Traditional brick production relies heavily on natural clay, the availability of which is gradually declining due to increasing demand. This study explores the potential of sewage sludge ash (SSA) as a partial replacement for clay, aiming both to reduce the extraction of natural raw materials and to address SSA disposal challenges. SSA used in this research was obtained through gasification of sewage sludge in an innovative pilot rotary kiln reactor designed for hydro-energy production. As part of a circular waste approach, SSA was incorporated at 5

Sewage sludge, as a by-product of wastewater treatment, represents a significant cost factor in the operation of wastewater treatment plants and accounts for up to 50% of total costs. As sewage sludge still contains a high proportion of water after the basic treatment processes (thickening, stabilization and dewatering), sludge drying helps to reduce further treatment and disposal costs. Conventional drying methods are associated with high energy consumption, making solar drying a more cost-effective alternative. This paper analyzes the economic aspects of constructing a sewage sludge solar drying facility with the help of an expert system based on neural networks. The system considers a range of parameters (plant capacity, transport distance, transport and treatment costs, etc.) to assess the values of the investment as well as the operation and maintenance costs. The analysis was carried out using NeuralTools (Lumivero). Two main options for sludge disposal were investigated: treatment at a regional center (with the sub-options of own or outsourced transport) and handing over of sludge to another legal entity. In total, five neural network models were developed based on the input load (from 75 to 10,000 t/year and from 10,000 to 20,000 t/year) and transport method (own or outsourced transport), resulting in an analysis of over 670,000 scenarios. The key output variable was the net present value of costs over a 30-year period. The results demonstrated high model accuracy (error < 5%) and allowed a comparison of the profitability of constructing a sewage sludge solar drying facility with alternative methods of sludge disposal, in particular with the transport and disposal of the dewatered sludge.

The growing amounts of sewage sludge (SS) and water pollution caused by heavy metals are major environmental concerns. This study addresses both issues by investigating the potential of biochar derived from SS gasification at an experimental plant as an effective adsorbent for the removal of selected heavy metals, cadmium, chromium, copper, and lead, from synthetic wastewater. A Box–Behnken design was used to determine the influence of the biochar mass, initial heavy metal concentration, pH, and time on the heavy metal removal. For the statistical analysis, 104 experiments were performed. The pristine SS biochar demonstrated an adsorption capacity reaching up to 46.64 mg/g for Cd, 43.89 mg/g for Cr, 42.42 mg/g for Cu, and 72.66 mg/g for Pb from single-component synthetic solutions in acidic-to-neutral conditions, with an over 99% removal efficiency for all four heavy metals under optimal conditions. The removal of all the tested metals followed pseudo-second-order kinetics, with Cd fitting the Langmuir model and Pb, Cr, and Cu fitting the Freundlich model. This paper also provides suggestions for further research focused on the multiple uses of biochar as an adsorbent and later as a substitute material in the construction industry, aiming to achieve an integrated approach and maximizing the overall sustainability of wastewater treatment and waste management by utilizing waste as a resource.

Sewage sludge (SS), once considered waste, is now recognized as a valuable raw material with potential for reuse and recycling, aligning with the European Union's push towards a circular economy. This study explores the utilization of dry SS as an organic additive in fired clay bricks, focusing on efficient drying methods like microwaves (MWs). MW drying offers advantages such as significantly reduced drying times compared to conventional methods and the elimination of pathogenic microorganisms. In this research, MW-dried SS (MDSS) was compared with conventionally dried SS (CDSS) in the production of fired clay bricks, with a maximum SS content of 20 %. While an increase in SS mass had a negative impact on brick quality, bricks using MDSS exhibited improved mechanical and durability properties compared to CDSS. Evaluation of the bricks included standard tests like compressive strength, water absorption and initial rate of absorption. The greatest improvements were observed at the lowest MDSS content (5 %), with a 35.35 % improvement in compressive strength, a 11.11 % reduction in water absorption, and a 65.30 % reduction in the initial rate of absorption (IRA). In contrast, at the highest MDSS content (20 %), the improvements were less pronounced, with a 0.96 % improvement in compressive strength, a 6.66 % reduction in water absorption, and a 2.32 % reduction in the IRA. Additionally, assessments of heavy metal content, mineralogical analysis of powdered SS brick samples, soluble salt content determination, leaching tests, ecotoxicity assay using Vibrio fischeri bacteria (a common bioindicator organism), and radioactivity determination were conducted. Surprisingly, ecotoxicity tests indicated toxicity for the sample group of MDSS ZG bricks and control brick. However, additional leaching tests, considering the method's sensitivity, refuted this finding and indicated inert behaviour. Total radioactivity tests generally aligned with typical fired clay concentrations, remaining well below EU maximum limits.

