Effect of composted textile sludge on growth, nodulation and nitrogen fixation of soybean and cowpea

Methods for Natural and Synthetic Polymers Recovery from Textile Waste

Trends in the textile industry show a continuous increase in the production and sale of textile materials, which in turn generates a huge amount of discarded clothing every year. This has a negative impact on the environment, on one side, by consuming resources—some of them non-renewables (to produce synthetic polymers)—and on the other side, by polluting the environment through the emission of GHGs (greenhouse gases), the generation of microplastics, and the release of toxic chemicals in the environment (dyes, chemical reagents, etc.). When natural polymers (e.g., cellulose, protein fibers) are used for the manufacturing of clothes, the negative impact is transferred to soil pollution (e.g., by using pesticides, fertilizers). In addition, for the manufacture of clothes from natural fibers, large amounts of water are consumed for irrigation. According to the European Environment Agency (EEA), the consumption of clothing is expected to increase by 63%, from 62 million tonnes in 2019 to 102 million tonnes in 2030. The current article aims to review the latest technologies that are suitable for better disposal of large quantities of textile waste.

Dynamics of bacterial and archaeal communities along the composting of tannery sludge

The process of composting has been proposed as a biological alternative to improve the quality of tannery sludge (TS) by the action of microbial communities. However, there is limited knowledge about the dynamic of these microbial communities during the composting process. This study assessed the responses of bacterial and archaeal communities during TS composting using the 16S rRNA sequencing. The composting process occurred within 90 days, and samples of compost were collected on day 7 (d7; mesophilic stage), 30 (d30; thermophilic stage), 60 (d60; cooling stage), and 90 (d90; maturation stage). The results showed a succession of microbial phyla during the composting with enrichment of Synergistetes, WS1, and Euryarchaeota at the mesophilic stage, while at the thermophilic stage, there was an enrichment of Hydrogenedentes, WPS-2, Chloroflexi, and Deinococcus-Thermus. At the cooling stage, there was an enrichment of Kiritimatiellaeota, and at the maturation stage, there was an enrichment of Entotheonellaeota, Dadabacteria, Nitrospirae, Dependiatiae, and Fibrobacteres. When analyzing the drivers influencing microbial communities, Cr and pH presented more negative correlations with general phyla. In contrast, S, C, K, temperature, and N presented more positive correlations, while Ni, Cd, and P showed fewer correlations. According to niche occupancy, we observed a decreased proportion of generalists with a consequently increased proportion of specialists following the composting process. This study showed that different stages of the composting present a specific microbial community structure and dynamics, which are related to some specific composting characteristics.

Using textile industrial sludge, sewage wastewater, and sewage sludge as inoculum to degrade recalcitrant textile dyes in a co-composting process: an assessment of biodegradation efficiency and compost phytotoxicity

Recalcitrant dyes found in textile wastewater represent a threat for sustainable textile production due to their resistance to conventional treatments. This study assessed an alternative co-composting system for the treatment of recalcitrant textile dyes where textile industrial sludge, sewage wastewater, or sewage sludge were used as microbial compost inocula. The biodegradation efficiency of bioreactor trials and compost quality of the co-composting system were assessed by visible spectrophotometry and by a phytotoxicity test. The co-composting system (dry weight (dw) basis) consisted of 200 g of restaurant organic residues + 200 g sewage sludge (or 100 mL sewage wastewater, or 200 g textile sludge) + 100 mL of a 10% dye solution (Reactive Red 195, or Synolon Brown, or Orange Remazol, or Yellow Synozol, or Reactive Orange 122, or Reactive Black 5). After 60 days of composting, all dyes were biodegraded according to spectrophotometric data, with efficiency varying from 97.2 to 99.9%. Inoculum efficiency ranking was textile sludge > sewage sludge > sewage wastewater. Regarding compost quality, a phytotoxicity study with lettuce showed no toxicity effect. Thus, co-composting can be a low-cost and efficient method for recalcitrant textile dye biodegradation and for managing textile sludge in terms of waste recycling, contributing to environmental sustainability.

