Rogelio Nogales

VERMICOMPOSTING OF SLUDGES FROM PAPER MILL AND DAIRY INDUSTRIES WITH EISENIA ANDREI: A PILOT-SCALE STUDY

Abstract We studied vermicomposting with Eisenia andrei of sludges from a paper mill mixed with cattle manure in a six-month pilot-scale experiment. Initially, a small-scale laboratory experiment was carried out to determine the growth and reproduction rates of earthworms in the different substrates tested. In the pilot-scale experiment, the number of earthworms increased between 22- and 36-fold and total biomass increased between 2·2- and 3·9-fold. The vermicomposts were rich in nitrogen and phosphorus and had good structure, low levels of heavy metals, low conductivity, high humic acid contents and good stability and maturity. These sludges could be potentially useful raw substrates in larger commercial vermicomposting systems, and would reduce the costs related with the exclusive use of different types of farm wastes as feed for earthworms.

Enzyme activities as indicators of the stabilization of sewage sludges composting with Eisenia foetida

Evolution of earthworm (Eisenia foetida, Savigny) biomass and changes in enzyme activities during 18 weeks of sewage sludge vermicomposting were studied. With time, hydrolase (β-glucosidase, urease, BAA-hydrolysing protease and phosphatase) and dehydrogenase (DH-ase) activities decreased as available organic compounds (water-soluble carbon) decreased. A high correlation among all enzyme activities and between each activity and the water-soluble carbon (WSC) led to the conclusion that both hydrolytic and dehydrogenase activities could be feasible indicators of the state and evolution of the organic matter. The ‘potential metabolic index’ (DH-ase/WSC) enabled distinguishing between hydrolytic and maturation phases in a sewage sludge vermicomposting process.

BIOCONVERSION OF SOLID PAPER-PULP MILL SLUDGE BY EARTHWORMS

Bioconversion of solid paper-pulp mill sludges and primary sewage sludge for 40 days at a ratio of 3:1 dw:dw was studied in containers with and without earthworms (Eisenia andrei). This mixture was a suitable medium for optimum growth and reproduction of the earthworms. Regardless of the presence of earthworms, degradation occurred during the bioconversion period, but the presence of earthworms accelerated the mineralization of organic matter, favored the breakdown of structural polysaccharides and increased the humification rate. Consequently, the C/N ratio and the degree of extractability of heavy metals were lower in the worm-worked end product.

Vermicomposting of Winery Wastes: A Laboratory Study

In Mediterranean countries, millions of tons of wastes from viticulture and winery industries are produced every year. This study describes the ability of the earthworm Eisenia andrei to compost different winery wastes (spent grape marc, vinasse biosolids, lees cakes, and vine shoots) into valuable agricultural products. The evolution of earthworm biomass and enzyme activities was tracked for 16 weeks of vermicomposting, on a laboratory scale. Increases in earthworm biomass for all winery wastes proved lower than in manure. Changes in hydrolytic enzymes and overall microbial activities during the vermicomposting process indicated the biodegradation of the winery wastes. Vermicomposting improved the agronomic value of the winery wastes by reducing the C:N ratio, conductivity and phytotoxicity, while increasing the humic materials, nutrient contents, and pH in all cases. Thus, winery wastes show potential as raw substrates in vermicomposting, although further research is needed to evaluate the feasibility of such wastes in large-scale vermicomposting systems.

Isolation by isoelectric focusing of humic-urease complexes from earthworm (Eisenia fetida)-processed sewage sludges

Abstract Vermicomposting is an eco-biotechnological process that transforms energy-rich and complex organic substances into a stabilized humus-like product. In a laboratory experiment, Eisenia fetida (Sav.) earthworms were employed to process putrescible sewage sludges into a high-value biofertilizer, very rich in urease activity and humic-urease complexes (stabilized extracellular enzymes). Extracellular humic-urease complexes were extracted by a single 24-h extraction at 37  °C using neutral pyrophosphate (0.1 M); then, the extracts were dialysed and characterized by means of an analytical isoelectric focusing technique. This technique gave a multiplicity of humic bands enzymatically active, with isoelectric points ranging from 4.8 to 5.6. The results demonstrated that, after an 18-week incubation period, sewage sludge had undergone a biochemical evolution, which caused a doubling of absolute urease activity and a six-fold increase in specific activity (activity with reference to the humic C fraction). The biochemical evolution of the vermicompost was evaluated also from the sharp decrease in pyrophosphate-extractable C and water-soluble C. Stabilization of organic C during vermicomposting and the activity of humic-urease complexes expressed at low pH values are of extreme importance when organic wastes are used in acid soils for biochemical restoration purposes.

Continuous-feeding vermicomposting as a recycling management method to revalue tomato-fruit wastes from greenhouse crops

Huge quantities of discarded fruits generated from greenhouse crops represent a worldwide environmental problem. The aim of this work was to assess the efficiency of vermicomposting as a recycling management option for biotransforming tomato-fruit wastes from greenhouses into an organic nutrient-rich product available for agricultural purposes. A pilot vermireactor was constructed. It was provided with a manure layer, where an initial population of Eisenia fetida was introduced and fed continuously at a high organic loading rate (13.6 kg TOC m(-3)wk(-1)) for 150 days. Vermicompost chemical and enzymatic parameters as well as the bacterial and fungal community structure were determined for 210 days (vermicomposting plus a maturation period). Earthworm biomass increased after 90 days, and then declined due to increasing pH, electrical conductivity and ammonium concentration. The temporal patterns of dehydrogenase, β-glucosidase, protease and urease were related to earthworm growth and the stabilization of organic matter. Bacterial DGGE profiles differed between the period of degradation of labile substrates and the maturation step. Fungal communities at the stage of maximum earthworm biomass differed most, suggesting a gut passage effect. The end product was chemically stable and enriched in nutrients, demonstrating that tomato-fruit wastes can be successfully vermicomposted into a valuable soil amendment. We suggest continuous-feeding vermicomposting as an environmentally sound management option for greenhouse wastes.

