Washing is very popular technological operation removing clay particles from aggregates. The amount of mineral washing sludges increases. Besides filling the excavations, there is no common method of their utilization. The usage of sludges from washing aggregates in building ceramics might be environmentally friendly way to utilize them. This paper presents laboratory research on two type of sludges: from dolomite and limestone aggregates washing. Selected properties of sludges such as water content, particle size distribution (sieve and areometric method), chemical composition (XRF), mineral composition (XRD), thermal properties (STA/EGA, dilatometry, heating microscopy) and stability of fired materials during steam exposure were determined. It was found that dolomite sludge contains more clay minerals and less carbonates, it is more finely grained than limestone sludge. Limestone sludge has large fluctuations in water content and has high content of potentially hazardous calcite grains. During heating up to 1300°C of both dried sludges decarbonation and sintering take place. Dolomite sludge softens, melts and flows below 1300°C. After firing sludges at 1000°C material made of limestone sludge is not resistant to steam. The obtained result suggests that dolomite sludge can be used in building ceramics technology without processing as main component of ceramic mass. Limestone sludge have to be ground before its application in building ceramic materials. Results suggest that it can not be used as the main raw material in ceramic masses, but only as an additive.
In the process of extraction and enrichment of coal waste, considerable quantities of waste material are produced, mainly the gangue and coal sludge, considered as waste or raw material. The main directions of the management development of the waste rock are the production of aggregates, the production of energy products and the liquidation works in hard coal mines and the filling of excavations. The paper proposes the extension of these activities to the use of waste material. The possibility of using aggregates or extractive waste to fill open-pit excavations has been proposed, also in areas within the reach of groundwater and the possibility of building insulation layers of waste material and the production of mixtures of hard coal sludge and sewage sludge to produce material with good energy properties. The analysis was based on the author’s own research and literature data related to selected parameters of waste material. This paper presents our own preliminary studies on the amount of combustion heat and the calorific value of coal sludge combined with other wastes such as sewage sludge. The proposed methods and actions are part of the current directions of development, but they allow the extension of the scope of use of both extractive waste and products produced on the basis of gangue or coal sludge. Due to the frequent lack of the stable composition of these materials, their current properties should be assessed each time before attempting to use them. The fact that it is important to continue research to promote existing economic use and to seek new activities or methods has been concluded.
The amount of waste from washing dolomite aggregates increases continuously. Aggregates are washed to remove clayey pollutants.They consist of a large amount of clay minerals and carbonates. Their properties and amount depends on the type of raw material and type of washing technology. Utilization of waste from washing aggregates is common problem and has not been sought out yet. Their usage as the raw material in ceramics might be environmentally friendly way to utilize them. This paper presents technological properties, phase composition and microstructure analysis of materials made of waste sludge from washing dolomite aggregates. Research was divided into three parts: technological properties analysis, phase composition analysis and microstructure analysis. Samples made of waste dolomite sludge were formed in laboratory clay brick vacuum extruder and fired at 900, 1000 and 1100°C. For final materials, apparent density, open porosity, water absorption, compressive strength and durability were examined. Results of technological research suggest the possibility of the application of the waste sludge from washing aggregates in building ceramics technology as bricks materials. Waste sludge from washing dolomite aggregates can be used as the main raw material of building ceramics masses. Without any additional technological operations (e.g. drying or grinding), the material with satisfactory properties was obtained. According to durability results all obtained materials can be used for masonry protected against water penetration and without contact with soil and ground water and also for masonry subjected to passive exposure (F0 – according to the standard EN 771-1).
