Biosolids Soil Research Articles

Techno-economic analysis of a circular microalgal approach for enhanced wastewater treatment and resource recovery in Northern Portugal

Microalgae culturing in municipal wastewater treatment plants (WWTP) can be a solution to lower the effluent's nitrogen and phosphorus concentrations to comply with the new legislative limits. Microalgae can also promote a circular approach to WWTP by recycling material streams and reducing the energetic consumption of the treatment process. This study aims to perform a techno-economic assessment of the integration of microalgae culture (Chlorella vulgaris) as tertiary treatment at a WWTP in northern Portugal. This evaluation took into account information collected from the specific WWTP under study as well as relevant literature for each stage of the process. The major system flows: (i) a 7377 m3 d−1 treated water flow (ii) the treatment of 107,736 kg d −1 of sludge; (iii) a biosolids soil amendment production of 7580 kg d−1; and (iv) 10,874 kW h d−1 energy for self-consumption. In this work, the integration of microalgae in WWTP achieved yearly gross earnings of approximately 619,100 €.

Greenhouse gas emissions from decomposition of biosolids as affected by stabilization method and soil moisture

AbstractComputational models are useful to estimate agricultural greenhouse gas emissions at regional scales. However, empirically based parameter values are required for the models to accurately represent carbon (C) and nitrogen (N) mineralization rates of different organic amendments in more and less humid regions or during wet and dry periods of the growing season. A controlled environment study was conducted to assess the rates of C and N mineralization in differently processed sewage sludge (biosolids) in wet and dry soil. Parameter values were estimated for use in modelling the degradation of three types of biosolids. A loam soil with either 49% water‐filled pore space (WFPS) or 29% WFPS was amended with mesophilic anaerobically digested (digested), alkaline‐stabilized, or composted biosolids. Headspace samples were collected and analysed for carbon dioxide (CO2) and nitrous oxide (N2O), and soil samples for nitrate () and ammonium (). Four different first‐order models were fitted to the cumulative CO2–C and N2O–N data (R2 > 0.98), and soil (R2 > 0.65) and (R2 > 0.93) concentrations. CO2–C data indicated that C mineralization was higher in soil with 49% WFPS than in soils with 29% WFPS. Seventy‐nine percent of the C compounds in digested biosolids degraded in soil with 49% WFPS, compared with 52% for alkaline‐stabilized biosolids and 8% for composted biosolids. The fitted coefficient values were similar for all of the four first‐order models used in this study and provide useful information for parameterizing more sophisticated mechanistic models of the degradation of biosolids in soil.

Part A: Sanitization and use of sewage sludge in soil Technical Note 2 - Legislation aspects

The use of sewage sludge in soil is a environmentally sustainable practice, compatible with the Brazilian Policy of Solid Wastes. Due to its content of organic compounds and nutrients, the sludge is beneficial to the physical, chemical and biological soil properties and to the development of plants. However, since it may contain chemical and microbiological pollutants, it has to be carefully used by following criteria and procedures concerning the protection of the environment and public health. In 2020, Brazil approved Resolution 498 of CONAMA for the definition of criteria and procedures for production and application of biosolids in soil. Besides its agricultural use, this Resolution covers other uses, such as the recuperation of degraded areas. For the use of sludge on land, it needs to be processed in a Sludge Management Unit licensed by a local environmental agency. Depending on the criteria in the Resolution, biosolids are classified under Classes A and B for their microbiological quality, and under Classes 1 and 2 for their chemical aspects.

Creating topsoils and soil conditioners from biosolids and urban residuals.

