended soils. This paper reviews heat drying, alkaline treatment, and composting as biosolids treatment processes and discusses the effects of these treatments on biosolid nitrogen (N) content and availability. Most N in the biosolids remain in organic forms, regardless of biosolids treatment type but considerable variation exists in the mean values of total N and mineralizable N across different types of biosolids. The highest mean total N content was recorded in heat-dried biosolids (HDB) (4.92%), followed by composted biosolids (CB) (2.25%) and alkaline-treated biosolids (ATB) (2.14%). The mean mineralizable N value was similar between HDB and ATB, with a broader range of mineralizable N in ATB. The lowest N availability was observed in CB. Although many models have been extensively studied for predicting potential N mineralization in soils amended with organic amendments, limited research has attempted to model soil N mineralization following biosolids application. With biosolids being a popular, economical, and eco-friendly alternative to chemical N-fertilizers, understanding biosolids treatment effects on biosolids properties is important for developing a sound biosolids management system. Moreover, modeling N mineralization in biosolids-amended soils is essential for the adoption of sustainable farming practices that maximize the agronomic value of all types of biosolids.

Structural analysis and characterization of biosolids. A case study of biosolids from wastewater treatment plants in Western Greece

The great interest of modern societies in the reuse of wastes opens up new horizons in the field of wastewater, as well. In particular, the treated sludge resulting from a Wastewater Treatment Plant (WWTP) is dealed with a new perspective in the context of circular economy. The aim of this study is the characterization of its complex matrix, and the evaluation for reuse. Biosolids (BS) collected from four urban WWTPs in the Western region of Greece i.e. Agrinio (AG), Amaliada (AM), Aegio (AE) and Itea (IT). Analytical and spectroscopical methods namely TGA, ICP-OES, Fluorescence, SEM/EDS, XRD, FT-IR and NMR were the means that served this purpose. SEM along with XRD proved the amorphous nature of BS. The dominant metals detected in the samples are: Fe, Zn, Mn, with concentrations which meet the guidelines included in 86/278/EEC Directive. The inorganic load is of great importance, along with their humic acid content, adding value at the samples as fertilizers. BS appeared to be rich in organic matter with long aliphatic chains and numerous functional groups, as capturedin FT-IR spectra. The applied methods form an analytical protocol of the BS mapping, highlighting its potential as a material to be utilized in agriculture.

New Trends in Environmental Engineering, Agriculture, Food Production, and Analysis

Modern agriculture and aquaculture, as well as related food processing, are associated with a significant use of environmental resources and a growing impact on the natural environment [...]

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

The Bajío—Mexico’s central lowlands—is a region of economic importance because of its agricultural industry. Over time, agricultural practices have led to soil deterioration, loss of fertility, and abandonment. In this study, six agricultural soils were analyzed: AGQ, CTH, CTJ, JRM, CRC, and CYI, and used to develop a soil quality index (SQI) that includes the use of physicochemical, biological, and ecophysiological indicators to differentiate soil quality. Principal component analysis (PCA) was used, reducing the indicators from 46 to 4, which represents 80.4% of data variability. It was implemented the equation of additive weights using the variance of the principal components as a weight factor for the SQI. The developed SQI was according to the indicators WHC, SLT, N-NO3−, and qCO2, differentiating the quality of soils from the agricultural management in low quality (JRM < CYI < AGQ) and moderate quality (CTJ < CRC < CTH). The use of biological and ecophysiological indicators added to the PCA and the equation of additive weights allowed establishing an SQI with a minimum of indicators, sensitive to agricultural management, facilitating its interpretation and implementation for the Mexican Bajío region and soils in similar conditions around the world.