Addition Of Biosolids Research Articles

Evaluation of impacts of biosolids application and drainage water management on soil N2O and CH4 emissions using the flux gradient method

Existing studies have shown contradictory findings with respect to whether biosolids applications on agricultural lands lead to intensification of soil greenhouse gas (GHG) emissions. Here, we describe the results of deployment of the micrometeorological flux gradient method to quantify post-biosolid soil emissions of nitrous oxide (N2O) and methane (CH4) on a farm with drainage water management (DWM) on the Eastern Shore of Maryland. The fluxes following biosolid additions to cornfields in 2020 were compared with fluxes from the same farm in 2018, when no fertilizer was applied to soybeans, and in 2019, when urea ammonium nitrate (UAN) was applied to corn. Extractable soil nitrate was highest following biosolids application, contributing to the highest N2O emissions in the growing season of 2020 compared to 2018 (no fertilizer) and 2019 (UAN). Other contributing factors include the low C:N ratio of the biosolids and the above average precipitation in 2020. In contrast, different fertilization regimes did not generate distinct differences for CH4 fluxes, which were very low in all three years. No statistically significant treatment effect of DWM was found for either N2O or CH4 during the peak emission period after biosolids application, which aligns with the result of our earlier research. Annualized estimated N2O emission factors (EFs) for biosolids addition were 5–6 % in the DWM and 3–4 % in the non-DWM fields, although this includes uncertainties associated with gap filling. These biosolids EFs are 2–3 times the N2O EF for synthetic fertilizer application at this same farm in 2019 (1–2.5 %) and 2–4 times the IPCC Tier 1 EF (1.6 %) for synthetic fertilizer, demonstrating the intensification effect of biosolids addition on soil N2O emissions for the cropland studied here.

An Assessment of the Suitability of Contrasting Biosolids for Raising Indigenous Plants in Nurseries

Disposal of biosolids, the solid fraction of sewage treatment, is a global environmental issue. Biosolids contain valuable organic matter and plant nutrients; however, they also contain contaminants including trace elements, xenobiotics, and pathogens. The quality of the biosolids greatly depends on the source of wastewater (i.e., industrial vs. domestic) and the treatment processes. We aimed to determine the potential of three distinct biosolids and one pond sludge to grow indigenous plants for ecosystem restoration. For each amendment, we tested six indigenous species, Veronica salicifolia, Corokia cheesemanii, Griselinia littoralis, Phormium tenax, Poa cita, and Cordyline australis in bark mixed with biosolids and/or pond sludge at rates of 0–50%. There was a significant positive correlation between plant growth and biosolid addition up to a species-dependent plateau. Growth decreased at the highest rates. At a rate of 10% for fresh biosolids and 30% for aged biosolids provided consistent optimal growth across all species. The pond sludge was unsuitable for the establishment of indigenous seedlings. At the optimal rates, there were significant increases in foliar N, P, K, S, and Zn. None of the trace elements accumulated in the plants at phytotoxic concentrations or levels that presented a risk to ecosystems. Future work should determine how plants raised with biosolids perform once planted out in the field.

Influence of Cassava Peels Biosolid Addition on the Technological Properties, Thermal Performance, and Microstructural Characteristics of Fired Clay Bricks

Influence of Cassava Peels Biosolid Addition on the Technological Properties, Thermal Performance, and Microstructural Characteristics of Fired Clay Bricks

Enhancing biogas production in anaerobic digestion of MSW with addition of bio-solids and various moisture sources