The new legislative provisions, regulating the trade in solid fuels in our country, draw attention to the need to develop and improve methods and methods of managing hard coal sludge. The aim of the work was to show whether filtration parameters (mainly the permeability coefficient) of hard coal sludge are sufficient for construction of insulating layers in landfills at the stage of their closing and what is the demand for material in the case of such a procedure. The analysis was carried out for landfills for municipal waste in the Opolskie, Śląskie and Małopolskie provinces. For hard coal sludge, the permeability coefficient values are in the range of 10–8–10–11 m/s, with the average value of 3.16 × 10–9 m/s. It can be concluded that this material generally meets the criteria of tightness for horizontal and often vertical flows. When compaction, increasing load or mixing with fly ash from hard coal combustion and clays, the achieved permeability coefficient often lowers its values. Based on the analysis, it can be assumed that hard coal sludge can be used to build mineral insulating barriers. At the end of 2016, 50 municipal landfills were open in the Opolskie, Śląskie and Małopolskie Provinces. Only 36 of them have obtained the status of a regional installation, close to 1/3 of the municipal landfill are within the Major Groundwater Basin (MGB) range. The remaining storage sites will be designated for closure. Assuming the necessity to close all currently active municipal waste landfills, the demand for hard coal sludge amounts to a total of 1,779,000 m3 which, given the assumptions, gives a mass of 2,704,080 Mg. The total amount of hard coal sludge production is very high in Poland. Only two basic mining groups annually produce a total of about 1,500,000 Mg of coal sludge. The construction of insulating layers in landfills of inert, hazardous and non-hazardous and inert wastes is an interesting solution. Such an application is prospective, but it will not solve the problem related to the production and management of this waste material as a whole. It is important to look for further solutions.
Significant quantities of coal sludge are created during the coal enrichment processes in the mechanical processing plants of hard coal mines (waste group 01). These are the smallest grain classes with a grain size below 1 mm, in which the classes below 0.035 mm constitute up to 60% of their composition and the heat of combustion is at the level of 10 MJ/kg. The high moisture of coal sludge is characteristic, which after dewatering on filter presses reaches the value of 16–28% (Wtot r) (archival paper PG SILESIA). The fine-grained nature and high moisture of the material cause great difficulties at the stage of transport, loading and unloading of the material. The paper presents the results of pelletizing (granulating) grinding of coal sludge by itself and the piling of coal sludge with additional material, which is to improve the sludge energy properties. The piling process itself is primarily intended to improve transport possibilities. Initial tests have been undertaken to show changes in parameters by preparing coal sludge mixtures (PG SILESIA) with lignite coal dusts (LEAG). The process of piling sludge and their mixtures on an AGH laboratory vibratory grinder construction was carried out. As a result of the tests, it can be concluded that all mixtures are susceptible to granulation. This process undoubtedly broadens the transport possibilities of the material. The grain composition of the obtained material after granulation is satisfactory. Up to 2 to 20 mm granules make up 90–95% of the product weight. The strength of the fresh pellets is satisfactory and comparable for all mixtures. Fresh lumps subjected to a test for discharges from a height of 700 mm can withstand from 7 to 14 discharges. The strength of the pellets after longer seasoning, from the height of 500 mm, shows different values for the analyzed samples. The values obtained for hard coal sludge and their blends with brown coal dust are at the level from 4 to 5 discharges. The strength obtained is sufficient to determine the possibility of their transport. At this stage of the work it can be stated that the addition of coal dust from lignite does not cause the deterioration of the material’s strength with respect to clean coal sludge. Therefore, there is no negative impact on the transportability of the granulated material. As a result of mixing with coal dusts, it is possible to increase their energy value (Klojzy-Karczmarczyk at al. 2018). The cost analysis of the analyzed project was not carried out.
The article describes problems related to intensiﬁcation of energy production at a sewage treatment plant. The authors analyze anaerobic co-digestion of sludge from a water treatment plant and sewage treatment plant. The authors proposed a methodology of the research and analyzed the preliminary results, which showed that co-digestion of sewage and water sludge enhanced biogas production. The authors hope that the results of the study will provide a basis for development of methodology for sludge control and disposal.
Recent studies have shown that over half of the world’s population lives in urban areas, with the number of people living in slums growing by over 20 million per year and people living in urban areas lacking access to adequate sanitation. This study presents a review of the challenges facing fecal sludge management (FSM). A globally relevant issue in developing urban centers, especially in selected developing countries in West Africa was discussed. Some key ﬁndings of the review are that effective sanitation in developing areas depends on the chain of services and that one of the largest problems in sanitation is FSM. This study presents the initial steps toward understanding the main issues involving FSM in developing cities of West Africa. Results are intended to be used as a support for decisions on policies, strategies for FSM, and investments for improved treatment facilities in the region. The study suggests that governments and private sector organizations should develop adequate measures for handling fecal sludge.