Improving the Fertigation of Soilless Urban Vertical Agriculture Through the Combination of Struvite and Rhizobia Inoculation in Phaseolus vulgaris

Soilless crop production is a viable way to promote vertical agriculture in urban areas, but it relies extensively on the use of mineral fertilizer. Thus, the benefits of fresher, local food and avoiding the transportation and packaging associated with food import could be counteracted by an increase in nutrient-rich wastewater, which could contribute to freshwater and marine eutrophication. The present study aimed to explore the use of mineral fertilizer substitutes in soilless agriculture. Phaseolus vulgaris (common bean) was fertilized with a combination of slow-releasing fertilizer struvite (a source of N, P, and Mg), which is a byproduct of wastewater treatment plants, and inoculation with Rhizobium (a N₂-fixing soil bacteria). The experiment included three bean-production lines: (A) 2 g/plant of struvite and rhizobial inoculation; (B) 5 g/plant of struvite and rhizobial inoculation, both irrigated with a Mg-, P-, and N-free nutrient solution; and (C) a control treatment that consisted of irrigation with a full nutrient solution and no inoculation. Plant growth, development, yields, and nutrient contents were determined at 35, 62, and 84 days after transplanting as well as biological N₂ fixation, which was determined using the ¹⁵N natural abundance method. Treatments A and B resulted in lower total yields per plant than the control C treatment (e.g., 59.35 ± 26.4 g plant^-1 for A, 74.2 ± 23.0 g plant^-1 for B, and 147.71 ± 45.3 g plant^-1 for C). For A and B, the nodulation and N₂ fixation capacities appeared to increase with the amount of initially available struvite, but, over time, deficient levels of Mg were reached as well as nearly deficient levels of P, which could explain the lower yields. Nevertheless, we conclude that the combination of struvite and N₂-fixing bacteria covered the N needs of plants throughout the growth cycle. However, further studies are needed to determine the optimal struvite quantities for vertical agriculture systems that can meet the P and Mg requirements throughout the lifetime of the plants.

A techno-sustainable bio-waste management strategy for closing chickpea yield gap

Sustainable development goals imply environmentally sound management of all wastes to minimize the waste generation through prevention, reduction, recycling, and reuse. In particular, the poultry industry produces nutrient-rich waste that requires proper management.Additionally, the recycling of bio-wastes in agricultural lands is still a key technology for the sustainable use of nutrients as a renewable fertilizer. Currently, there are very few studies on the utilization of agro-industrial bio-wastes, such as poultry abattoir sludge (PAS), for crop cultivation in soils containing low organic matter and high pH. In this context, it is necessary to make a more particular assessment of poultry industry-oriented and locally available nutrient-rich organic wastes for nodulation, physiological adaptation, and crop yield. Considering the scarcity of the literature in this field, the present study aimed to fulfill the apparent gap by focusing on the applicability of recycled PAS to low fertility soil in the growth of chickpea selected as a model legume, thereby contributing to the development of an agricultural and sustainable industrial management strategy for the relevant sectors. In this study, leaf chlorophyll content and nodule color were also investigated by the image analysis methodology to describe the effects of bio-waste on closing chickpea yield gap in a marginal land with high soil pH and low organic matter. Two-year consecutive field experiments were carried out to explore the effect of the PAS with the application rates of 25 kg N ha^-1 (T₂), 50 kg N ha^-1 (T₃), and 100 kg N ha^-1 (T₄) along with unamended (T₀) and fertilized control (T₁). The results indicated that the PAS treatments significantly differed in chlorophyll content, nodulation parameters, and biomass and grain yields. The chlorophyll content was correlated (r = 0.910) with the red color value (RGB color model) of nodule image analysis in the response to bio-waste. Based on the two-year average, it was concluded that chickpea yield could be increased 45% by amending with the PAS (T₃). The present study clearly demonstrated that the image analysis could be a useful digital tool for the evaluation of chlorophyll content, nitrogen fixation efficiency, and forecasting biomass and grain yields of chickpea. The results also confirmed that the PAS application to low fertility soil could prominently contribute to establish sustainable waste management and crop production alternatives for closing chickpea yield gap.

