Enhanced vermicomposting of rice straw and pressmud with biogas slurry employing Eisenia fetida: Production, characterization, growth, and toxicological risk assessment

The biogas plant plays a dual role: it directly provides energy and indirectly promotes organic farming through outlet slurry. However, agricultural biomass wastes such as rice straws (RS) and pressmud (PM), which can't be used as fertilizers on their own, were vermicomposted (60 days) with biogas slurry (BS), using earthworm, into four blends: T1(BS, 100%), T2(3:2, BS: RS), T3(3:2, BS: PM), and T4(3:1:1, BS: RS: PM). The characterization, elemental analysis, and toxicological risk assessment of derived vermimanure were carried out using various analytical tools, such as an organic elemental analyzer such as CHNS, FT-IR, FESEM-EDXA, XPS, and ICP-OES. The pH, electrical conductivity, and C/N values were within 7.1-7.8, 3.2-6.0 dSm-1, and 12-15, respectively, for all treatments. The proportions of N (38%), P (70%), K (58%), Mg (67%), Ca (42%), and ash (44%), increased significantly (P < 0.05) over the initial feedstocks. The ecological risks of heavy metals (Zn, Cu, Ni, Pb, Cd, and Cr) in all feedstocks were found to be under WHO-permitted levels. The growth performance of earthworms was also considerably higher (P < 0.05) over the control feedstock group. The analytical methods verified that feedstock T4 (3:1:1, BS: RS: PM) was more porous, containing NH4+, PO43-, K+, and other nutrients. Pellets of all vermimanure groups keep 65-75% of the original volume. As well, when these pellets have been employed for agronomy and dispersed in the field, they will cause less dust than traditional or powdered compost or manure. In comparison to the control group, the synergistic approach of RS, PM, and BS in vermimanure significantly (P < 0.05) enhanced seed germination (83%), vigour index (42.5%), and decreased mean germination time by 27%. Furthermore, pot trials with Abelmoschus esculentus seed indicated that seedlings cultivated with 40% vermimanure of T4 (3:1:1, BS: RS: PM) mixed soil showed high growth in shoot, root, and plant yield.

Pressmud Subdue Phytoremediation Indices in Lead-Contaminated Soils: A Human Health Perspective

Direct discharge of waste into water bodies and mining are two major sources of lead contamination in ecosystems. Water scarcity promoted the usage of industrial effluent-contaminated waters for crop production, mainly in peri-urban areas. These wastewaters may contain heavy metals and pollute crop ecosystems. These metals can reach the living cell via contaminated raw foodstuffs that grow under these conditions and cause various ill effects in metabolic activities. In this study, graded levels of pressmud (0, 2.5, 5, 10 g/kg) were applied on lead imposed soil with different contamination levels (0, 100, 150, 300 mg/kg) and metal dynamics was studied in spinach crop. Experimental results showed that the addition of pressmud upto 10 mg/kg had decreased different phytoremediation indices in spinach crop. Whereas, increasing Pb level enhanced the indices' values, indicating accumulation of significant amount of Pb in spinach biomass. However, application of pressmud (upto 10 mg/kg) reduced the bioconcentration factor (BCF) from 0.182 to 0.136, transfer factor (TF) from 0.221 to 0.191, translocation efficiency 66.11-59.34%; whereas, Pb removal enhanced from 0.063 to 0.072 over control treatment. These findings suggest that application of pressmud declined Pb concentration, the BCF and the TF in test crop which lead to less chances of adverse effect in human. These information are very useful for effectively managing wastewater irrigated agricultural crop production systems.

Assessment of in situ stabilization and heavy metal toxicity reduction of sugar mill pressmud through pilot scale composting

