Persistent polycyclic aromatic hydrocarbons removal from sewage sludge-amended soil through phytoremediation combined with solid-state ligninolytic fungal cultures.

Polycyclic aromatic hydrocarbons (PAHs) are widely present in the environment, causing increasing concern because of their impact on soil health, food safety and potential health risks. Four bioremediation strategies were examined to assess the dissipation of PAHs in agricultural soil amended with sewage sludge over a period of 120 days: soil-sludge natural attenuation (SS); phytoremediation using maize (Zea mays L.) (PSS); mycoremediation (MR) separately using three white-rot fungi (Pleurotus ostreatus, Phanerochaete chrysosporium and Irpex lacteus); and plant-assisted mycoremediation (PMR) using a combination of maize and fungi. In the time frame of the experiment, mycoremediation using P. chrysosporium (MR-PH) exhibited a significantly higher (P < 0.05) degradation of total PAHs compared to the SS and PSS treatments, achieving a degradation rate of 52 %. Both the SS and PSS treatments demonstrated a lower degradation rate of total PAHs, with removal rates of 18 % and 32 %, respectively. The PMR treatments showed the highest removal rates of total PAHs at the end of the study, with degradation rates of 48-60 %. In the shoots of maize, only low- and medium-molecular-weight PAHs were found in both the PSS and PMR treatments. The calculated translocation and bioconversion factors always showed values < 1. The analysed enzymatic activities were higher in the PMR treatments compared to other treatments, which can be positively related to the higher degradation of PAHs in the soil.

Bioremediation of the synthetic musk compounds Galaxolide and Tonalide by white rot fungal strain-assisted phytoremediation in biosolid-amended soil.

The study was aimed to conduct the bioremediation of synthetic musks by four species of white rot fungi combined with phytoremediation (Zea mays) in biosolid-amended soils where only Galaxolide (HHCB) and Tonalide (AHTN) were found as other musks were below the detection limit (0.5-2 µg/kg dw). The HHCB and AHTN concentration in natural attenuation treated soil was decreased by not more than 9%. In solely mycoremediation, Pleurotus ostreatus was found to be the most efficient fungal strain, with the higher (P < 0.05) HHCB and AHTN removal (51.3% and 46.4%). Phytoremediation-only of biosolid-amended soil was also able to remove HHCB and AHTN from soil significantly (P < 0.05) in comparison to the control treatment without plants which resulted in the final concentration for both compounds of 56.2 and 15.3 µg/kg dw, respectively. Using white rot fungus-assisted phytoremediation, only P. ostreatus decreased the HHCB content in soil significantly (P < 0.05) by 44.7%, when compared to the initial concentration. While using Phanerochaete chrysosporium, the AHTN concentration was decreased by 34.5%, which was a significantly lower concentration at the end of experiment compared to the initial value. Via fungus-assisted phytoremediation, the enzymatic activity and fungal biomass were increased, probably due to the presence of roots in association with the soil microbiome, in the process increasing the degradation of fragrances accordingly. This could lead to a higher (P < 0.05) AHTN removal in P. chrysosporium assisted phytoremediation. Estimated HHCB and AHTN bioaccumulation factors in maize were lower than 1, therefore no environmental risk would be posed.

Problems associated with vermicomposting of dog excrement in practice using Eisenia andrei.

One 25-kg dog produces about 500 g of excrement per day. Excrement is a potentially hazardous material, as it may contain pathogenic microorganisms. Our samples were tested for the presence of thermotolerant coliform bacteria, Enterococcus spp., Escherichia coli and Salmonella spp., which are indicators of faecal contamination, as well as for the presence of helminths and their eggs. During the experiment, it was observed whether these microorganisms could be eliminated by vermicomposting. There were two variants of vermicomposting piles: one test pile (with continuous feeding) and one control pile (with a single feeding). The vermicomposting process was run in outdoor conditions in park for 51 weeks using Eisenia andrei earthworms. The vermicomposting of dog excrement with waste from park maintenance (1:2) can produce a good quality fertiliser. During the process of vermicomposting, there was a gradual decrease in the content of pathogenic bacteria. At the end of the vermicomposting process, there were no eggs or adult helminths. The vermicompost was very rich in microorganisms and enzymatic activity. The pH value was slightly alkaline, and the C:N ratio corresponded to value of mature vermicompost.

Conversion of spent coffee grounds into vermicompost.