A study was conducted to test the suitability of a range of organic and inorganic residuals mixed with municipal biosolids to create a soil amendment effective for a broad range of end uses. Biosolids suitable for unrestricted use were sourced from San Francisco, CA. Residuals including urban wood and yard waste, nut shells, biochar, and sawdust were sourced from nearby producers. Existing biosolids based soil products, peat, and a yard-food compost were used as controls. Experimental mixtures were tested for a range of soil properties, appearance, odor, germination, and growth response. Several mixtures performed as well as or better than the yard-food compost, and several performed comparably to the biosolids soil controls. Yard waste fines blended with biosolids in a 50:50 ratio by volume or yard waste fines blended with biosolids and 20% sand at 40:40:20 were highly effective across all measured indices. Mixed yard and recycled lumber fines blended with biosolids at these same ratios performed similarly well. Blends with a high percentage of char performed poorly in germination and growth response, likely as a result of elevated electrical conductivity. Certain blends such as gypsum and redwood shavings failed to mix well with biosolids to create a uniform looking material and were less visually appealing. In general, blends that met established quality control parameters for compost performed well on the measured indices. These results suggest that blending Class A biosolids with organic and inorganic feedstocks to meet quality criteria developed for compost will create marketable soil products.

Can an amino sugar test estimate potentially available nitrogen from biosolids?

AbstractBiosolids land application is governed by N content and estimates of potentially available N (PAN). Amino sugar test N (AST‐N) has been used with varying success to estimate soil responsiveness to N and optimum N rates. We investigated the utility of an amino sugar test (AST) in estimating PAN and hypothesized that this would depend on biosolids type, rate, and receiving soil. In vitro, we applied three dissimilar biosolids at five rates to four representative southeastern US soils, measured AST‐N, and estimated recovery of biosolids AST‐N. Target PAN rates were zero to two times a realistic yield expectation rate (127 kg N ha−1) for a common biosolids‐receiving grass. Rates were based on biosolids type, total N, and book‐value availability coefficients. Biosolids AST‐N varied from 263 to 9790 mg kg−1 (3.8–20.1% of total N). Soil AST‐N was 66–93 mg kg−1 and differed among soils. Treatment interactions indicated that AST‐N of the biosolids–soil mixtures differed from what might be predicted from biosolids and soil AST‐N and rate. Rate response was linear; thus, the AST did not saturate at the rates tested. Biosolids AST‐N recovery ranged from −303 to 152% depending on biosolids, rate, soil, and their interactions. The AST‐N was related linearly to total N from anaerobic incubation (R2 = 0.10–0.67), depending on biosolids. The weakness of these relationships; the biosolids, rate, and soil interactions; and the potential confounding effects of biosolids and soil NH4–N suggest that AST‐N would not be a good estimator of PAN.

Getting to the root of the matter: Water-soluble and volatile components in thermally-treated biosolids and biochar differentially regulate maize (Zea mays) seedling growth.

The use of thermally treated biomass, including biochar, as soil amendments can improve soil fertility by providing nutrients, stable C and improving soil water-holding capacity. However, if the degree of carbonization is low, these soil amendments can lower crop productivity as a result of high salinity or organic compounds. The overall effect of these soil amendments is mediated by complex relationships between production conditions, soil properties and environmental conditions. This study aimed to 1) characterize the physiochemical properties and organic compounds released by three soil amendments (softwood biochar or pyrogenic carbonaceous biosolids), 2) determine the effects of these amendments on maize (Zea mays) seedling productivity, and 3) relate properties of these amendments to effects on maize seedling productivity under controlled environment conditions. Physicochemical properties and mobile organic compounds (water-soluble and volatile organic compounds were determined. The amendments were tested in maize germination and greenhouse experiments. Chemical fingerprinting of volatile and water-soluble compounds revealed over 100 mobile organic species. Increasing treatment temperature from 270 to 320°C reduces phytotoxicity of pyrogenic carbonaceous biosolids soil amendments. Water-soluble components of pyrogenic carbonaceous biosolids produced at 270°C (inorganic N, Na and/or organic compounds) were associated with reduced maize seedling productivity. Volatile components of pyrogenic carbonaceous biosolids produced at 320°C were associated with improved maize seedling productivity; nitrogen uptake was increased in spite of smaller root systems as a result of increased mineralization of soil or amendment N and/or uptake of organic N compounds. These results suggest that pyrogenic carbonaceous biosolids have potential benefits to provide plant nutrients when the amount of organic and inorganic species are limited during early growth stages, under greenhouse conditions. Future studies should examine these effects under field conditions to confirm whether controlled environment results translate into effects on yield.