Dynamics of microbial communities related to biochemical parameters during vermicomposting and maturation of agroindustrial lignocellulose wastes.

Scarce information is available on the changes in abundance of microbial taxa during vermicomposting. Quantitative PCR and DGGE analysis were used to monitor variations in the microbial structure, relative abundance of four bacterial classes and fungi over the vermicomposting and maturation period of wet olive cake (O) and vine shoots (W). Multivariate correlation analysis between microbial structure and abundance, earthworm biomass and enzyme activities revealed similar and divergent interactions in both processes. Although Eisenia fetida development was different, significant correlations were found with β-glucosidase activity and with bacterial and fungal structure. In the vermicomposting period of O and W, a decline was found in bacteria (94% and 77%), fungi (93% and 94%), and Gammaproteobacteria (56% and 71%) but an increase in Betaproteobacteria and Actinobacteria (62-79%). Alphaproteobacteria increased only in O (26%). Despite the different initial lignocellulose wastes, the mature vermicomposts were similar in microbial and biochemical properties.

Evaluation of the sorption process for imidacloprid and diuron in eight agricultural soils from southern Europe using various kinetic models.

Kinetic studies are of great concern for understanding the processes and parameters involved in the sorption of pollutants by soils. Sorption kinetics of imidacloprid and diuron in eight soils of different characteristics, with very low organic carbon content were investigated. Pseudosecond-order kinetic reactions closely correlate with the experimental kinetic (R(2) > 0.98) in all soils. The sorbed amount of diuron was higher than that for imidacloprid. The low OC content of these soils correlated neither with the sorbed amount nor with the kinetic parameters for both pesticides. Imidacloprid sorption was correlated with silt and sand content and cation exchange capacity (CEC); meanwhile for diuron, no correlation was found. Thus, sorption kinetics take place throughout different mechanisms related mainly to the chemical character of the pesticides. Sorption kinetic parameters determined using three of the four models selected (pseudosecond-order kinetic reactions, Elovich equation, and Weber-Morris models) have been shown to be worthy to distinguish the process controlling the sorption kinetic of both pesticides.

Feasibility of vermicomposting for vegetable greenhouse waste recycling

This study was conducted in order to evaluate the feasibility of Eisenia andrei for vermicomposting heterogeneous-plant (HP), tomato-plant (P), and damaged tomato-fruit (T) greenhouse vegetable wastes. Earthworm growth and reproduction were monitored over a 12-week period, and variations in chemical parameters, enzyme activity, phytotoxicity test, and genetic fingerprinting of bacterial communities were evaluated. While high rates of salinity prevented earthworm survival in HP and P (>10 dS m(-1)), T was vermicomposted recording an adequate earthworm growth and cocoon production. The latter waste was successfully stabilized, as indicated by the significant decrease in its TOC content ( approximately 13-26%) and C:N ratio ( approximately 16-36%) and its high germination indices ( approximately 39-72%). The similar enzyme activities levels and bacterial community fingerprintings recorded in diverse vermicomposts obtained from T waste indicate that this type of waste favoured the existence of analogous bacterial communities responsible for the high degree of stabilization and maturity detected.

Biosolids and biosolids-ash as sources of heavy metals in a plant-soil system

Generally, the potential for biosolids (digested or composted)to contribute heavy metals to the soil-plant system has beencompared with commercial fertilizers and other organic wastesbut not with biosolids-ash. An column study was conducted in agreenhouse to determine the availability, extractability andleachability of metals in a degraded, non-calcareous soilamended with different biosolids (200 Mg ha-1). Thebiosolids investigated were dewatered, anaerobically digestedbiosolids, composted biosolids and biosolids-ash. The columns(26 cm) were planted with wheat (Triticum aestivum L. cvMexa). The addition of digested biosolids decreased the drymatter yield of wheat. Treatments including organic biosolidsincreased Cu and Zn concentrations in wheat roots, straw andgrain, whereas the addition of biosolids-ash did not affect theconcentrations of these metals in wheat. Concentrations of Ni,Co, Pb, Cr and Cd in wheat were below reliable detection limits(0.06, 0.05, 0.1, 0.06 and 0.02 mg kg-1, respectively).After harvesting, total and AB-DTPA extractable Cu, Zn and Pbincreased in the upper layer of the soil amended with thedifferent biosolids studied, whereas levels of AB-DTPAextractable Ni and Co were affected only when the soil wasamended with digested or composted biosolids. Total chromiumincreased only in treatments including organic biosolids. TheAB-DTPA extractable Cu, Zn and Pb in the lower layer of thesoil in treatments including biosolids evidenced downwardmovement of these metals. However, absence of these metals incolumn leachates indicates that this movement was gradual.