The present paper describes a cycle, which may be applied in sewage treatment plants as a system to convert biological waste into process heat and electricity. In sludge stabilization processes anaerobic fermentation acts as the source of methane, which can be used then to generate heat and electric current in gas turbines. Products of high-temperature oxidation can be utilized in organic Rankine cycles to generate electric power. Waste heat is used for heating the fermenting biomass. Energy balance equations mentioned in the thesis: organic Rankine cycle, regenerative gas turbine engine, anaerobic sludge stabilization system.
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
The primary objective of the present study was to determine the seasonal dynamics of ciliates in activated sludge. Studies were carried out in order to verify the hypothesis that fertility of a habitat may significantly influence the seasonal dynamics of the abundance of ciliates, as well as the number and intensity of correlations between physic-chemical parameters and ciliates. It seems that the values of numbers of ciliates were seasonally changeable. The highest numbers of ciliates were found in spring and summer, however the lowest numbers of ciliate communities were noted in winter. The studies showed that protozoa community is determined by ammonia mainly in summer. In spring and winter additional factors may be important. Probably suspended solid, total organic carbon and concentration of appropriate food (bacteria and flagellates) are the major regulator of abundance of ciliates.
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 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 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 essence of the methane fermentation course is the phase nature of changes taking place during the process. The biodegradation degree of sewage sludge is determined by the effectiveness of the hydrolysis phase. Excess sludge, in the form of a ﬂocculent suspension of microorganisms, subjected to the methane fermentation process show limited susceptibility to the biodegradation. Excess sludge is characterized by a signiﬁcant content of volatile suspended solids equal about 65 ÷ 75%. Promising technological solution in terms of increasing the efﬁciency of fermentation process is the application of thermal modiﬁcation of sludge with the use of dry ice. As a result of excess sludge disintegration by dry ice, denaturation of microbial cells with a mechanical support occurs. The crystallization process takes place and microorganisms of excess sludge undergo the so-called “thermal shock”. The aim of the study was to determine the effect of dry ice disintegration on the course of the methane fermentation process of the modiﬁed excess sludge. In the case of dry ice modiﬁcation reagent in a granular form with a grain diameter of 0.6 mm was used. Dry ice was mixed with excess sludge in a volume ratio of 0.15/1, 0.25/1, 0.35/1, 0.45/1, 0.55/1, 0.65/1, 0.75/1, respectively. The methane fermentation process lasting for 8 and 28 days, respectively, was carried out in mesophilic conditions at 37°C. In the ﬁrst series untreated sludge was used, and for the second and third series the following treatment parameters were applied: the dose of dry ice in a volume ratio to excess sludge equal 0.55/1, pretreatment time 12 hours. The increase of the excess sludge disintegration degree, as well as the increase of the digestion degree and biogas yield, was a conﬁrmation of the supporting operation of the applied modiﬁcation. The mixture of reactant and excess sludge in a volume ratio of 0.55/1 was considered the most favorable combination. In relation to not prepared sludge for the selected most favorable conditions of excess sludge modiﬁcation, about 2.7 and 3-fold increase of TOC and SCOD values and a 2.8-fold increase in VFAs concentration were obtained respectively. In relation to the effects of the methane fermentation of non-prepared sludge, for modiﬁed sludge, about 33 percentage increase of the sludge digestion degree and about 31 percentage increase of the biogas yield was noticed.
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 study presents the manners of determination of the Darcy friction factor λ for a homogenous hydromixture of alum sludge of varied hydration and temperature for the laminar flow zone. The rheological evaluation of the hydromixture as a viscoplastic body has been conducted with use of measurements of viscosity. The curves of flow were approximated with use of the generalized Vočadlo model. The Darcy friction factor λ of the pipeline was determined with use of the non-dimensional criterion λ(Regen) and λ(Re, He).
Improving the effects of hydrolysis on waste activated sludge (WAS) prior to anaerobic digestion is of primary importance. Several technologies have been developed and partially implemented in practice. In this paper, perhaps the simplest of these methods, alkaline solubilization, has been investigated and the results of hydrolysis are presented. An increase to only pH 8 can distinctively increase the soluble chemical oxygen demand (SCOD), and produce an anaerobic condition effect favorable to volatile fatty acids (VFA) production. Further increases of pH, up to pH 10, leads to further improvements in hydrolysis effects. It is suggested that an increase to pH 9 is sufficient and feasible for technical operations, given the use of moderate anti-corrosive construction material. This recommendation is also made having taken in consideration the option of using hydrodynamic disintegration after the initial WAS hydrolysis process. This paper presents the effects of following alkaline solubilization with hydrodynamic disintegration on SCOD
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.
