In this work microbiological air pollution at several commune sewage treatment plants (capacity up to 15,000 PE) was investigated. The bioreactors in all plants had a covered construction. The air samples were taken indoors as well as outdoors (both on the windward and leeward side) during different seasons. The samples were collected using the collision method. The presence of indicator organisms in the samples was determined according to the Polish Standards. Identification of individual indicators was performed on solid selective-differentiating substrates. To verify the presence of bacteria from Salmonella, Shigella, coliforms and enterococci species, the colonies observed on the MacConkey substrate were then sifted onto SS and Endo substrates. At all facilities (with one exception) the average CFU for the total number of bacteria and fungi did not exceed 1000/m3, which is the limit set by the Polish Standards for a pollution-free atmospheric air. Bacteria and fungi concentrations, observed at windward and leeward sides of all plants, were relatively low (<100 CFU/m3 and <1000 CFU/m3, respectively) and comparable. A sewage collection point had only a slight impact on the bioaerosol emission. The concentration of microorganisms in the immediate vicinity of covered reactors (aeration chambers) was rather low and remained below the limits sets by the Polish Standards at three facilities. The CFU of individual indicators, measured in rooms accessible for the personnel, was comparable to the CFU in technological rooms. However some indicators, e.g. a number of Actinomycetes, were significantly higher and reached >100 CFU/m3, which means significant air pollution. Similarly, the CFU of hemolytic bacteria had nonzero values. The only place where higher concentrations of bioaerosol were found was the centrifuge room, where digested sludge was dewatered. The number of fungi stayed below the limits there, but the amount of heterotrophic and hemolytic bacteria exceeded the limits and reached the values of ~10000 CFU/m3 and 800 CFU/m3, respectively; it means that the personnel working in this area is exposed to microbiological agents.
The induction of phytoremediation by addition of complex substrates, such as sewage sludge (e.g.
from the food industry), allows for better conditions of plant growth, however, it also increases the risk of chemical compounds leaching to the soil solution. Biogenic compounds occurring in sludge such as nitrogen, organic
carbon and phosphorus when migrating with soil solution down the soil profile can lead to underground water
contamination. The paper assesses the effect of sewage sludge inducted phytoextraction of Zn, Cd and Pb with
the use of Sinapis alba L. (White mustard), Medicago sativa L. (Alfalfa) and Trifolium resupinatum L. (Persian
clover) as well as the migration of biogenic compounds (nitrogen, organic carbon and phosporus) in soil solution. Research was conducted in controlled conditions of a phytotronic chamber in which the lysimetric experiment was carried out in order to monitor the changes of total nitrogen, ammonia, phosphates, organic carbon
and pH every 3 weeks during the 112 days of the entire experiment. Based on the obtained results it was found
that there is no risk of underground water contamination by investigated substances present in sewage sludge,
because there was no indication of increased ammonia and carbon migration to the deeper parts of the soil
profile.The only exception was the migration of nitrogen compounds other than ammonia (possibly nitrates and
nitrites). Due to sewage sludge application the highest concentrations of ammonium nitrogen (211 mgN-NH4
l
-1), total nitrogen (299 mg N l-1) and organic carbon (200 mg TOC l-1) were noted at a layer of 30 cm (from top
of the column/lysimeter) after 3 weeks of the conducted process. With time a decrease of ammonium nitrogen
as well as organic carbon concentration in all columns was noted. There was no indication of phosphates in the
soil solution during the entire experiment, which was due to the high cation exchange capacity of the soil matrix.
The paper presents the results of preliminary studies on the properties of products made by vitrification of waste containing fly ashes from sewage sludge incineration. The performed tests of hazardous substances leached from the ashes, as well as the results of other laboratory tests confirmed the efficacy of vitrification. It has been found that the resulting products (sinters) could be used as a substitute aggregate for road foundations.
The paper presents the investigations aimed at the determination of the effect of time and wavelength of ultrasound field on the value of capillary suction time (CST), sludge thickening and dry matter of the excess sludge subjected to the process of stabilization.
The investigations were carried out on the excess sludge which comes from communal waste treatment plant. The sludge was exposed to ultrasound field, using ultrasound generator with power of 1500 W, frequency of 20 kHz and amplitude 39.42 μm (which corresponded to the amplitude of 100%). Sonication of the sludge was carried out for different amplitudes and sonication times. The non-conditioned sludge and the sludge initially conditioned with ultrasound field were subjected to the process of stabilization in laboratory flasks (V = 0.5 dm3) for the period of 10 days. On each day, sludge thickening and dewatering capacities were determined.