Biosolids and conservation tillage: Impacts on soil fungal communities in dryland wheat-fallow cropping systems

Organic amendments and conservation tillage are important management tools for reducing soil erosion and improving soil health in agricultural systems, yet the impacts of these practices on soil microbial communities is poorly understood. We evaluated the effects of biosolid amendments and conservation tillage on soil fungal communities in a dryland wheat (Triticum aestivum L.) –summer fallow cropping system in the inland Pacific Northwest, USA (PNW). Biosolids or synthetic fertilizer was used in combination with conventional (disk) or conservation (undercutter) tillage. Fungal communities were characterized from soil and biosolid aggregates after the second application of biosolids in 2015 and before and after the second application of biosolids in 2016 using high-throughput amplicon sequencing. Biosolid amendments substantially altered fungal community composition, but not diversity, relative to synthetic fertilizer. In contrast, although many more fungal taxa were influenced by conservation tillage when synthetic fertilizer was applied, conservation tillage had relatively little effect on soil fungal communities receiving biosolids, suggesting that the form of N supplied (mineral or organic) may mediate the effects of increasing surface crop residue on fungal communities. Biosolid-mediated shifts in fungal communities were correlated with differences in soil characteristics, especially C, N, and P, and were persistent for at least three years after the initial biosolid application. A small number of taxa, including Fusarium, Ulocladium, Gymnoascus, Mortierella, and Neurospora, were highly enriched by biosolids in soil and dominated fungal communities of biosolid aggregates. Results show biosolids can have strong and lasting impacts on soil fungal communities, likely due to their effects on soil nutrients, and select for a small number of fungi capable of utilizing biosolids as a food source.

Mānuka (Leptospermum scoparium) roots forage biosolids in low fertility soil

Potentially, biosolids could be applied to low fertility or degraded soils to establish mānuka (Leptospermum scoparium), an economically important plant species used for honey and essential oil production. Given that this pioneering species is adapted to low-fertility soils, it is unclear whether it would respond positively to biosolids. We aimed to determine the growth, root morphology and elemental uptake of L. scoparium in contrasting soils amended with biosolids, distributed either homogeneously or heterogeneously. Pot and rhizobox experiments revealed that the roots of L. scoparium morphologically foraged patches of biosolids in soil. This finding is in contrast to previous reports that foraging is uncommon in plants adapted to low fertility soils. In a low-fertility sand, biosolids increased the growth 40-fold, irrespective of the distribution of biosolids. This increase was lower (60%) in an orthic brown soil. In the biosolids-amended soils, the foliar concentrations of N, P, K, S, Mg and Ca were above 2%, 1.5gkg−1, 0.8%, 2.0gkg−1, 1.7mgkg−1 and 0.8% respectively, which is within the range of concentrations found in native species in their natural habitat. In the control soils, foliar concentrations of N, P & S were significantly lower, indicating that these elements may be limiting. The maximum concentration of Mn (660mgkg−1), Zn (211mgkg−1), and Cd (1.5mgkg−1) in leaves of plants growing in biosolids-amended soil should not cause concern to plant health, but it should be taken into account for their potential effect on trophic networks. Further experiments should focus on the design of field-scale applications of biosolids for improving L. scoparium growth and determine the effect of biosolids distribution on nutrient losses.

ChemInform Abstract: Application of Wastewater and Biosolids in Soil: Occurrence and Fate of Emerging Contaminants

AbstractReview: 96 refs.