The aim of this study is to determine the impact of wood biomass ash (WBA) as a substitute for part of the clay on the properties of bricks and to validate laboratory tests in collaboration with brick manufacturers to ensure consistent product quality at industrial production level. Six samples of WBA from different locations in the Republic of Croatia were taken for testing purposes. This work examines the properties of bricks in which WBA partially replaces clay, employing the hand moulding method for brick preparation. Bricks are shaped into both disc and prism forms, allowing us to assess the impact of WBA on various properties such as shrinkage during drying and firing, compressive strength, and water resistance properties, including water absorption by boiling, absorption, and saturation coefficient. The results indicate that even a minimal substitution of only 3

The derived gasification SS (sewage sludge) biochar product is porous and inexpensive, so it has a potential to be used as an adsorbent in wastewater treatment: in the removal of nutrients (phosphate and ammonium), heavy metals, or some pesticides. SS biochar has also shown the potential to replace part of the original raw materials in the construction industry. The final goal of the broader research is to examine the possibility of multiple use of SS biochar, firstly in wastewater treatment and subsequently in the production of innovative building materials and products.

The derived pyrolysis or gasification biochar products are porous, inexpensive and have a potential to be used as an adsorbent for wastewater treatment. This study examines the effectiveness of removing heavy metals (cadmium (Cd) and lead (Pb)) and nutrients in the form of ammonium (NH4+) and phosphate (PO43-) from synthetic wastewater using biochar obtained by a special process of gasification of sewage sludge in a pilot plant. Batch adsorption experiments were carried out to determine the adsorption capacity of biochar for selected pollutants. The results of PO43-and NH4+ removal at the pH of the initial solutions, show a reduction of PO43-concentration by over 20% and NH4+ concentration by 8% within 24 hours, which, expressed in absolute quantities of the removed pollutant, was 215 mg/L for PO43-, and 115 mg/L for NH4+. When analyzing the removal of Cd2+ and Pb2+, experiments were performed at the initial pH (3.1-3.2), and then with an adjusted value of pH=7, which resulted in significantly better results for the removal of these cations within 24 h: over 20% of Cd2+ and almost 50% of Pb2+.

Ultrasonic technology can be used in various branches of industry, but its use in water and wastewater treatment has not yet been sufficiently researched. The aim of this paper is to investigate the application of ultrasound in wastewater treatment, with a focus on oily wastewater. In the experimental study, ultrasound was combined with electrocoagulation to remove mineral oil and it was shown that this treatment increased mineral oil removal from 15% to 50% compared to electrocoagulation alone.

Electrochemical wastewater treatment technologies are increasingly being used in practice, and the combination of electrocoagulation with advanced oxidation processes has been shown to increase treatment efficiency. The treatment of oily wastewater produces electrocoagulated metal sludge (EMS). In this work, the possibility of using different ratios of EMS produced during oily wastewater treatment was investigated. EMS was dried conventionally in an oven at 105 °C and used as a partial substitute for clay in the manufacture of laboratory bricks. The main research objectives of this study were to examine the possibility and justification of introducing EMS in brick production. The results show that an increase in the proportion of EMS in the manufacturing of bricks leads to a deterioration in the quality of the bricks. Bricks with an addition of 1 wt% and 5 wt% EMS showed the best properties. The loss on ignition (LOI), compressive strength, boiling water absorption and initial water absorption were determined at 5.7%; 49 N/mm2, 16%, 14 g/min/200 cm2, 15% for modified bricks with 1 wt% EMS and 6.3%, 48 N/mm2, 20%, 15 g/min/200 cm2 for modified brick with 5 wt%.