Owing to a huge amount of industrial organic waste generation in the recent past, concerned industries are facing immense challenges for in situ treatment and disposal of such wastes. Therefore, in this study, the efficacy assessment of in situ windrow composting of pressmud (PM) produced by sugar industry has been investigated. Samples were grabbed and mixed from windrows having composting days of 15 (PM15), 30 (PM30), and 45 (PM45) and were collected along with a compost sample from the 60th day (PMC) windrow. An investigation of physico-chemical parameters including pH, electrical conductivity, moisture content, volatile solids (VS), ash content, biochemical oxygen demand, chemical oxygen demand, total nitrogen, and C/N ratio was performed for raw PM and other aforementioned samples. Moreover, speciation of heavy metals (Cu, Cr, Ni, Pb, Cd, and Zn), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopic analyses were performed for PM and PMC to evaluate the heavy metal toxicity and mineralogical and chemical changes. The analysis showed 20.33% reduction in VS content and 53.65% increase in TN content after 60 days of in situ windrow composting. The pH and EC values of PMC were found to be lesser than that of upper values recommended for agricultural purposes. Furthermore, the speciation analysis showed significant reduction in bioavailability of heavy metals. The XRD and FTIR results were confirmatory for transformation of heavy metals into relatively stable forms. The study recommends the windrow composting practice as effective bioconversion technique that stabilizes organic content, enhances humification, and diminishes heavy metal bioavailability for PM and similar other sludges.

Can Application of Pressmud Mediated Plant Nutrient Dynamics Under Lead Contaminated Soils of Indian Vertisol?

Long- term application of marginal quality water accumulated significant amount of pollutant into the soil. It reduces soil health parameters, and crop yield and their quality. In this regards, graded application of pressmud (PM), i.e. 0, 2.5, 5 and 10 g/kg was applied on lead (Pb) contamination level (0, 100, 150, 300 mg/kg) and evaluated interaction effect on plant nutrients uptake by spinach. Analytical data showed that increasing the PM levels enhanced the macro (phosphorus, potassium, sulphur) and micro-nutrient (zinc, copper, manganese, iron) concentration into the soil. Whereas, increasing the level of Pb significantly (p ≤ 0.05) reduced the P, K and S nutrient concentration and uptake pattern by spinach crop. Increasing PM levels (control to 10 g/kg soil) improved P, K and S by 46.99, 98.96 and 76.79%, respectively in soil. This study is useful to formulate management strategies for minimizing Pb contamination in the food chain by the application of PM mostly in peri-urban areas.

Dry tomb - bioreactor landfilling approach for enhanced biodegradation and biomethane generation from municipal solid waste Co-disposed with sugar mill pressmud

In this study, anaerobic co-landfilling of municipal solid waste (MSW) and sugar mill pressmud (PM) was performed in four different proportions [PM:MSW] viz. 0:1 (control: BR1), 1:3 (BR2), 1:1 (BR3) and 3:1 (BR4). Efficacy assessment of Dry tomb - Bioreactor landfill (DTLF - BRLF) operation was carried out through leachate characterization and biomethane production. Leachate recirculation as a part of bioreactor operation after 194th day onwards showed promising degradation of co-wastes. Moreover, leachate decontamination and methane production were reliant on co-disposal proportions of PM and MSW. Maximum biomethane generation of 46.355L was obtained in landfill lysimeter BR3 followed by BR4 (34.680L), BR2 (24.275L) and BR1 (12.850L). Both logistic function and Gompertz growth models showed efficient fitting (R² > 0.99) for observed methane production. This research could be a baseline study for selective operation of combined dry tomb and bioreactor landfilling at full scale in co-disposal scenarios.

Toxic effects of Red-S3B dye on soil microbial activities, wheat yield, and their alleviation by pressmud application

This study examined the effect of Red-S3B textile dye on soil microbial activities, uptake of the dye by wheat plants and growth on the dye-contaminated soil. Moreover, pressmud (PM) application was investigated for its alleviative effect on wheat yield and dye uptake by plants. Preliminarily, soil was spiked with a wide concentration range (0, 100, 250, 500, 750 and 1000 mg kg^-1 soil) of Red-S3B dye and wheat was grown for 42-days. The dye did not suppress the activities of soil enzymes and growth of wheat seedlings at 100 mg kg^-1; however, beyond this level the dye had a linear negative effect on these attributes. With 1000 mg dye kg^-1 soil, wheat seedling biomass, viable microbial count, soil respiration, dehydrogenase, phosphatase, and urease activities decreased by 84%, 33%, 45%, 69%, 24%, and 11%, respectively as compared to uncontaminated soil. Moreover, phosphorus and potassium content in wheat shoot decreased, while the nitrogen content increased in Red-S3B contaminated soil. In the subsequent pot experiment, PM application (12.5 g kg^-1 soil) was assessed to alleviate the adverse effect of moderately toxic level of Red-S3B dye (500 mg kg^-1 soil) on wheat growth and yield. Root and straw biomass, and grain yield of wheat decreased by 13, 19 and 12%, respectively in Red-S3B contaminated soil as compared to uncontaminated soil. However, PM application to dye-contaminated soil retrieved the dye-induced reduction in root and straw biomass and grain yield to become statistically (p ≤ 0.05) at par with control plants. The color of Red-S3B was clearly visible in spikes depicting that plants absorbed Red-S3B but probably could not metabolize it. Amending the dye-contaminated soil with PM decreased Red-S3B content in awns from 78 to 37 mg kg^-1. Hence, it is concluded that Red-S3B textile dye is highly toxic to soil microbes and wheat plants at levels exceeding 100 mg kg^-1 soil. Soil application of PM alleviates the adverse effect of Red-S3B dye on wheat growth through reducing its uptake by plants.