This study aimed to investigate the influence of moisture content on the anaerobic digestion of municipal solid waste (MSW) with the addition of leachate, tap water, wastewater, and sewage sludge. To accomplish this, ten sets of batch experiments were conducted to examine the impact of these various moisture sources on the rate of degradation, indicated by cumulative biogas yield, volatile solids (VS) and total solids (TS) removal. The addition of sludge with leachate and wastewater to MSW resulted in biogas yields that were approximately 30 % higher than the biogas yield from MSW and wastewater alone. Based on the observations of VS removal, it was observed that the addition of sludge degraded about half of the substrate. Therefore, it was observed that the addition of 10 % sludge with leachate and wastewater to MSW provides the best outcomes. The lowest biogas yield was observed with the mixing of tap water with MSW. Further, it was determined that the optimal moisture content for MSW degradation should be greater than 75 % of field capacity (FC). The cumulative biogas yield decreased by more than 50 % when the moisture contents decreased from 100 % to 50 % of FC. The reduction in biogas production at low moisture contents is attributed to limited mass transfer, and the hydrolysis rate also slightly decreases with an increase in total solids. The kinetic study was also carried out using the first order, modified Gompertz, Transference, and Logistic models, and the predicted cumulative biogas yield was compared with the experimental data. The modified Gompertz and Logistic models showed the best fit (R2 ≥ 0.994) with the experimental data for all the sets. The sludge, leachate, and wastewater are produced in large quantities in developing countries, and this study may provide a possible utilization strategy of these wastes for accelerated degradation of MSW.

Pulp mill biosolids mitigate soil greenhouse gas emissions from applied urea and improve soil fertility in a hybrid poplar plantation

Pulp mill biosolids (hereafter 'biosolids') could be used as an organic amendment to improve soil fertility and promote crop growth; however, it is unclear how the application of biosolids affects soil greenhouse gas emissions and the mechanisms underlying these effects. Here, we conducted a 2-year field experiment on a 6-year-old hybrid poplar plantation in northern Alberta, Canada, to compare the effects of biosolids, conventional mineral fertilizer (urea), and urea + biosolids on soil CO2, CH4 N2O emissions, as well as soil chemical and microbial properties. We found that the addition of biosolids increased soil CO2 and N2O emissions by 21 and 17%, respectively, while urea addition increased their emissions by 30 and 83%, respectively. However, the addition of urea did not affect soil CO2 emissions when biosolids were also applied. The addition of biosolids and biosolids + urea increased soil dissolved organic carbon (DOC) and microbial biomass C (MBC), while urea addition and biosolids + urea addition increased soil inorganic N, available P and denitrifying enzyme activity (DEA). Furthermore, the CO2 and N2O emissions were positively, while the CH4 emissions were negatively associated with soil DOC, inorganic N, available phosphorus, MBC, microbial biomass N, and DEA. In addition, soil CO2, CH4 and N2O emissions were also strongly associated with soil microbial community composition. We conclude that the application of the combination of biosolids and chemical N fertilizer (urea) could be a beneficial approach for both the disposal and use of pulp mill wastes, by reducing greenhouse gas emissions and improving soil fertility.

Influence of biosolids and sewage effluent application on sitagliptin soil sorption

Biosolids and sewage effluent application to agricultural fields is becoming a win-win practice as both an economical waste management strategy and a source of nutrients and organic matter for plant growth. However, these organic wastes contain a variety of trace chemicals of environmental concern such as pharmaceuticals and personal care products (PPCPs), which may pose a risk to agricultural fields and ecosystems. This work aims to investigate the sorption of sitagliptin on four agricultural soils, evaluate the effects of biosolids and sewage effluent application, and elucidate the main sorption mechanism of the pharmaceutical on soils. The sorption study revealed that the sorption capacities of sitagliptin on different soils were positively related to the contents of soil organic matter and negatively associated with soil pH values. The application of biosolids and sewage effluent decreased the sorption capacity of sitagliptin, which may be attributed to the loading of dissolved organic matter derived from organic wastes. The Freundlich isotherm model demonstrated that the addition of biosolids from 0 to 100 % (W/W) consistently decreased the sorption affinity (Kf) of sitagliptin from 1.69 × 102 to 3.82 × 101 mg(1-n) Ln kg−1. Sewage application at 0, 10, 50, and 100 % (V/V) also reduced the Kf values from 1.69 × 102 to 9.17 × 101 mg(1-n) Ln kg−1. Attenuated Total Reflection (ATR)-Infrared (IR) spectroscopy analyses suggested that electrostatic interactions between carbonyl and amino groups of sitagliptin and the negatively charged soil surface are the main sorption mechanisms. In a co-solute system, the sorption affinity of sitagliptin on the soil decreased with increasing metformin concentrations, suggesting that competitive sorption may reduce the sorption capacity of individual contaminants in soil systems containing multiple PPCPs.