The present study was focused on vermicomposting of spent coffee grounds (SCG) and its mixtures with straw pellets. The process was evaluated in terms of biological and physico-chemical properties. The greatest number and biomass of earthworms was found in the treatment with 25% vol. SCG + 75% vol. straw pellets. In this treatment, the upper youngest layer exhibited 1.6-fold and 4.5-fold greater earthworm number and biomass, respectively, than the bottom oldest layer. Earthworm weight decreased in direct proportion to the layer age. The oldest treatment layer was characterized by lesser contents of fungi and six hydrolytic enzymes, compared to the younger layers. Further, the oldest treatment layer had suitable agrochemical properties. Earthworms were able to substantially reduce the caffeine stimulant content, which is considered the most representative pharmaceutically active compound.

Differences of Enzymatic Activity During Composting and Vermicomposting of Sewage Sludge Mixed With Straw Pellets.

The study aims were focused on profiling eight hydrolytic enzymes by fluorescence method using a multifunctional modular reader and studying the proportion of basic microorganism groups during composting and vermicomposting of sewage sludge mixed with straw pellets in several proportions (0, 25, 50, 75, and 100%). The greatest decrease in enzymatic activity occurred in the first half of composting and vermicomposting. After 4 months of these processes, the least enzymatic activity was observed in the sludge with 50% and also 25% straw addition, indicating that straw is an important means for the rapid production of mature compost from sewage sludge. Enzymatic activity was usually less in the presence of earthworms than in the control treatment because some processes took place in the digestive tract of the earthworm. For the same reason, we observed reduced enzyme activity during fresh feedstock vermicomposting than precomposted material. The final vermicompost from fresh feedstocks exhibited less microbial biomass, and few fungi and G- bacteria compared to precomposted feedstock. The enzymatic activity during composting and vermicomposting of sewage sludge and their mixtures stabilized at the following values: ß-D-glucosidase-50 µmol MUFG/h/g dw, acid phosphatase-200 µmol MUFP/h/g dw, arylsulphatase-10 µmol MUFS/h/g dw, lipase-1,000 µmol MUFY/h/g dw, chitinase-50 µmol MUFN/h/g dw, cellobiohydrolase-20 µmol MUFC/h/g dw, alanine aminopeptidase-50 µmol AMCA/h/g dw, and leucine aminopeptidase-50 µmol AMCL/h/g dw. At these and lesser values, these final products can be considered mature and stable.

Vermicomposting of sludge from a malt house.

Malting sludge is waste that could be used as a good soil conditioner after proper treatment. In the current study, the feasibility of vermicomposting malting sludge and its mixtures with straw pellets on the basis of physico-chemical and biological properties was verified. A vermicomposting system with continuous feeding of earthworms Eisenia andrei was used. The greatest number and biomass of earthworms was found in the variant with 25% malt house sludge + 75% straw pellets (on average of all layers: 320 earthworms/kg and 35 g/kg, respectively), followed by a variant with 50% malt house sludge + 50% straw pellets (on average of all layers: 47 earthworms/kg and 13 g/kg, respectively), indicating that a minimum of 50% (vol.) straw pellets is necessary for successful vermicomposting of malting sludge. Most earthworms lived in the youngest upper layer (42% and 52% of total number and earthworm biomass, respectively). On the contrary, the oldest bottom layers (final vermicomposts) after 180 days of vermicomposting were characterized by maturity, indicating lesser contents of microorganisms and enzyme activity. These vermicomposts had favorable agrochemical properties (pH = 7.8, EC = 1.2 mS cm-1, C/N = 11, Ptot = 1.23%, Ktot = 2.55%, Mgtot = 0.42%). The proportion of the available contents in the total contents were 10%, 59%, and 19% for P, K, and Mg, respectively.

Characterization of humic acids in a continuous-feeding vermicomposting system with horse manure.

The increasing numbers of kept horses create problems with processing horse manure as important local waste. This work was focused on horse manure vermicomposting in a real-field continuous-feeding system under controlled conditions, and on the complex study of the maturity and stability of the produced vermicompost. Commonly used simple indicators such as the C/N ratio, N-NH4+/N-NO3- ratio, DOC or ion exchange capacity, and also more advanced spectroscopic and thermoanalytic techniques were used and applied on the humic substances isolated from the vermicompost during its maturation (12 months in total). When compared with the original horse manure, vermicomposting decreased the aliphatic, protein-like, and polysaccharide humic components, whereas vermicomposting increased the aromaticity and contents of oxygen-containing functional groups. The typical tryptophan-like fluorophores in the manure, corresponding to the freshly produced organic matter of biological or microbial origin, were progressively transformed to humic-like fluorophores during vermicomposting. The most thermally labile humic fraction disappeared quickly during the very early vermicomposting stages. The results of spectroscopic and thermogravimetric analyses suggest that stable and mature vermicompost was produced after 6-9 months of vermicomposting, which was also supported by biologically-based maturity indicators.