Primary or secondary sewage sludge in medium and large WWTP are most often processed by anaerobic digestion, as a method of conditioning, sludge quantity minimization and biogas production. With the aim to achieve the best results of sludge processing several modifications of technologies were suggested, investigated and introduced in the full technical scale. Various sludge pretreatment technologies before anaerobic treatment have been widely investigated and partially introduced. Obviously, there are always some limitations and some negative side effects. Selected aspects have been presented and discussed. The problem of nitrogen has been highlighted on the basis of the carried out investigations. The single and two step - mesophilic and thermophilic - anaerobic waste activated sludge digestion processes, preceded by preliminary hydrolysis were investigated. The aim of lab-scale experiments was pre-treatment of the sludge by means of low intensive alkaline and hydrodynamic disintegration. Depending on the pretreatment technologies and the digestion temperature large ammonia concentrations, up to 1800 mg NH4/dm3 have been measured. Return of the sludge liquor to the main sewage treatment line means additional nitrogen removal costs. Possible solutions are discussed.
Sewage sludge (municipal, or industrial) treatment is still a problem in so far that it is not satisfactorily resolved in terms of cost and final disposal. Two common forms of sludge disposal are possible; the first being direct disposal on land (including agriculture) and the second being incineration (ash production), although neither of these methods are universally applied. Simplifying the issue, direct sludge disposal on land is seldom applied for sanitary and environmental reasons, while incineration is not popular for financial (high costs) reasons. Very often medium and large wastewater treatment plants apply anaerobic digestion for sludge hygiene principles, reducing the amount to be disposed and for biogas (energy) production. With the progress in sewage biological treatment aiming at nutrient removal, primary sludge has been omitted in the working processes and only surplus activated sludge requires handling. Anaerobic digestion of waste activated sludge (WAS) is more difficult due to the presence of microorganisms, the decomposition of which requires a relatively long time for hydrolysis. In order to upgrade the hydrolysis effects, several different pre-treatment processes have already been developed and introduced. The additional pre-treatment processes applied are aimed at residual sludge bulk mass minimization, shortening of the anaerobic digestion process or higher biogas production, and therefore require additional energy. The water-energy-waste Nexus (treads of) of the benefits and operational difficulties, including energy costs are discussed in this paper. The intensity of pre-treatment processes to upgrade the microorganism’s hydrolysis has crucial implications. Here a low intensity pre-treatment process, alkalisation and hydrodynamic disintegration - hybrid process - were presented in order to achieve sufficient effects of WAS anaerobic digestion. A sludge digestion efficiency increase expressed as 45% biogas additional production and 52% of the total or volatile solids reduction has been confirmed.
Osier (salix viminalis) is a promising energy crop for the growing bioenergy purposes in Ukraine. It is unpretentious to the conditions of growth, marked with simplicity of cultivation technology, well-withdrawn for fertilization. Sewage sludge, due to its chemical composition and high content of organic matter, can be successfully used to fertilize the willow. The calculations of bioenergetic and economic efficiency showed that application of sewage sludge and compost with sawdust and straw in a ratio of 3: 1 at osier is marked with a high effect. In the studies performed in conditions of Ukraine’s Precarpathians on sod-podzolic soils we found that the highest biomass output and, therefore, gross energy per unit of area in agrocenoses of osier provided the application of fresh sewage sludge at a rate of 80 t / ha. In this option the dry biomass output made 39.4 t / ha, gross energy with the yield - 1,580 GJ / ha, the costs of energy generation - 6.2 UAH / GJ, the costs of gross output - 17.8 thousand UAH / ha, the rate of energy efficiency - 1.69. However, the highest rates of economic and bioenergetic efficiency after the fourth year of the willow vegetation we observed when the sewage sludge compost with straw of grain crops at a doze 40 and 60 t / ha was applied. In these variants the lowest cost of the biomass production was obtained (at the level 109 - 111 UAH / ton), the cost of the received energy from the biomass (5.6 - 5.7 UAH / GJ), the highest profitability value (97 - 101%) and the best performing of energy efficiency coefficient - 1.85 - 1.89.