Application of Wastewater and Biosolids in Soil: Occurrence and Fate of Emerging Contaminants

Wastewater (WW) for irrigation and application of biosolids in soil is becoming important as it is going to become very common in the near future. By 2050, the world is going to have four billion people living in water-scarce countries, making it a norm of freshwater for the cities and WW for agriculture. Further, biosolids might still be used as green biofertilizers for soils, if they are improved from an ecological point of view. However, application of biosolids in soil is argued because of the amount of organic pollutants that compromise the dynamic equilibrium of the biological systems. Therefore, information on the concentration, behavior, and cycling of organic pollutants as well as their possible degradation pathways is needed to predict, prevent, and remediate these pollutants from different sources including WW and biosolids. Among the group of organic pollutants, emerging contaminants (ECs) enter into the soil with the irrigation water from treated effluents and fertilization by biosolids. Quantification of ECs from WW and biosolids is of main importance to predict the toxic effects of WW effluents and sludge. Moreover, their incorporation into vegetables through irrigation and their magnification through natural food webs have been proved and must be monitored. This review presents information on the different sources of emerging contaminants and linking with the ecological effects they produced by reacting in the environment during various applications of WW and biosolids in soil. The available methods for analysis and quantification of ECs in different matrices, such as WW and biosolids, are also presented.

Relationship between Mineral Soil Surface Area and the Biological Degradation of Biosolids Added to Soil

Geochemical and biological processes that operate in the soil matrix and on the soil surface are important to the degradation of biosolids in soil. Due to the large surface area of soils it is assumed that the microbial ecology is associated with mineral soil surface area. The total mineral surface areas were determined for soils from eight different fields selected from a long term study (1972–2006) of annual biosolids application to 41 fields in central Illinois varying in size from 3.6 to 66 ha. The surface areas for the soils varied from 1 to 9 m2/g of soil. The biological degradation rates for the eight soils were determined using a biological degradation rate model (DRM) and varied from 0.02 to 0.20/year−1. Regression analysis revealed that the degradation rate was positively associated with mineral soil surface area (1 m2/g produces 0.018 year−1 increase in the degradation rate). The annual soil sequestration rate was calculated to increase from 1% to 6% when the soil total surface area increased from 1 to 9 m2/g of soil. Therefore, land application of biosolids is an effective way to enhance carbon sequestration in soils and reduce greenhouse gas emissions.

Interactions of triclosan, gemfibrozil and galaxolide with biosolid-amended soils: Effects of the level and nature of soil organic matter

Triclosan, gemfibrozil and galaxolide, representing acidic and non-ionized hydrophobic organic compounds, are biologically active and can be accumulated during wastewater treatment in sewage sludge. The interactions of these substances with the soils amended by sewage sludge-originating biosolids may control their environmental fate. Therefore, the sorption of three organic compounds was studied in dune sand, loess soil, clay soil and mixtures of these media with three different sewage sludge-originating biosolids that were incubated under aerobic conditions for 6months. For each compound, 15 sorption isotherms were produced at pH 7.8–8.0. The sorption of triclosan and gemfibrozil on sand-containing sorbents was examined also under acidic conditions. In some soil series, the compound’s Freundlich constants (KF) are linearly related to the soil organic carbon (OC) content. Notably, for a given OC content, the sand-containing sorbents tend to demonstrate enhanced interactions with triclosan and galaxolide. This may be related with more hydrophobic and/or less rigid soil organic matter (SOM) as compared with the clay-containing soils, implying indirect effects of minerals. Generally the OC-normalized KF vary among different soil–biosolid combinations which is explained by the differences in the composition and properties of SOM, and is also contributed by the non-zero intercepts of the linear KF upon soil OC dependencies. The negative intercepts suggest that below a certain OC level no considerable organic compound–soil interactions would occur. Interactions of molecular and anionic forms of triclosan with a sand-containing sorbent may be comparable, but interactions involving gemfibrozil molecules could be stronger than interactions involving its anion.

Potential for Recycling Nutrients from Biosolids Amended with Clay and Lime in Coarse-Textured Water Repellence, Acidic Soils of Western Australia

Application of biosolids in soils is an efficient method of recycling nutrients from biosolids and it is considered even safer when it is modified after mixing and diluting with other suitable soil organic amendments. A variety of soil organic amendments, such as green manures and composts, are used for modifying and co-composting with biosolids. However, these may not be considered as appropriate biosolids disposal and remedial measures for soils with unique problems such as low soil pH, water repellence nature, and poor water and nutrient retention capacities due to soil textural issues. Historically, soil amendments such as lime, clay, and recently biochar are being applied for such problematic soils at Western Australia and these researches focused mostly on improvement in soil physical and chemical properties. However, studies with potential for applying modified biosolids with these amendments are not complete yet. This review focused on identifying such gaps in these studies from over 170 peer-reviewed key research and review articles published over decades to latest in these areas.