Uptake Prediction of Ten Heavy Metals by Eruca sativa Mill. Cultivated in Soils Amended with Sewage Sludge

This study was carried out to develop mathematical regression equations for predicting the uptake of ten heavy metals (HMs) (cadmium, Cd; cobalt, Co; chromium, Cr; copper, Cu; iron, Fe; manganese, Mn; molybdenum, Mo; nickel, Ni; lead, Pb; zinc, Zn) by a vegetable species (Eruca sativa Mill.) in the Abha region (Saudi Arabia) based on the concentration of these HMs in soils amended with sewage sludge, organic matter (OM) content and soil pH. The resultant regression equations indicated that the three soil factors were significant predictors for the uptake of the ten HMs in the plant tissues. By applying a t test, we found that there are no significant differences between the actual and predicted values of the ten HMs in the E. sativa roots and leaves (P > 0.05), which reflects the goodness of fit of these equations for predicting the uptake of these HMs. Such types of equations may be helpful for evaluating the risk of cultivation of E. sativa plants in soils amended with sewage sludge.

Enhanced nodulation and higher germination using sludge ash as a carrier for biofertilizer production

Sludge ash, a byproduct resulting from the combustion of the dewatered sludge generated in the sewage treatment plants, is recognized as a hazardous solid waste throughout the world. This solid waste, which is produced in behemoth volume, has very limited applications and is directly disposed to landfills. The present study aims to explore a novel strategy for utilizing this solid waste for the development of Rhizobium biofertilizer and thus reducing the burden on landfills. The Rhizobium inoculum was prepared and mixed with sludge ash to formulate Rhizobium biofertilizer, and shelf life of this formulation was evaluated by counting colony forming unit. The prepared formulation was applied on lentil seeds, and its effect was analyzed by assessing the plant growth along with other yield characteristics. Enhanced colony forming unit count (6487.78) was observed in sludge ash carrier combination with a better shelf life of five months in comparison to lignite carrier formulation from the beginning of the experiment (9.1%) till 150th day (69.8%). Lentil seeds treated with sludge ash based biofertilizer showed luxuriant growth with 19% enhanced root length, 42% in number of nodules, 10% in plant growth and 53.40% in seed yield as compared to conventional lignite formulations. Hence, biofertilizer produced from waste material sludge ash is not supposed to cause a hazard for the soil and plants when incorporated in defined amount and can prove to be a substitute for conventional lignite carrier in biofertilizer production.

Dynamics of archaeal community in soil with application of composted tannery sludge

Application of composted tannery sludge (CTS) could promote a shift in the structure of soil microbial communities. Although the effect of CTS on bacterial community has been studied, it is unclear how the composition and diversity of archaeal community respond to CTS amendment and which environmental factors drive the community over time. Here, we hypothesize that the Archaea structure and composition respond to CTS amendment over the time. CTS had been previously applied annually along 6 years and this assessment occurred for 180 days following the application in the 7^th year by using different rates (0, 2.5, 5, 10 and 20 ton ha⁻¹). We used amplicon 16S rRNA sequencing to assess the changes in the structure of the archaeal community. Thaumarchaeota and Euryarchaeota were the most abundant phyla found in soils with application of CTS, with Thaumarchaeota dominating the sequences in all samples with relative abundances of >98%. We observed a decreasing trend on the archaeal diversity over the time with increasing CTS application rate, together with an increase in the community similarity. The redundancy analyses (RDA) explained 43% of the total variation in operational taxonomic units and identified Na, pH, Cr and P as the main drivers of the archaeal community over time after application of highest CTS rates. CTS application changes the structure of Archaea community, with significant increase of Thaumarchaeota and Aenigmarchaeota groups, which can be further explored for its biotechnological use in contaminated soils.

Prediction models for evaluating the uptake of heavy metals by cucumbers (Cucumis sativus L.) grown in agricultural soils amended with sewage sludge