Enriched pressmud vermicompost production with green manure plants using Eudrilus eugeniae

Vermicomposting of pressmud with cow dung and nitrogenous green manures (Gliricidia sepium and Leucaena leucocephala) was carried out using Eudrilus eugeniae (50 days). The reduction in pH, total organic carbon, C/N ratio, water-soluble organic carbon (C_ws)/N_org and C/P ratios, and a pronounced increase in NPK contents and microbial population in vermicompost were observed. An enhanced TKN of 3.80% and 3.45% was recorded in vermicomposts of pressmud + cow dung + L. leucocephala (2:1:1) and pressmud + cow dung + G. sepium (2:1:1) respectively. The C/N and C_ws/N_org ratios in vermicompost ranged from 11.86 to 16.66 and 0.53 to 1.33, respectively. The activity of dehydrogenase, urease, acid and alkaline phosphatase declined towards the end, indicating the progression of vermicompost maturity. The pressmud and green manure substrates promoted more biomass of E. eugeniae, while cow dung with green manure combination favored reproduction. The amendment of cow dung and green manure plants to pressmud (2:1:1 ratio) results in nutrient-enriched vermicompost production.

Ozone pre-treatment of molasses-based biomethanated distillery wastewater for enhanced bio-composting

Composting is a biological process in which the organic matter is degraded by the mixed population of microorganisms in a moist aerobic environment to more stable and humidified end products. The composting process involves an interaction between the organic waste, microorganisms, moisture and oxygen. The molasses-based biomethanated distillery wastewater is presently effectively utilized with sugarcane pressmud through the composting process. The aim of present work was to evaluate the effect of ozone pretreatment on the rate of composting process and the quality of compost obtained. The GC-MS & FTIR analysis of ozone pretreated wastewater indicated the degradation and/or transformation of the organic compounds to simpler compounds present in the wastewater. Composting was performed by mixing fixed weight ratios of pressmud and different ratios of ozone pretreated wastewater (1:3, 1:4 and 1:5). The composting process was found to occur faster in the ozone pretreated wastewater for all the ratios as compared to the untreated wastewater. The final compost characteristics were found to be optimum for the 1:3 and 1:4 ratios of pressmud and wastewater. The bio-oxidative phase duration of composting has been reduced for the ozone pretreated wastewater.

Stimulation of extracellular invertase production from spent yeast when sugarcane pressmud used as substrate through solid state fermentation

Efforts were made to utilize the waste/by-product of two agro-process industries namely pressmud from sugar processing industries and spent yeast from distilleries manufacturing ethanol from cane molasses, for the production of microbial invertase. Our experimentation indicated that these two sources could be ideally utilized for the production of invertase through solid substrate fermentation (SSF). SSF with spent yeast had given highest specific activity of 430 U/mg in 72 h of fermentation. Inoculum percentage of yeast cells on pressmud was optimized as 50% (w/w) with a combination inoculum of spent yeast and fresh cultured yeast at a ratio of 7:3. Crude enzyme was characterized for optimum pH and temperature and maximum activity was recorded at pH 5.0 and at a temperature of 40°C. Impacts of metal ions and detergents on invertase action were studied in which Mn²⁺, Fe³⁺, Al³⁺ and detergents had enhanced the activity of the enzyme whereas Cu²⁺ and Zn²⁺ inhibited the enzyme activity. Purification of 9.8 folds was obtained by using three phase partition method.