Biosolids Soil Application: Agronomic and Environmental Implications 2014

Biosolids Soil Application: Agronomic and Environmental Implications 2014

New biomimetic approach to determine the bioavailability of triclosan in soils and its validation with the wheat plant uptake bioassay

A new biomimetic approach for triclosan (TCS) was developed based on the leaching of the analyte from different biosolid-amended agricultural soils and the subsequent extraction of the leachates, using a rotating disk sorptive extraction (RDSE) procedure. The leaching equilibrium for TCS was reached at 3h when the ISO method (ISO/TS 21268-1:2007) was followed.The concentrations determined by this biomimetic method were compared with the bioavailability of TCS, determined by its accumulation in the roots of wheat plants grown in the same soil–biosolid systems.It was observed that the amount of organic matter in the soil matrix was a determining factor for mobilization of TCS. An increasing biosolid rate applied to soils resulted in a reduced mobility of TCS because the high amount of organic matter provided by the biosolid increased the hydrophobic interaction between TCS and the matrix. Similarly, increasing biosolid concentrations in the soil significantly decreased the bioavailability of TCS to the wheat plant. Thus, the bioavailability factor in wheat roots decreased from 0.22 to 0.08 for a soil having a pH of 8.2, when the biosolid rate was increased from 30 to 200Mgha−1, respectively.A significant correlation (R=0.98) was obtained between TCS concentration in wheat plants and the proposed biomimetic methodology, indicating that the latter can predict the bioavailability in a time period as short as 180min.The results of this study confirm our previous findings that amending soils with biosolids is beneficial for immobilizing low polarity contaminants and helps prevent their percolation through the soil profile and into groundwater.

Loss and in situ production of perfluoroalkyl chemicals in outdoor biosolids–soil mesocosms

An outdoor mesocosm study was conducted in Baltimore, Maryland, to explore the fate of thirteen perfluoroalkyl substances (PFASs) over the course of three years in biosolids/soil mixtures (1:2) exposed to ambient outdoor conditions. Analysis by liquid chromatography tandem mass spectrometry showed perfluorooctanoate (PFOA) to be the most abundant analyte found early in the soil weathering experiment at 24.1ng/g dry weight (dw), followed by perfluoroundecanoate (PFUnDA) and perfluorodecanoate (PFDA) at 18.4 and 17.4ng/g dw, respectively. Short-chain perfluorinated carboxylates (PFCAs; C4–C8) showed observable loss from biosolids/soil mixtures, with experimentally determined first-order half-lives in soil ranging from 385 to 866 days. Perfluorooctane sulfonate (PFOS), perfluorononaoate (PFNA) and PFUnDA levels in biosolids/soil mixtures remained stable, while other long-chain PFCAs [PFDA, perfluorododecanoate (PFDoDA)] and perfluorooctane sulfonamide (PFOSA) levels increased over time, presumably due to the breakdown of unidentified precursors in a process analogous to that reported previously for wastewater treatment plants. This study informs risk assessment initiatives by furnishing data on the environmental persistence of PFASs while also constituting the first report on in situ production of long-chained PFASs in terrestrial environments.

Soil Carbon Sequestration Resulting from Biosolids Application

Carbon (C) sequestration in soils through the increase of the soil organic carbon (SOC) pool has generated broad interest to mitigate the effects of climate change. Biosolids soil application may represent a persistent increase in the SOC pool. While a vast literature is available on the value of biosolids as a soil conditioner or nutrient source in agricultural systems, there is still limited knowledge on soil sequestration mechanisms of biosolids-borne C or the main factors influencing this capacity. The emerging challenges posed by global environmental changes and the stringent needs to enhance C storage call for more research on the potential of soil biosolids incorporation as a sustainable C storage practice. This review addresses the potential of C sequestration of agricultural soils and opencast mines amended with biosolids and its biological regulation.