Leaching of phthalate acid esters from plastic mulch films and their degradation in response to UV irradiation and contrasting soil conditions.

Phthalate acid esters (PAEs) are commonly used plastic additives, not chemically bound to the plastic that migrate into surrounding environments, posing a threat to environmental and human health. Dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) are two common PAEs found in agricultural soils, where degradation is attributed to microbial decomposition. Yet the impact of the plastic matrix on PAE degradation rates is poorly understood. Using 14C-labelled DBP and DEHP we show that migration from the plastic matrix into soil represents a key rate limiting step in their bioavailability and subsequent degradation. Incorporating PAEs into plastic film decreased their degradation in soil, DBP (DEHP) from 79% to 21% (9% to <1%), over four months when compared to direct application of PAEs. Mimicking surface soil conditions, we demonstrated that exposure to ultraviolet radiation accelerated PAE mineralisation twofold. Turnover of PAE was promoted by the addition of biosolids, while the presence of plants and other organic residues failed to promote degradation. We conclude that PAEs persist in soil for longer than previously thought due to physical trapping within the plastic matrix, suggesting PAEs released from plastics over very long time periods lead to increasing levels of contamination.

Trace Element Uptake by Willows Used for the Phytoremediation of Biosolids.

The land application of biosolids can result in the unacceptable accumulation of Trace Elements (TEs) in agricultural soil and potentially introduce xenobiotics and pathogens into the food chain. Phytoremediation of biosolids aims to minimize this risk, while producing valuable biomass. Willows, well known to accumulate zinc (Zn), are used extensively in farming systems for soil conservation, shelter and as feed supplements with demonstrable health benefits. Potentially, biosolids phytoremediation could occur on marginal lands adjacent to farmlands where willows are grown for supplementary fodder. We aimed to determine the uptake and distribution of Zn and other TEs in willows grown on soils amended with biosolids and biosolids blended with biochar, with a view to their use as stock fodder. In the Canterbury Region, New Zealand, we grew Salix 'tangaio' (S. matsudana X S. alba) in a greenhouse trial and field study. The biomass production of the willows was unaffected by biosolids and increased by the biosolids+biochar mixture. The addition of 4% biosolids (w/w) to the soil resulted in a foliar Zn concentration of 600-1000 mg kg-1, some 25 times higher than the average New Zealand pasture. Zinc concentrations were highest in the bottom leaves and increased throughout the season. Biosolids addition doubled the copper (Cu) concentration to 10 mg kg-1. Adding biochar to the system reduced the plant uptake of Cu and to a lesser extent Zn, while cadmium (Cd) uptake was unaffected. For Cd, Cu, and Zn, plant uptake was a function of the Ca(NO3)2-extractable concentration, both in greenhouse experiments and the field trial. Future work should determine the changes in plant TE uptake over several growing seasons.

Comparison of methodolgies of soil quality indices (SQI) for sodic soil

Soil degradation and the use of urban biosolid wastes to soil restoration have an economic, social-environmental and health impact. Therefore, there is interest worldwide in the use and comparison of methodologies to establish soil quality indexes (SQIs) based on physical, chemical, and biological indicators of soils. Considering that more than 60% of the territory in the Bajío region of Mexico in the State of Guanajuato is affected by some type of soil degradation, three methodologies for the establishment of SQIs—additive, weighted and unified weighted indexes—were compared in this study to evaluate the short-term effects—30 days—of the addition of biosolids as soil improvers. The methodologies were applied in experiments on carbon (C) and nitrogen (N) mineralization dynamics in a sodic agricultural soil. The ammonium indicator (N-NH4+) was established as the one that is most related to the quality of the soil. The additive and unified weighted indexes differentiated the level of soil quality with respect to time and treatment. The developed SQIs can be used for short-term assessment of the quality of agricultural soils under amendment addition treatments with biosolids or similar organic products.