Acetamiprid, a neonicotinoid insecticide widely employed in agricultural practices, has garnered attention due to its persistence, toxicity, and potential adverse effects on non-target organisms. Traditional wastewater treatment processes often prove inadequate in efficiently removing pesticides necessitating the exploration of more adequate remediation technologies. Electrochemical methods offer a promising avenue for the degradation and removal of pesticide contaminants from aqueous environments. In this study, the response surface methodology was used to investigate the possibility of electrochemical removal of acetamiprid from water. For statistical experimental design, central composite design was used, and three factors were studied - electrode material (Fe, Cu, Al), treatment time (15, 37.5, 60 min) and applied current (4, 9, 14 A). Electrochemical treatment proved to be a viable option with efficiencies over 50%.

The discharge from ammunition factories typically contains a cocktail of pollutants, including heavy metals, organic compounds, and suspended solids, posing potential ecological risks if left untreated. Electrocoagulation (EC) emerges as a promising alternative for the remediation of such challenging effluents. EC, a robust electrochemical process, involves the dissolution of sacrificial electrodes to induce coagulation and subsequent removal of contaminants through processes such as precipitation, flocculation, and electroflotation. This paper presents an investigation into the application of electrocoagulation for the treatment of ammunition factory wastewater. Using a simple set-up, two electrode materials, aluminum and iron, were tested, as well as their combinations. The influence of the initial pH value of the solution was, also, investigated. Treatment time varied from 5 to 30 minutes and electric current of 3 A was used in all of the experiments. 50% of COD and almost complete heavy metal removal was achieved in 30 minutes, indicating that electrocoagulation could be a promising technique for the remediation of heavily contaminated wastewaters.

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The paper examines the efficiency of a hybrid electrochemical procedure with electrodes made of iron, aluminium, stainless steel and carbon in the treatment of oily wastewater of mineral origin. The impact of current intensity on the efficiency of the applied treatment process is also examined. Oily wastewater in the paper is generated in a syngas treatment system (wet scrubber) within the pilot gasifier of sludge from a wastewater treatment plant. In order to optimise the process, the paper examined the impact of electrode types connected in series and their combinations on the efficiency of the removal of individual water quality indicators. The purpose of the examination was to achieve a satisfactory efficiency of the removal of total hydrocarbons, mineral oils, chemical oxygen demand (COD) and total organic carbon (TOC) from oily wastewater. The wastewater that is the subject of this research is characterised by high concentrations of COD (2200 mg/L), total hydrocarbons (150 mg/L) and a pH value of about 9.0. Stainless steel electrodes proved very efficient in the removal of COD (over 70%) and total hydrocarbons (over 65%). Iron and aluminium electrodes showed a lower efficiency, i.e. 25% and 11%, respectively. A serial connection of treatment phases (reactions) using stainless steel, iron and aluminium electrodes connected in series resulted in the removal of total hydrocarbons of 99.9%, COD of 96% and TOC of 73%.

The aim of this paper is to analyse sewage sludge production at the level of Medimurje and Varazdin counties with economic analysis of acceptable technical/technological solutions for sludge management routes. The topic is very broad, so the focus was placed on four variants of sludge disposal, which were determined by preliminary analysis to be the most applicable for the area in question. These are: 1) disposal of sewage sludge in agriculture, 2) incineration of sludge in a central mono-incinerator, 3) composting for the area of Varazdin County and at the same time use of sludge reed beds for the area of Medimurje County, and 4) export of sludge outside the state borders. Based on the analysis carried out for the described four variants, sludge incineration in a regional mono-incinerator turned out as the economically most advantageous solution, while the variant that includes disposal of sludge in agriculture has showed as the most expensive one. The last one also showed the largest range of costs uncertainties, but the mentioned facts are greatly influenced by unfavourable legislation, the changes of which in a more rational direction would greatly contribute to the greater competitiveness of this variant. Overall, taking into account the lowest cost and uncertainties in the predicted unit costs, the sludge composting in the Varazdin County and the construction of a reed beds for the Medimurje County, turned out to be the optimal variant. This solution is also the one that was ultimately adopted in practice.