Heavy metal (HM) concentrations in edible plants can develop many serious health risks to humans. The precise prediction of plant uptake of HMs is highly important. Thus, the present investigation was carried out to develop regression models for predicting the concentrations of HMs in cucumbers (Cucumis sativus L.) from their concentration in the soil and using the organic matter (OM) content and soil pH as co-factors. The results showed that cucumber roots had the highest significant concentrations of all HMs at P < 0.001, except Cd, Cu, and Zn were in fruits. The lowest concentrations of Cd, Co, Cr, Mn, Ni, and Pb were recorded in stems. HM concentrations in cucumbers were strongly correlated with soil HM, pH, and OM content. Soil pH and OM content had negative and positive correlations with all HMs in cucumber tissues, respectively. Regression analysis indicated that soil HM, pH, and OM contents were good predictors for HM concentrations in cucumbers. The regression models for root Co, Cr, Fe, and Zn were described by high model efficiency values that explain 48-58% variability. The best regression models for cucumber stem were for Cu, Mn, Ni, and Zn that are characterized by high R² and model efficiency values. For cucumber fruits, R² values were ranged from 54 to 82%, with best models for Cr, Pb, Cd, Cu, Ni, and Co in the fruit. We expect that these models will be beneficial for risk assessment studies on sewage sludge utilization in agriculture.

The mechanism of enhanced wastewater nitrogen removal by photo-sequencing batch reactors based on comprehensive analysis of system dynamics within a cycle

To understand the mechanism of enhanced nitrogen removal by photo-sequencing batch reactors (photo-SBRs), which incorporated microalgal photosynthetic oxygenation into the aerobic phases of a conventional cycle, this study performed comprehensive analysis of one-cycle dynamics. Under a low aeration intensity (about 0.02 vvm), a photo-SBR, illuminated with light at 92.27 μ·mol·m^-2·s^-1, could remove 99.45% COD, 99.93% NH₄⁺-N, 90.39% TN, and 95.17% TP, while the control SBR could only remove 98.36% COD, 83.51% NH₄⁺-N, 78.96% TN, and 97.75% TP, for a synthetic domestic sewage. The specific oxygen production rate (SOPR) of microalgae in the photo-SBR could reach 6.63 fmol O₂·cell^-1·h^-1. One-cycle dynamics shows that the enhanced nitrogen removal by photo-SBRs is related to photosynthetic oxygenation, resulting in strengthened nitrification, instead of direct nutrient uptake by microalgae. A too high light or aeration intensity could deteriorate anoxic conditions and thus adversely affect the removal of TN and TP in photo-SBRs.

Fresh and composted industrial sludge restore soil functions in surface soil of degraded agricultural land

A field study was conducted to test the potential of 5-year consecutive application of fresh industrial sludge (FIS) and composted industrial sludge (CIS) to restore soil functions at surface (0-15cm) and subsurface (15-30cm) of the degraded agricultural land. Sludge amendments increased soil fertility parameters including total organic carbon (TOC), soil available nitrogen (SAN), soil available phosphorus (SAP) and soil available potassium (SAK) at 0-15cm depth. Soil enzyme activities i.e. dehydrogenase (DHA), β-glucosidase (BGA) and alkaline phosphatase (ALp) were significantly enhanced by FIS and CIS amendments in surface soil. However, urease activity (UA) and acid phosphatase (ACp) were significantly reduced compared to control soil. The results showed that sludge amendments significantly increased microbial biomass nitrogen (MBN) and microbial biomass phosphorus (MBP) at both soil depth, and soil microbial biomass carbon (MBC) only at 0-15cm depth. Significant changes were also observed in the population of soil culturable microflora (bacteria, fungi and actinomycetes) with CIS amendment in surface soil suggesting persistence of microbial activity owing to the addition of organic matter source. Sludge amendments significantly reduced soil heavy metal concentrations at 0-15cm depth, and the effect was more pronounced with CIS compared to unamended control soil. Sludge amendments generally had no significant impact on soil heavy metal concentrations in subsoil. Agronomic viability test involving maize was performed to evaluate phytotoxicity of soil solution extract at surface and sub-surface soil. Maize seeds grown in solution extract (0-15cm) from sludge treated soil showed a significant increase of relative seed germination (RSG), relative root growth (RRG) and germination index (GI). These results suggested that both sludge amendments significantly improved soil properties, however, the CIS amendment was relatively more effective in restoring soil functions and effectively immobilizing wastewater derived heavy metals compared to FIS treatment.