Short-term amendment of biosolid on agricultural soil: effects on C and N mineralization and microbial activity

Adding biosolids to agricultural soils can improve its quality through increased storage of C and N. A study to analyze the short-term impact of the addition of biosolids on the release of nutrients and the microbial activity in agricultural soil was carried out. The microbial biomass C (MB-C), urease activity (UA), and mineralization of N and C at different application rates of biosolids were evaluated (0 mg, 100mg and 200 mg of N-NH4+ kg-1). In addition, a biosolid-only treatment was tested. It was observed an increase in C and N mineralization, NH3 volatilization, and MB-C content, according to the application rate of biosolids. In biosolid treatments, UA increased 100% on average in the first seven days of incubation. These results suggest that the nutrient content in the soil is improved and microbial activity is positively stimulated.

Immobilization of lead by amendments in a mine-waste impacted soil: Assessing Pb retention with desorption kinetic, sequential extraction and XANES spectroscopy

Chemical stabilization is an in-situ remediation that uses amendments to reduce contaminant availability in polluted soils. Rates of phosphate, lime, biochar, and biosolids were evaluated as affecting Pb speciation and mobility in soil samples of a mining area located in Vazante, state of Minas Gerais, Brazil. Chemical and mineralogical characterization, desorption kinetics, sequential extraction, leaching evaluation in columns and speciation using X-ray absorption near edge structure were performed. Pb adsorbed on bentonite and on anglesite were the predominant species in the unamended soil. The treatments with phosphate and lime transformed part of the Pb species to pyromorphite. Conversely, part of Pb species was transformed to Pb adsorbed on citrate in the soil amended with biochar, while PbCl2 was formed in soil samples amended with biosolids. Phosphate and lime increased the Pb extracted in the residual fraction, thus showing that more recalcitrant species, such as pyromorphite, were formed. Biosolids and biochar treatments decreased the Pb in the residual fraction, and the fraction associated to organic matter increased after the addition of biosolids. Phosphate and lime were effective to immobilize Pb and to decrease Pb desorption kinetics, but the organic amendments increased the desorption kinetics of Pb in all rates applied. The soil amended with phosphate decreased the Pb leached in the experiment with leaching columns.

Use of Biosolids to Enhance Tomato Growth and Tolerance to Fusarium oxysporum f. sp. radicis-lycopersici

The European Green Deal proposes the reuse of any kind of waste that can be safely repurposed; sludge may also be reused as a biosolid. The present research aims to evaluate a biosolid made from sludge, originating from a wastewater treatment plant (WWTP) for its effect on tomato growth and enhancement of tolerance against the phytopathogenic fungus Fusarium oxysporum f. sp. radicis-lycopersici (Forl). Peat and/or two soil types were amended with biosolid (0, 80 and 160 tons/ha) to form substrates on which tomato plants were grown either under controlled conditions, in a growth chamber or outdoors, in a net protected area. Plant growth and disease parameters were recorded 4–7 weeks after application of Forl inoculum in the substrates. Results showed that biosolid addition enhanced plant growth and increased tolerance against tomato foot and root rot caused by Forl. Specifically, fresh weight, root weight, stem height and leaf number of tomato plants in Forl-inoculated soils that had received biosolid, were increased when compared to Forl-inoculated control soils. Forl resulted in higher disease severity on plants grown outdoors in biosolid plus clay soil than in biosolid plus sandy soil, while the opposite occurred under controlled conditions where higher disease index was recorded on plants grown in peat plus sandy soil than in peat plus clay soil. These findings strongly suggest that this biosolid may act as an organic fertilizer and possible stimulant of tomato tolerance against Forl, and the effect is soil type dependent. Therefore, this biosolid should be considered for its possible use in agriculture according to the principles of circular economy and waste minimization. • Biosolid addition enhances tomato growth in different substrates and conditions. • Disease is less severe on plants grown on soil mixed with biosolid. • In the outdoors trial biosolid renders higher disease tolerance in sandy soil. • Fusarium disease is less aggressive on tomato plants grown on biosolid mix. • Tolerance to disease is higher in sandy soil+biosolid than in clay soil+biosolid.

