Agnieszka Rorat

Sewage sludge disposal strategies for sustainable development

ABSTRACT The main objective of the present review is to compare the existing sewage sludge management solutions in terms of their environmental sustainability. The most commonly used strategies, that include treatment and disposal has been favored within the present state‐of‐art, considering existing legislation (at European and national level), characterization, ecotoxicology, waste management and actual routs used currently in particular European countries. Selected decision making tools, namely End‐of‐waste criteria and Life Cycle Assessment has been proposed in order to appropriately assess the possible environmental, economic and technical evaluation of different systems. Therefore, some basic criteria for the best suitable option selection has been described, in the circular economy “from waste to resources” sense. The importance of sewage sludge as a valuable source of matter and energy has been appreciated, as well as a potential risk related to the application of those strategies. HighlightsEnvironmental sustainability in sewage sludge management.Investigation of eco‐innovations in wastewater treatment.Assessment of ecological consequences of sewage sludge disposal.

The presence of contaminations in sewage sludge – The current situation

Abstract Sewage sludge/biosolids are by-wastes of municipal and industrial wastewater treatment. As sources of nutrients (C, N, P) they are widely used in intensive farming where large supplementation of organic matter to maintain fertility and enhance crop yields is needed. However, according to the report of European Commission published in 2010, only 39% of produced sewage sludge is recycled into agriculture in the European Union. This situation occurs mainly due to the fact, that the sewage sludge may contain a dangerous volume of different contaminants. For over decades, a great deal of attention has been focused on total concentration of few heavy metals and pathogenic bacteria Salmonella and Escherichia coli. The Sewage Sludge Directive (86/278/EEC) regulates the allowable limits of Zn, Cu, Ni, Pb, Cd, Cr and Hg and pathogens and allows for recovery of sludge on land under defined sanitary and environmentally sound conditions. In this paper, a review on quality of sewage sludge based on the publications after 2010 has been presented. Nowadays there are several papers focusing on new serious threats to human health and ecosystem occurring in sewage sludge – both chemicals (such as toxic trace elements – Se, Ag, Ti; nanoparticles; polyaromatic hydrocarbons; polychlorinated biphenyl; perfluorinated surfactants, polycyclic musks, siloxanes, pesticides, phenols, sweeteners, personal care products, pharmaceuticals, benzotriazoles) and biological traits (Legionella, Yersinia, Escherichia coli O157:H7).

Biochar amendment for integrated composting and vermicomposting of sewage sludge – The effect of biochar on the activity of Eisenia fetida and the obtained vermicompost

Sewage sludge derived biochar (SSDB) was used as a supplementary material for municipal sewage sludge (SS) and wood chips mixtures (WC) treated by combined composting and vermicomposting. SSDB added to the mixture before composting resulted in significantly higher reproduction rate: on week 4 the number of cocoons increased by 213% when compared to the mixture with no biochar. On week 6 the average number of juveniles increased 11-fold in the mixture with biochar added before composting and 5-fold in the mixtures with biochar added after composting when compared to the mixture with no biochar. Biochar added before composting reduced bioavailability of Cd and Zn to E. fetida. The biochar-added vermicomposts showed good fertilizing properties except for elevated concentrations of Cr. The pH of all vermicomposts was in the range of 5.27-5.61. The obtained vermicomposts can be used as a growing medium for horticultural purposes or as an amendment in calcareous soils.

Coelomocyte-derived fluorescence and DNA markers of composting earthworm species

Supravital species identification of morphologically similar syntopic earthworms inhabiting dung and compost heaps or those from commercial cultures is difficult. The aim of the studies was to find out non-invasive species-specific markers for proper segregation of earthworm species from a dense mixed colony of waste decomposers. Worms were segregated according to external characteristics into Eisenia andrei, Eisenia fetida, and Dendrobaena veneta, and left for reproduction and analysis of non-invasively retrieved coelomocyte-containing coelomic fluid and/or species-specific partial sequences of cytochrome c oxidase subunit I (COI) gene in DNA extracted from amputated tail tips of adults and their offspring. Flow cytometric analysis of coelomocyte samples revealed that amount of nuclear DNA increases in order D. veneta ≪ E. andrei < E. fetida, and intensity of eleocyte-derived fluorescence is lower in D. veneta than in Eisenia spp. Spectrofluorimetry of coelomocyte lysates revealed that the amount of eleocyte-stored riboflavin is significantly lower in coelomocyte lysates from D. veneta than from Eisenia spp., and the emission peak of X-fluorophore is much more distinct in D. veneta than in Eisenia spp. Coelomic fluid of E. andrei exhibits a very distinct spectra of MUG fluorophore which are absent in D. veneta and in the majority of E. fetida, while some E. fetida possess MUG-like fluorophore. Sequences of the COI gene in the DNA of the worms from the mixed colony and their offspring confirmed species identity. In conclusion, species-specific coelomocyte-derived markers may be a useful complement to morphological and DNA-based taxonomy during studies on syntopic earthworms.

Dermal exposure of Eisenia andrei earthworms: Effects of heavy metals on metallothionein and phytochelatin synthase gene expressions in coelomocytes

Parameters such as total number of coelomocytes, riboflavin content in coelomocytes, expression of genes implied in metal homeostasis, and detoxification mechanisms can be used as biomarkers to assess the impact of metals on annelids. Defense biomarkers (detoxification gene expressions and coelomocyte parameters) were investigated in the ecotoxicologically important species Eisenia andrei following in vivo exposure to 5 different metals (zinc, copper, nickel, lead, and cadmium) at known concentrations. Coelomocyte numbers and riboflavin content were not affected by metallic exposure, but metal-specific gene expression variations were evidenced.

