Responses of Rhizosphere Fungal Communities to the Sewage Sludge Application into the Soil

A review on control and abatement of soil pollution by heavy metals: Emphasis on artificial intelligence in recovery of contaminated soil

"Save Soil Save Earth" is not just a catchphrase; it is a necessity to protect soil ecosystem from the unwanted and unregulated level of xenobiotic contamination. Numerous challenges such as type, lifespan, nature of pollutants and high cost of treatment has been associated with the treatment or remediation of contaminated soil, whether it be either on-site or off-site. Due to the food chain, the health of non-target soil species as well as human health were impacted by soil contaminants, both organic and inorganic. In this review, the use of microbial omics approaches and artificial intelligence or machine learning has been comprehensively explored with recent advancements in order to identify the sources, characterize, quantify, and mitigate soil pollutants from the environment for increased sustainability. This will generate novel insights into methods for soil remediation that will reduce the time and expense of soil treatment.

Microbial Diversity and P Content Changes after the Application of Sewage Sludge and Glyphosate to Soil

Pesticides, despite their side effects, are still being used in almost every agriculture, horticulture, maintaining municipal greenery in urban areas and even in home gardens. They influence human life and health and the functioning of entire ecosystems, including inanimate elements such as water and soil. The aim of the study was the evaluation of the suitability of sewage sludge in improving the quality of soil treated with a non-selective herbicide-glyphosate, applied as Roundup 360 SL. A pot experiment was conducted with the use of two arable soils (MS and OS), which were amended with sewage sludge (SS), glyphosate (GL) and sewage sludge with glyphosate (SS+GL). Soil samples were taken after 24 h, 144 h and 240 h and total phosphorus (TP) content (TP), total number of bacteria/fungi, activity of dehydrogenases (Dha), acidic phosphatase (Acp), alkaline phosphatase (Alp), genetic biodiversity of bacteria/fungi using the terminal restriction fragment length polymorphism method were determined. The application of SS and GL to OS caused an increase in Acp (approximately 35%) and a decrease in Alp activity (approximately 20%). Additionally, GL may influence on an increase in the number of fungi and the decrease in the number of bacteria. In soil with SS+GL increase in the fungal diversity in MS and OS was also observed. Moreover, a positive between TP and the number of bacteria and the activity of phosphatases correlation was reported. The obtained results indicate that analyzed sewage sludge could be potentially applied into soil in in situ scale and could constitute a valuable reclamation material.

On the sustainability of land applications of sewage sludge: How to apply the sewage biosolid in order to improve soil fertility and increase crop yield?

The fertilization using sewage sludge (SS) and/or SS-derived products have been extensively studied and known to increase crop yield as soil nutrients and plant growth are improved. This study aimed to evaluate two SS application methods (i.e. mulching and mixing with the soil) on soil fertility parameters and the productivity of cereal crops. It compared the effect of SS fertilization methods on changes in soil physicochemical parameters in order to highlight the application mode which gives the best agronomic values and sustains soil productivity. Foliar surface, grain starch content and grain yield of durum wheat (Triticum durum) were determined in plants grown in plastic planters for different fertilization treatments (SS-mulched, SS-mixed, urea, and unfertilized). Each SS treatment was applied in three levels (SS1 = 1% w/w ratio, SS2 = 4%, SS3 = 8.3%). The application of SS improved all soil properties compared to the control and urea, with the SS mulching treatment was the best. The significant improvement of soil fertility was confirmed by soil C:P ratio which indicated a good soil mineralization status, in particular under the screen formed by mulching that helped to conserve high soil moisture for optimizing plant growth. Soil calcium accumulated in greater amount in biosolid-soil mixtures than in SS-mulched soils. Regardless of SS doses, the highest crop grain yields were obtained with the SS mulch treatments. Mulching SS, compared to SS-mixed soils, brings better results in terms of improving soil fertility and yielding high productions. The applicable of this method is also easy in the field and/or large-scale cultures.

The impact of sewage sludge on the fungal communities in the rhizosphere and roots of barley and on barley yield

Current problems with sewage sludge (SS) disposal could be solved by application to agricultural land considering its fertilizer properties and ability to improve soil condition. However, SS may contain heavy metals as well as pathogenic microorganisms. In this study, molecular analysis of partial 18S rRNA gene was used to study the impact of SS application into the soil on the genetic diversity of fungal communities, especially arbuscular mycorrhizal fungi in the rhizosphere and roots of barley. These samples were collected on three dates from the control soil without SS and from the soil with the addition of SS at the concentrations of 5 and 15 t ha-1. Fungal alpha diversity in the rhizosphere of barley was affected by SS differently than in barley roots. In addition, principal component analysis and cluster analysis revealed that fungal communities were strongly influenced by the SS addition into the soil, sample type, and the sampling date. This approach was complemented by an evaluation of the basic parameters of barley production and the response of these parameters to the presence of SS in the soil. The plant height increased with increasing SS concentration and the thousand seed weight significantly increased at the concentration of 5 t ha-1 SS but significantly decreased in 15 t ha-1.

Optimal Solutions for the Use of Sewage Sludge on Agricultural Lands

The use of sewage sludge in agriculture decreases the pressure on landfills. In Romania, massive investments have been made in wastewater treatment stations, which have resulted in the accumulation of important quantities of sewage sludge. The presence of these sewage sludges coincides with large areas of degraded agricultural land. The aim of the present article is to identify the best technological combinations meant to solve these problems simultaneously. Adapting the quality and parameters of the sludge to the specificity of the land solves the possible compatibility problems, thus reducing the impact on the environment. The physico-chemical characteristics of the fermented sludge were monitored and optimal solutions for their treatment were suggested so as to allow that the sludge could be used in agriculture according to the characteristics of the soils. The content of heavy metals in the sewage sludge was closely monitored because the use of sewage sludge as a fertilizer does not allow for any increases in the concentrations of these in soils. The article identifies those agricultural areas which are suitable for the use of sludge, as well as ways of correcting some parameters (e.g., pH), which allow the improvement of soil quality and obtained higher agricultural production.

Risk Assessment of Soil Contamination with Heavy Metals from Municipal Sewage Sludge

Sewage sludge (SS) is a by-product of processes conducted during the treatment of wastewater. It can be used in many different ways. One of them is the use of SS in agriculture as an organic fertiliser, but the main criterion for such use is the heavy metals (HMs) content. Knowledge of the total content of HMs in SS does not translate into the danger it may pose. The toxicity of metals is largely dependent on their mobility. The mobility of SS from three different wastewater treatment plants (WWTP) of the Świętokrzyskie Voivodeship, which were characterised by an increased zinc content, was examined in this study. The aim of the study was to prove whether the high level of zinc in SS actually disqualifies the possibility of its natural use. Calculations were made for five environmental hazard indicators: the geoaccumulation index of heavy metals in soil (Igeo), potential environmental risk indicator (PERI), risk assessment code (RAC), environmental risk factor (ERF), and the authors’ own environmental risk determinant (ERD) indicator. The obtained results show how important mobility analysis is when assessing the possibility of natural use of SS.