Application of sewage sludge for cereal production in a Mediterranean environment (Lebanon)

Purpose Management of sewage sludge generated from wastewater treatment plants is a big challenge for its potential reusage in agriculture. Most of the Lebanese local sludge is discarded in the water or in landfills (most wastewater plants are partially functional). The objective of this research was to assess the effect of the application of different sewage sludge rates on the wheat production as an alternative of chemical fertilizer. Method Field trials were conducted, for one-year study, in IAAT village in the Bekaa valley-Lebanon. The considered treatments of 4, 8 and 16 kg.m-2 rates were compared to a control treatment. Physicochemical and microbiological analysis were performed on sludge and soil samples (pre cultivation and post-harvest). The harvested wheat was also analyzed for several parameters as mineral content. Results Results presented significant differences between control and treatments. pH values decreased with biosolids additions; organic matter rose in the amended soils, macronutrients levels increased. Heavy metals outcome increased significantly after amendment, microbiological analysis didn’t show any contamination by Salmonella, E.Coli, Staphylococcus Aureus and Helminth eggs. As for wheat plants' evaluation, fiber and protein contents presented an increase similar to nitrogen and phosphorus. Conclusion These results are a key component that identifies the role of biosolids as pH regulator and soil conditioner which improves the physicochemical properties of soil without any risk of microbiological contamination. These results are promising and they encourage the use of biosolids as agriculture amendment.

Impacts of the addition of biochar, biosolid and aluminum silicate on the leaching and bioavailability of 2,4-D + picloram in soil

The use of herbicides in high-yield crops is increasing, and their fate in the environment has become a primary environmental concern. The aim of this study was to evaluate the impacts of the use of biosolid, biochar, and aluminum silicate on the leaching dynamics of a mixture of 2,4-D + picloram herbicides, which is widely used in agricultural and non-agricultural areas. Three experiments were carried out, one for each residue, using the same methodological procedure. The tests were designed in randomized blocks with four replicates and split plots. Different proportions of the residues were incorporated in the pots at 0%, 10%, 20%, 30%, and 40% referring to the column volume, allocated in the subplots at different depths in the soil column (0–5, 5–10, 10–15, 15–20, 20–25, 25–30, 30–35, 35–40, and 40–45 cm). After the application of 2,4-D + picloram, 40 mm of rain was simulated in all columns. The plant bioindicator, Cucumis sativus , was sown in the profile. The increase in the biochar dose intensified 2,4-D + picloram leaching and grew C. sativus biomass in deeper layers of the soil profile. Regarding biosolids, an increased dose reduced the 2,4-D + picloram movement in soil and stimulated the growth of C. sativus . The addition of aluminum silicate to the soil did not influence the leaching of 2,4-D + picloram. However, it increased the biomass of C. sativus plants in the deeper layers of the soil profile. The addition of biosolids reduced the leaching of 2,4-D + picloram in the soil profile. However, the incorporation of biochar and aluminum silicate did not decrease the risk of contamination of the deeper layers of soil. • The addition of residues in soil versus the leaching 2,4-D + picloram was evaluated. • Bioassay carried out used on soil columns, with Cucumis sativus as the bioindicator. • Biosolid reduces herbicide leaching in the soil profile and environmental risk. • Biochar increases herbicide leaching and availability in deeper soil layers. • Aluminum silicate behaves as inert for the herbicide movement and availability.

High throughput screening of native species for tailings eco-restoration using novel computer visualization for plant phenotyping.