Copper toxicity and date palm (Phoenix dactylifera) seedling tolerance: Monitoring of related biomarkers

Date palm (Phoenix dactylifera) seeds were exposed to different copper (Cu) solutions to examine plant stress responses. Low Cu concentrations (0.02 and 0.2 mM) caused an increase of seed germination, whereas higher Cu amounts (2 mM) significantly inhibited seed germination, delayed hypocotyl elongation, increased seedling mortality, and reduced the germination index by more than 90%. Metal-related toxicity symptoms appeared after 15 d of 2 mM of Cu exposure. Biochemical activities such as amylase activity and redox balance elements were examined to study the relationship between external Cu amount and internal plant response. The present study showed that amylolytic activity was dose- and time-dependent. Likewise, H2 O2 production increased after exposure to Cu, which was correlated with thiobarbituric acid reactive substance (TBARS) accumulation. Furthermore at low Cu concentrations, superoxide dismutase (SOD) and catalase (CAT) activities increased, suggesting that date palm seed stimulated its metal homeostasis networks. However, the highest cupric ion amounts increased cell oxidant accumulation and reduced enzyme production. Gene expression level measures of P. dactylifera phytochelatin synthase (Pdpcs) and P. dactylifera metallothionein (Pdmt) encoding genes have been carried out to investigate the implication of PdPCS and PdMT proteins in Cu homeostasis and/or its sequestration. Phoenix dactylifera metallothionein induction reached a peak after 30 d of exposure to 0.2 mM of Cu. However, it was down-regulated in plants exposed to higher Cu concentrations. In the same conditions, Pdpcs was overexpressed during 1 mo of exposure before it decreased thereafter. These observations provide a new insight into date palm cell response to Cu, a metal that can be toxic but that is also an essential element. Environ Toxicol Chem 2018;37:797-806.

Eco-Innovations in Sustainable Waste Management Strategies for Smart Cities

With waste management strategies constrained by strict laws and ecological requirements, new holistic approaches have attracted great interest. The main focus is now on converting organic wastes into renewable energy sources or “biosoils”. Biological waste disposal alternatives have a huge environmental potential, coming as a substitute for expensive, hazardous methods, such as landfillling or incineration. Their possible impact on the environment can be assessed from the ecological, economical and sociological point of view using decision-making tools, e.g., Life Cycle Assessment (LCA), which seek to identify the best practices for a sustainable development of smart cities.

Bacterial ACC Deaminase Activity in Promoting Plant Growth on Areas Contaminated with Heavy Metals

The objective of this study was to explore the possible improvement of plant growth using the activity of the bacterial enzyme ACC (1-aminocyclopropane-1-carboxylate) deaminase (endophytes and rhizobacteria). The beneficial effect of ACC deaminase activity was tested on the plants growing under stress conditions (high concentrations of heavy metals: cadmium, lead, zinc in the soil). The bacteria were isolated from three plants species: Festuca rubra L., Agrostis capillaris L., Arabidopsis thaliana L. Heynh, acquired from the area contaminated with heavy metals. The strains with the highest ACC deaminase activity were used to prepare a bacterial consortium and inoculate the plants. It has been shown that inoculation of plants with ACC producing bacteria has a positive effect on their growth under stress conditions. The bacterial entophytes strains showed a higher activity of ACC deaminase, which resulted in a higher biomass growth of inoculated plants. The PGPB bacteria may limit the toxicity of harmful ions and thus the increase the adaptive properties of plants. Moreover, it was discovered that the bacteria mainly belonging to genus Bacillus and Pseudomonas had the highest ACC deaminase activity in the environment contaminated with multiple heavy metals. The use of selected microorganisms and plants will provide results in an increasing efficiency of phytoremediation.

Vermicomposting as an Alternative Way of Biodegradable Waste Management For Small Municipalities

The aim of the study was to assess the usefulness of vermicomposting as a method of bioconversion of organic wastes, inter alia, sewage sludge, biodegradable fraction of municipal solid wastes and green wastes. Vermicomposting is a biological process in which earthworms are employed to cooperate with microorganisms in order to convert organic wastes into a valuable product. It is considered as a relatively low cost and environmentally-friendly method of waste treatment. Nevertheless, as each biotechnology, the process is limited to some physical, chemical and biological parameters. In this study, sewage sludge coming from medium-sized wastewater treatment plant was mixed with mown grass, sawdust and organic fraction of municipal wastes and vermicomposted for 5 weeks with Eisenia fetida and Eisenia andrei as main actors. The scope of the research was to 1)assess the influence of E. fetida and E.andrei composting earthworms on the physical and chemical properties of the product; 2) changes of concentration of selected heavy metals and their available forms in compost during the process, 3) the effects of substrates on earthworms survival and reproduction. Selected earthworm species had shown a high tolerance to the contaminants present in sewage sludge and a positive impact on the quality of the product was noted. Vermicomposting enhances decomposition of organic matter, leads to decrease in C/N ratio and pH, and changes the availability of some heavy metals and its total content in substratum. Experimental medium led earthworms to increase body weight due to the presence of large amount of organic matter, while the reproduction was importantly reduced. Vermicomposting can be considered as a method of treatment of solid wastes, mainly in the case of small municipalities.