Soil microbial properties after 5 years of consecutive amendment with composted tannery sludge

Composting has been recognised an alternative method to tannery sludge recycling and afterwards to be used in agriculture. As the tannery sludge contains salts and chromium, the application of composted tannery sludge (CTS) should be performed carefully to minimise negative effects on soil microbial properties. Therefore, this study evaluated the effects of 5-year repeated CTS amendment on soil microbial biomass (SMB) and enzyme activities in a tropical soil. CTS was applied during 5 years at 0, 2.5, 5, 10 and 20 Mg ha(-1), and at the fifth year, the microbial biomass C (MBC) and N (MBN), basal and substrate-induced respiration (SIR), metabolic quotient (qCO₂) and dehydrogenase (DHA) and fluorescein diacetate (FDA) hydrolysis were determined in the soil samples. Soil MBC and MBN showed the highest values with the amendment of 5 Mg ha(-1) CTS. Soil respiration increased with the increase in CTS rates, while SIR showed the highest values with the amendment of 0, 2.5 and 5 Mg ha(-1) CTS. DHA activity showed the highest values with the amendment up to 2.5 Mg ha(-1), while FDA hydrolysis increased up to the rate of 5 Mg ha(-1) CTS. The results show that after 5 years of permanent amendment of CTS, soils amended with 2.5 Mg ha(-1) have SMB and enzymatic activities similar to those in unamended soil.

The impact of sewage sludge compost on tree peony growth and soil microbiological, and biochemical properties

In order to assess the suitability of sludge compost application for tree peony (Paeonia suffruticosa)-soil ecosystems, we determined soil microbial biomass C (Cmic), basal respiration (Rmic), enzyme activities, and tree peony growth parameters at 0-75% sludge compost amendment dosage. Soil Cmic, Rmic, Cmic as a percent of soil organic C, enzyme (invertase, urease, proteinase, phosphatase, polyphenoloxidase) activities, and plant height, flower diameter, and flower numbers per plant of tree peony significantly increased after sludge compost amendment; however, with the increasing sludge compost amendment dosage, a decreasing trend above 45% sludge compost amendment became apparent although soil organic C, total Kjeldahl N, and total P always increased with the sludge compost amendment. Soil metabolic quotient first showed a decreasing trend with the increasing sludge compost application in the range of 15-45%, and then an increasing trend from compost application of 45-75%, with the minimum found at compost application of 45%. As for the diseased plants, 50% of tree peony under the treatment without sludge compost amendment suffered from yellow leaf disease of tree peony, while no any disease was observed under the treatments with sludge compost application of 30-75%, which showed sludge compost application had significant suppressive effect on the yellow leaf disease of tree peony. This result convincingly demonstrated that ≤45% sludge compost application dosage can take advantage of beneficial effect on tree peony growth and tree peony-soil ecosystems.

Relationship between photosynthetic capacity, nitrogen assimilation and nodule metabolism in alfalfa (Medicago sativa) grown with sewage sludge

Sewage sludge has been used as N fertilizer because it contains some of inorganic N, principally as nitrate and ammonium ions. However, sewage sludge addition to legumes could result in impaired nodule metabolism due to the presence of inorganic N from sludge. A greenhouse experiment was conducted to examine the effects of sewage sludge on growth, photosynthesis, nitrogen assimilation and nodule metabolism in alfalfa (Medicago sativa L. cv. Aragón). Plants were grown in pots with a mixture of perlite and vermiculite (2:1, v/v). The experiment included three treatments: (1) plants inoculated with rhizobia and amended with sewage sludge at rate of 10% (w/w) (RS); (2) plants inoculated with rhizobia without any amendment (R); and (3) non-inoculated plants fed with ammonium nitrate (N). N(2)-fixing plants had lower growth and sucrose phosphate synthase activity but higher photosynthesis than nitrate-fed plants because they compensated the carbon cost of the rhizobia. However, sewage sludge-treated plants evidenced a loss of carbon sink strength due to N(2) fixation by means of decreased photosynthetic capacity, leaf chlorophylls and N concentration in comparison to untreated plants. Sewage sludge did no affect nodulation but decreased nodule enzyme activities involved in carbon and N metabolisms that may lead to accumulation of toxic N-compounds.