The sludge subjected to the effect of ultrasound field exhibited elevated levels of CST. However, the sonication time had positive effect on the increase in the degree of thickening for each of the amplitudes studied. Also, the process of stabilization positively affected final thickening and dewatering of the sludge.
FA discharged from the wastewater treatment plant were extracted from purifi ed effl uents for the quantitative
and qualitative analysis. The treated sewage from municipal treatment plants was acidifi ed to pH <2 and extracted
with ion exchange resins in a laboratory column. After desorption with NH4
OH, the fulvic acids were condensed
under vacuum and tested for mass performance, UV-VIS light spectra, IR absorption spectra, elementary composition
and other elements. Their structure was analysed and compared to FA present in surface waters and in sewage treated
in other sewage treatment plants based on the authors’ own research and the literature data. The concentration of
FA in the treated sewage was 5.2 mg/L. There is a high interdependence between the IR spectrum analysis in the
visible light and the elementary composition of FA extracted from different environments, confi rming the conclusions
pertaining to the structure and properties of the acids being tested. The longer sewage is subjected to a biological
treatment process, the greater the degree of aromatic condensation and humus maturity of the FA contained within it.
FA contained in the sewage treated in the three biological sewage treatment plants have the ratio A2
/A3
(the ratio of the
absorbance of light with the wavelength of 250 and 300 nm) equal to the value 1.7. There is a high interdependence
between the IR spectrum analysis in the visible light and the elementary composition of FA extracted from different
environments, confi rming the conclusions pertaining to the structure and properties of the acids being tested.
The purpose of the investigation was to assess the suitability of sewage sludge, brown coal and a
mix of sewage sludge and brown coal to be used for fertilizing a light soil with an increased content of lead (I0
)
and slightly contaminated with cadmium (II0
). The subject of tests were soil and plant samples taken from a pot
experiment conducted during the years 2007-2009. The tests determined the effect of the type of fertilization
on the pH and sorption properties of the soil, the contents of heavy metals in the soil and in the plants, and the
volume of crops. The fertilization types applied had an effect of slightly increasing the soil pH. The application
of sewage sludge, brown coal and the mix of sewage sludge with brown coal to the soil resulted in an improvement of the sorption properties of the soil. In the soil treated with sewage sludge and the mix of sewage sludge
with brown coal, an increase in the contents of Cd, Zn and Pb was found. This increase was, however, small and
did not change the degree of soil contamination with heavy metals. In the above-ground parts of plants fertilized
with brown coal the concentration of heavy metals was lower than in biomass from plants cultivated on the
control combination. The application of sewage sludge and the mix of sewage sludge with brown coal generally resulted also in a reduction of metal contents in the above-ground parts of the plants. This was the effect of
enriching the soil with an organic substance that improves the sorption properties. From among the fertilization
combinations tested, the application of either sewage sludge or the mix of sewage sludge with brown coal had
the most favourable effect on the crop volume. It resulted in a twofold increase in the yield compared to the
control combination.
The motivation of this work was to define the reburning potential of sewage sludge gasification gas (syngas). Numerical simulation of co-combustion process of syngas in hard coal-fired boiler has been done. All the calculations were performed using the Chemkin program. Plug-Flow Reactor model was used. The calculations were modelled using GRI-Mech 2.11 mechanism. The highest NO conversions are obtained at the temperature of about 1000-1200 K. The highest reduction efficiency was achieved for the molar flow ratio of syngas equal to 15%. The combustion of hard coal with sewage sludge - derived syngas reduces NO emissions and the amount of coal needed to produce electricity and heat. Advanced reburning, which is a more complicated process gives efficiency of up to 80%. The calculations show that the analyzed syngas can yield better results.
Waste disposal is imposed by the European Union under Treaty of Accession concerning waste management order. One of the waste disposal methods is thermal utilisation. The paper presents an investigation of sewage sludge briquettes used as a fuel in combustion process. The research study was carried out on samples taken from the Municipal Wastewater Treatment Plant in Bochnia. Briquettes with lime were formed. The analysis of the elementary chemical composition of municipal sewage sludge, the composition of the ash and thermogravimetric analysis were carried out. The results indicate that the prepared briquettes had sufficient fuel properties.