Historical hard-rock mine activities have resulted in nearly half a million mining-impacted sites scattered around the US. Compared to conventional remediation, (aided) phytostabilization is generally cost-effective and ecologically productive approach, particularly for large-scale sites. Native species act to maintain higher local biodiversity, providing a foundation for natural ecological succession. Due to heterogeneity of mine waste, revegetation strategies are inconsistent in approach, and to avoid failure scenarios, greenhouse screening studies can identify candidate plants and amendment strategies before scaling up. This greenhouse study aimed to concurrently screen a variety of native species for their potential to revegetate Cu/Pb/Zn mine tailings and develop a high throughput and non-destructive approach utilizing computer vision and image-based phenotyping technologies to quantify plant responses. A total number of 34 species were screened in this study, which included: 5 trees, 8 grasses, and 21 forbs and legumes. Most of the species tested were Missouri native and prairie species. Plants were non-destructively imaged, and 15 shape and color phenotypic attributes were extracted utilizing computer vision techniques of PlantCV. Compared to reference soil, all species tested were negatively impacted by the tailings' characteristics, with lowest tolerance generally observed in tree species. However, significant improvement in plant growth and tolerance generally observed with biosolids addition with biomass surpassing reference soil for most legumes. Accumulation of Cu, Pb, and Zn was below Domestic Animal Toxicity Limits in most species. Statistically robust differences in species responses were observed using phenotypic data, such as area, height, width, color, and 9 other morphological attributes. Correlations with destructive data indicated that area displayed the greatest positive correlation with biomass and color the greatest negative correlation with shoot metals. Computer visualization greatly increased the phenotypic data and offers a breakthrough in rapid, high throughput data collection to project site-specific phytostabilization strategies to efficiently restore mine-impacted sites.

Blended municipal compost and biosolids materials for mine reclamation: Long-term field studies to explore metal mobility, soil fertility and microbial communities

Application of stable soil amendments is often the key to successful phytostabilization and rehabilitation of mine tailings, and microbial guilds are primary drivers of many geochemical processes promoted by these amendments. Field studies were set up at a tailings management area near Sudbury, Ontario to examine performance of blends of lime stabilized municipal biosolids and compost at nine different rates over thick (1 m) municipal compost covers planted with agricultural crops. Based on biogeochemical variability of the substrates four and ten years after application of the initial compost cover, the experimental plots could be classified into three categories: “Low” rate (0–100 t ha−1 biosolids), “Medium” rate (200–800 t ha−1), and “High” rate (1600–3200 t ha−1) treatments. The addition of biosolids materials to the thick compost cover at rates higher than 100 t ha−1 significantly reduced C:N ratio of the substrates, available phosphorus, and some of the nutrient cations, while notably increasing inorganic carbon and the potential solubility of Ni and Cu. This suggests that increasing biosolids application rates may not equivalently ameliorate soil quality and geochemical stability. Correspondingly, microbial communities were altered by biosolids additions, further intensifying the negative impacts of biosolids on long-term efficiency of the initial compost cover. Abundance of cellulose, hemicellulose, and lignocellulose decomposers (as key drivers of mineralization and humification) was significantly reduced by “Medium” and “High” rate treatments. Most DNA sequences with high affinity to denitrifiers were detected in “High” rate treatments where geochemical conditions were optimal for higher microbial denitrification activities. These findings have implications for improving the long-term efficiency of reclamation and environmental management programs in mine tailings of northern temperate climates.

Soil Amendment with Biosolids and Inorganic Fertilizers: Effects on Biochemical Properties and Oxidative Stress in Basil (Ocimum basilicum L.)

We investigated changes in biochemical activity of a soil cultivated with Ocimum basilicum L. plants and in the oxidative stress of plants caused by the addition of biosolids and inorganic fertilizer. A greenhouse experiment was set up; it consisted of pots containing basil plants to which different treatments with biosolids and fertilizers were added. After 10 and 210 days of the incorporation of the treatments, both the biochemical properties and oxidative stress of the plants were evaluated. Mineralization of nitrogen (N) and respiratory activity increased with a higher dose of biosolid after 10 days of application. After 210 days, there were no changes in the mineralization of N and respiratory activity, catalase showed an increase, while microbial biomass carbon decreased. In relation to the oxidative stress, there was a decrease in the anthocyanin antioxidant capacity, and 2,2-diphenyl-1-picrylhydrazyl (DPPH), total flavonoids, and phenolic compounds were observed in soils treated with biosolids. The results indicated that the biochemical properties of the soil were favored in the presence of biosolids because they increased, especially after 10 days of application. The antioxidant capacity decreased in the presence of biosolids, which suggests that the amendment does not affect such capacity, and therefore oxidative stress could be reduced.