Effect of different tannery sludge compost amendment rates on growth, biomass accumulation and yield responses of Capsicum plants

Composting has been recognized as one of the most cost effective and environmentally sound alternatives for organic wastes recycling from long and composted wastes have a potential to substitute inorganic fertilizers. We investigated the potential of composted tannery sludge for ornamental purposes and to examine the effects of two different composts and concentrations on ornamental Capsicum growth. The two composts were produced with tannery sludge and the composition of each compost was: compost(1) of tannery sludge (C(1)TS) - tannery sludge+sugarcane straw and cattle manure mixed in the ratio 1:3:1 (v:v:v); compost(2) of tannery sludge (C(2)TS) - tannery sludge+"carnauba" straw and cattle manure in the ratio 1:3:1 (v:v:v). Each compost was amended with soil at rates (% v:v) of 0%, 25%, 50%, 75% and 100% (designation hereafter as T(1)-T(5), respectively). The number of leaves and fruits were counted, and the stem length was also measured. Chlorophyll content was recorded on three leaves of each harvested plant prior to harvest. Number of leaves and fruits, stem length, dry weight of shoot and roots did not vary significantly between the plants grown in two tannery composts. All the treatments with composted tannery sludge application (T(2)-T(5)) significantly increased the number of leaves and fruits, stem length and chlorophyll content compared with the control (T(1)). The chlorophyll content was higher in plants growing in the C(1)TS compared to C(2)TS. The results of the present study further suggest that Capsicum may be a good option to be grown on composted tannery amended soil.

Sewage sludge application can induce changes in antioxidant status of nodulated alfalfa plants

A greenhouse experiment was conducted to investigate the oxidative stress produced by sewage sludge addition on nodulated alfalfa (Medicago sativa L. cv. Aragón) plants. Two types of sludge were incorporated into substrate: anaerobic mesophilic digested (AM) and autothermal thermophilic aerobic digested (ATAD) sludge. Pots without sludge but with inoculated plants were used as control treatment for comparison. Results showed that sludge amended plants had increased tissue accumulation of heavy metals that induced oxidative stress. This is characterized by induction of the antioxidant enzymatic activities and alterations in the redox state of ascorbate. ATAD sludge application produced a reduction in nodulation, increased nodule antioxidant enzyme activities and decreased ascorbate/dehydroascorbate ratio. As a consequence, nodules of ATAD treatment suffered from oxidative damages as evidenced by high malondialdehyde levels. By contrast, AM application enhanced plant growth and no deleterious effects on nodulation were found. Nodules developed in AM sludge had increased antioxidant enzyme activities, ascorbate/dehydroascorbate ratio and improved capacity for thiol synthesis. Results clearly showed that nodulated alfalfa performed better in AM than in ATAD sludge and suggest that differential response appears to be mediated by plant ability to thiol synthesis and to maintenance of a more equilibrated antioxidant status.

De-inking sludge and phosphorus effects on growth and symbiotic dinitrogen fixation in forage legumes

The de-inking process produces a waste by-product, called de-inking paper sludge (DS), that contains paper fibers, clay particles and inks and high carbon (C) concentrations combined with low nitrogen (N) and phosphorus (P) concentrations. The use of high rates of DS to increase the soil organic matter thus requires provision of high rates of N and P for adequate plant growth. Using dinitrogen (N2)-fixing forage legumes is an alternative to N fertilization under such circumstances. In a greenhouse study, DS rates of 0, 50 or 100 Mg ha(-1) and five rates of P (40, 80, 120, 160, or 200 kg P2O5 ha(-1)) were applied on two soil types, a clay loam (Pintendre) and a silty clay loam (St-Augustin). Nitrogen uptake and symbiotic N2 fixation (SNF) were estimated in alfalfa (Medicago sativa L.), sweetclover (Melilotus officinalis L.) and red clover (Trifolium pratense L.); Bromegrass (Bromus inermis L.) and alfalfa ineffective for N2 fixation were used as the reference (non-N2 fixing) crops. Atmospheric N2 fixation was estimated by natural abundance of 15N (815N). Under controlled conditions, high rates of DS substantially reduced delta15N values, particularly with high rates of P. In addition, N uptake of legumes generally increased with increased P concentrations and it peaked with 120 or 160 kg P2O5 ha(-1). Correlated with the trends observed with delta15N values and it peaked with 120 or 160 kg P2O5 ha(-1). Present results showed that under high rates of application of DS and adequate P supply, forage legumes fixed more atmospheric N2. delta15N can be a good indicator of SNF under the above-mentioned conditions.