Sewage sludge management is a current problem worldwide because of its increasing quantities and the presence of contaminants.Its sustainable handling should be socially acceptable, cost-effective method that meets requirements of the efficient recycling of resources and ensures that harmful substances are not transferred to humans or the environment.This paper provides an overview of the most used procedures of sludge treatment and disposal in relation to the basic environmental impacts: the content of heavy metals and pathogenic microorganisms when it is used in agriculture and harmful gases when thermal treatment procedures are opted.LCA is a holistic methodology allowing for the analysis of environmental impacts of different sludge treatment and disposal/use options.The use of sludge in agriculture implies the quality classification of sludge, depending on which the limits of application are determined, differing significantly between countries.Thermal treatment technologies are environmentally risky regarding negative impact on the air, and thus on human health.Higher combustion temperatures and more advanced flue gas treatments guarantee better results.Gasification is a process with higher temperatures where emissions of harmful gases are lower compared to other thermal treatment processes.Energy recovery can significantly reduce both environmental and economic burdens.There is an ongoing development of new methods for the agriculture use of sludge and its thermal treatment whose application is expected in the future resulting in updated limit values of heavy metals and pathogens content in sludge, as well as limit emissions of pollutants into the air when thermal treatment is opted.

The gasification of sewage sludge (SS) was studied in a semi-industrial pilot plant consisting of a rotary kiln reactor. The gasification process was preceded by drying the SS in an integrated tubular rotating structure with built-in worm conveyors, to increase the dry matter (DM) content in the SS (> 90 wt.%). The released hydrogen-rich syngas from the gasification process of SS had low heating value (LHV) of approximately 8.83 MJ N-1 m(-3) (equal to 2.45 kWh N-1 m(-3)) due to the high content of combustible gases H-2 (41.5 vol.%) and CH4 (3.2 vol.%). Also investigated was the incorporation of sewage sludge ash (SSA) generated in the process of gasification as a partial substitute for clay in the production of clay bricks. Amounts of 5 wt.%, 10 wt.%, 20 wt.% of clay were replaced by SSA. By incorporating SSA at 5 wt.%, the new brick product achieved 4.5 % higher compressive strength compared to the control brick.

In this paper the effect of ultrasound and electrocoagulation on the removal of manganese from synthetic wastewater was investigated. It was shown that 20 kHz ultrasound alone is not very efficient for manganese removal, but it enhances the efficiency of electrocoagulation. It was also shown that settling has a great effect on the electrocoagulation process because it stabilizes the flocs. A total of four laboratory-scale experiments were conducted, and the optimal experiment included 10 minutes of ultrasound and 10 minutes of electrocoagulation with iron electrodes. Under these conditions, 89.0 % of the manganese was removed with an operating cost of 0.13 EUR/mg Mn. Adding the cost of replacing the immersed ultrasonic probe, the total operating cost increased 3000-fold, making the immersed ultrasonic probe method unviable for large-scale application.

Modeling pumping and consumption behavior in water supply requires the analysis of numerous input and computational data, whose functional dependence is usually not easy to determine. This paper analyzes these dependencies and provides a software solution (program code) that, based on the known maximum daily consumption and its pattern, determines the minimum required operating volume of the water tank with the associated regime of pumping water from the source into the water tank (start and duration of continuous pumping). By simplifying existing "manual" calculations created program adapts them to the needs of scientists, but also engineers involved in water supply system design and operational activities related to changes in the operation of pumping stations and water tank, to minimize capital costs (construction of a water tank) and operating costs (pumping). Therefore, the created program assumes for each hour of the day the start of pumping water into the water tank with different durations (1-24 hours), which gives a total of 576 different options and indicates the optimal solution (or solutions in the case of finding several equivalent options) the one for which the minimum required volume is obtained. The functionality of the created program code is demonstrated using two hypothetical examples. The program was created using the JavaScript programming language. It accepts as input parameters the maximum daily consumption and the percentage values for each of the time intervals (hours) of consumption. The paper also includes instructions that provide steps for starting a JavaScript program on the Windows operating system.