Biosolids Soil Application: Agronomic and Environmental Implications 2013

1Catedra de Quimica General e Inorganica, Department of Natural Resources and Environment, School of Agriculture, University of Buenos Aires, Avenida San Martin 4453, C1417DSE Buenos Aires, Argentina 2University of Brasilia, Caixa Postal 04.401, 70910-970 Braśilia, DF, Brazil 3Department of Plant, Soil and Environmental Sciences, University of Florence, Piazzale delle Cascine 28, 50144 Florence, Italy 4Centro de Estudios Ambientales del Mediterraneo (CEAM), C/Charles R. Darwin 14, Parque Tecnologico, 46980 Paterna, Spain 5Department of Biology, Tula State University, Lenin Avenue 92, Tula 300012, Russia

Fate of nickel in a lime-stabilized biosolid, a calcareous soil and soil–biosolid mixtures

Soil contamination with anthropogenic metals resulting from biosolid application is widespread around the world. To better predict the environmental fate and mobility of contaminants, it is critical to study the capacity of biosolid-amended soils to retain and release metals. In this paper, nickel adsorption onto a calcareous soil, a lime-stabilized biosolid, and soil-biosolid mixtures (30, 75, and 150 t biosolid/ha) was studied in batch experiments. Sorption experiments showed that (1) Ni adsorption was higher onto the biosolid than the calcareous soil, and (2) biosolid acted as an adsorbent in the biosolid-soil mixtures by increasing Ni retention capacity. The sorption tests were complemented with the estimation of Ni adsorption reversibility by successive applications of extraction solutions with water, calcium (100 mg/L), and oxalic acid (equivalent to 100 mg carbon/L). It has been shown that Ni desorption rates in soil and biosolid-amended soils were lower than 30 % whatever the chemical reagent, indicating that Ni was strongly adsorbed on the different systems. This adsorption/desorption hysteresis effect was particularly significant at the highest biosolid concentration (150 t/ha). Finally, an adsorption empirical model was used to estimate the maximum permissible biosolid application rate using French national guideline. It has been shown that desorption effects should be quantitatively considered to estimate relevant biosolid loadings.

Study of the Organic Fraction in Biosolids

Biosolids are commonly used in agriculture in the European Union, especially in the Mediterranean countries. Because biosolids can act both as fertilizer and organic amendment, the application dose is based on the specific composition of the waste product according to the European legislation of sewage sludge. Organic compounds in biosolids are extremely complex depending on the use of flocculants and/or coadjuvants in wastewater treatments, and therefore the classification into labile, nonlabile, humic-like compounds, etc., categories is necessary to elucidate the potential dynamics in the soil–biosolid systems. In addition, long-term studies are needed to evaluate the effects of biosolids on soil properties, especially considering soil organic-matter pools. In this study, more than 390 biosolids samples were collected and analyzed from 80 different wastewater treatment plants in southern Spain, during the period 2001–2008 (accumulated equivalent population > 500,000 inhabitants 200 hm3 of wastewater treated). The biosolids samples were originated by aerobic or anaerobic stabilization using different wastewater treatments (64.46% by prolonged aeration, 29.75% by active sludge, 1.37% from percolator filters, 1.37% from biocylinders, and 3.03% from biodisks). Total organic carbon (TOC), total nitrogen (TN), water-soluble C and N, humic acid–like (HA), and fulvic acid–like (FA) compounds were determined in all the samples and correlated with the scale and type of the wastewater treatment and also with the biosolid stabilization procedure used. Considering all the scenarios, biosolids from low-scale treatment plants, active sludge wastewater system, and aerobically stabilization of biosolids seemed to be the most efficient for mineralization and therefore for agricultural purposes. However, it is also necessary to take into account the potential N volatilization from calcareous amended soils and thus, more research must be done to ascertain the biosolid behavior in agriculture.