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.
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.
Whereas the use of biofuels has attracted increasing attention, the aim of this paper is to investigate the possibility of using sewage sludge as biofuel. Preparation of untreated and stabilised sludge with natural additives is described, as well as combusting method applied and experimental results of combusting are presented based on the assessment of composition of emitted pollutants and their concentrations in the exhaust gas. NOx formation in the exhaust gas has been analysed in depth. The results of investigations have shown that the use of dried sewage sludge possesses a positive energy balance. Therefore, the sludge may be used as fuel. The obtained experimental results demonstrate that during combustion, pollutant concentrations vary depending on oxygen content (O2), while formation of nitrogen oxides is strongly influenced by fuel-bound nitrogen. Also, a generalized equation of calculating fuel bound nitrogen conversion into NOx is presented.
The aim of this work was to determine the influence of liming on the process of pyrolysis. Three samples of sludge from two wastewater treatment plants were selected for this study on pyrolysis: sludge without liming and limed sludge from the Central Wastewater Treatment Plant in Ostrava and sludge from the Wastewater Treatment Plant in Sviadnov. The samples had different content of calcite (CaCO3). The limed sludge contained 7% of CaCO3, sludge without liming 3.8% and sludge without liming from WWTP Sviadnov contained 0.5% of calcite. The results of laboratory pyrolysis proved that limed sludge released the maximum amount of carbon - 55.46 %, while sludge without liming from WWTP Sviadnov released only 48.92%. Calcite produces during its decomposition CaO and the product influences the pyrolysis process because it supports cracking of volatile organic compounds