Biosolids inhibit uptake and translocation of 14C-carbamazepine by edible vegetables in soil.

Biosolids are regarded as a major source of pharmaceutically active compounds (PhACs) in soil and may lead to their accumulation in plants and potential human risks through dietary intake. Using 14C labeling, we explored the effect of biosolids on the uptake and tissue distribution of carbamazepine (CAB) by three ready-to-eat vegetables (i.e., carrot, celery, and pak choi) under greenhouse conditions. The 14C-CAB was consistently detected in vegetables and plant tissues with bioconcentration factors in a range of 1.28-37.69, and it was easily translocated from root to leaf and/or stem with translocation factors > 1. The inhibition on the uptake and accumulation of 14C-labeled carbamazepine from soil by the addition of biosolids was consistently observed, and such inhibitory effect was related to the biosolid amendment rates, the category of vegetable, and the plant growth stages. The influence of biosolids on behavior of CAB and other emerging pollutants in the soil-plant system should be considered in their environmental risk assessment.

The Impact of Biosolids on the Geotechnical Properties of Some Soils of the Niger Delta Sub-region, Nigeria

The production of biosolids (human wastes) in the Niger Delta of Nigeria has been taking place since man inhabited the sub-region. One of the negative impacts of <i>biosolids</i> is the changes to the geo-environmental conditions of the soils of the sub-region. Studies carried out on the effects of biosolids in the Niger Delta Sub-region over the last sixteen years indicate that the conventional geo-environmental engineering properties of the soils have been altered significantly. Biosolids have been found to affect both the grain size distribution patterns, the Atterberg Limits (Liquid Limits (LL), Plasticity indices (PI), California Bearing Rations (CBRs), Proctor Compaction indices such as Maximum Dry Densities (MDD); Optimum Moisture Contents (OMC), Soil friction angles () & cohesion values (c) and to an extent Ultimate Bearing Capacities (ϥ_ult. & ϥ_allow). Biosolids applied on two types of tropical soils classified as slightly to medium plastic (lateritic (CL) and Sandy (SP) soils) batched and mixed at four different percentage levels of 5%, 10%, 15% and 20% by weight of sample indicated that % biosolids in the soils positively correlated with the Total Organic Contents (TOC) while inversely correlating with the Moisture content in the lateritic soils to a limiting value at 15%, while in the basically sandy soil it was at the 20% biosolids treatment. The infiltration rate increased to a peak at 13.5% biosolids content and thereafter decreased, while in the basically sandy soil, addition of biosolids caused the infiltration rate to fluctuate. It has also been observed that 100kN is the critical stress under which high volume reduction is recorded in all cases of biosolids treatments. The 5 to 10% biosolids treatment range experienced minimum volume change (∆v) compared to the 15 to 20% biosolids treatment range. The wide gap observed existing between 15 – 20% and 0 – 10% biosolids treatment ranges tends to suggest the existence of two groups of biosolids-treated lateritic soils namely: the Low and High Compressible Lateritic soils.

Availability of lead in agricultural soils amended with compost of biosolid with wood shavings and yard trimmings.

Lead-polluted agricultural soils are a serious problem for food safety, with organic amendment being a promising mitigation method from the environmental perspective. Therefore, the purpose of this study was to evaluate lead availability and the effectiveness of the application of compost of biosolid with wood shavings and yard trimmings in contaminated soils. The physicochemical (Pb distribution, organic matter, pH, electric conductivity, cation exchange capacity, nitrogen, phosphorus, carbon, carbonates, exchangeable cations, sodium) and biological parameters (the microbial activity obtained by fluorescein diacetate hydrolysis) in Pb-polluted and non-polluted agricultural soils were evaluated after the addition of biosolid with wood shavings and yard trimming compost. Topsoils (lead-polluted and control) were collected in the vicinity of a former battery-recycling plant, amended with compost (0%, 5%, and 10%), and incubated in controlled conditions for 118 days. The results showed that lead availability decreased significantly, and the nutritional quality of the soils increased in the soils amended with 10% of compost. Taken together, the results of the present study indicated that compost amendment could be an effective method for mitigating the negative effects of lead in agricultural soils.