Due to the key role of the biological decomposition process of organic compounds in wastewater treatment, a very important thing is appropriate aeration of activated sludge, because microorganisms have to be supplied with an appropriate amount of oxygen. Aeration is one of the most energy-consuming processes in the conventional activated sludge systems of wastewater treatment technology (may consume from 50% to 90% of electricity used by a plant), which makes it the most cost-generating process incurred by treatment plants. The paper presents the construction of aeration systems, their classification as well as parameters and factors that significantly affect the aeration process e.g., oxygen transfer efficiency, diffuser fouling, methods of dealing with diffuser fouling, diffuser selection. Additionally, there are briefly presented “smart control” systems in wastewater treatment and effect of application control strategy based on Supervisory Control and Data Acquisition system connected with the decrease in the energy consumption for aeration of bioreactors with activated sludge. It is noted that before the process is optimized, the system should be equipped with suitable metering devices. Only when relevant data is available, the improvements can be carried out. However, it’s important, that the operator should regularly maintain good condition and high efficiency of diffusers.

Novel technologies such as partial nitritation (PN) and partial denitritation (PDN) could be combined with the anammox-based process in order to alleviate energy input. The former combination, also noted as deammonification, has been intensively studied in a frame of lab and full-scale wastewater treatment in order to optimize operational costs and process efficiency. For the deammonification process, key functional microbes include ammonia-oxidizing bacteria (AOB) and anaerobic ammonia oxidation bacteria (AnAOB), which coexisting and interact with heterotrophs and nitrite oxidizing bacteria (NOB). The aim of the presented review was to summarize current knowledge about deammonification process principles, related to microbial interactions responsible for the process maintenance under varying operational conditions. Particular attention was paid to the factors influencing the targeted selection of AOB/AnAOB over the NOB and application of the mathematical modeling as a powerful tool enabling accelerated process optimization and characterization. Another reviewed aspect was the potential energetic and resources savings connected with deammonification application in relation to the technologies based on the conventional nitrification/denitrification processes.

The production of sodium hypochlorite (NaOCl) from salty wastewater using an electrochemical cell has several advantages over other methods that often require hazardous chemicals and generate toxic waste, being more sustainable and environmentally friendly. However, the process of producing sodium hypochlorite using an electrochemical cell requires careful control of the operating conditions, such as the current density, flow rate, inert electrode spacing, and electrolyte concentration, to optimize the conversion efficiency and prevent electrode fouling and degradation. In this study, NaOCl was produced via a bench-scale electrochemical cell using a flowing porous graphite electrode in a continuous flow system from salty wastewater collected from the Suez Canal in Egypt. The aim of the investigation was to examine the factors that affect the concentration of NaOCl and energy consumption, such as anodic current density, salinity, inert electrode spacing, and influent feed flow rate. A lab-scale reactor with two electrodes was used to conduct the experiments. The highest NaOCl yield of 20.6% was achieved with a graphite electrode, which had high current efficiency and rigidity at a flow rate of 4.5 mL/min, a current density of 3.183 mA/cm², an electrode space of 0.5 cm, salinity of 40,000 ppm, and a pH of 6.4. The power consumption under these conditions was 0.0137 kwh. Additionally, a statistical and least square multivariate regression technique was employed to establish a correlation for predicting the % NaOCl production. The obtained correlation had an R² value of 98.4%. Overall, this investigation provides valuable insights into the production of NaOCl using a continuous flow system from salty wastewater, which could have potential for industrial applications in various sectors such as textiles, detergents, paper, and pulp.

The paper presented the methodology for the construction of a soft sensor used for activated sludge bulking identification. Devising such solutions fits within the current trends and development of a smart system and infrastructure within smart cities. In order to optimize the selection of the data-mining method depending on the data collected within a wastewater treatment plant (WWTP), a number of methods were considered, including: artificial neural networks, support vector machines, random forests, boosted trees, and logistic regression. The analysis conducted sought the combinations of independent variables for which the devised soft sensor is characterized with high accuracy and at a relatively low cost of determination. With the measurement results pertaining to the quantity and quality of wastewater as well as the temperature in the activated sludge chambers, a good fit can be achieved with the boosted trees method. In order to simplify the selection of an optimal method for the identification of activated sludge bulking depending on the model requirements and the data collected within the WWTP, an original system of weight estimation was proposed, enabling a reduction in the number of independent variables in a model—quantity and quality of wastewater, operational parameters, and the cost of conducting measurements.

Composite materials have become synonymous with modernity, desired in nearly every aspect of our daily lives, from simple everyday objects to sanitary facilities, pipelines, the construction of modern sewer networks, their renovation, water supply, and storage reservoirs, to complex structures—automotive, planes, and space science. Composites have seen a considerable rise in attention owing to their characteristics, durability, strength, reduced energy usage during the manufacturing process, and decreased transportation costs. Composite materials consistently outperform steel, cast iron, and concrete in terms of CO₂ emissions. Additionally, these materials have a long service life of about 150 years or more and are corrosion-resistant. Today, continued sustainable development is contingent upon access to safe drinking water and the availability of its resources and modes of conveyance. As a result, composite pipes have considerable potential due to their very low flow rate, which directly affects the prices of drinking water pumping and irrigation systems. However, there are also certain disadvantages associated with fibre-reinforced composites, such as easy surface damage, low heat resistance (up to 220 °C), long product forming time, and high cost of the material. Additionally, the product’s initial high durability and extended life cycle, coupled with high abrasion resistance, anisotropic strength, and stiffness in the final phase, prove to be unfavourable since composite material cannot be rapidly reintroduced into the manufacturing cycle. However, its disposal requires a negligible amount of energy. The article discusses the various composite materials available, their applications, and the potential for further developing their manufacturing technology toward nanocomposites and composites of natural origin that are readily biodegradable at the end of their service life; dubbed “green composites”. The study’s findings are unequivocal: this class of composite materials warrants further investigation in the future since they align perfectly with the concept of sustainable economic growth and Green Deal implementation.

The efficiency of denitrification and enhanced biological phosphorus removal in biological nutrient removal activated sludge systems is strongly dependent on the availability of appropriate carbon sources. Due to high costs of commercial compounds (such as methanol, ethanol, acetic acid, etc.) and acclimation periods (usually) required, the effective use of internal substrates is preferred. The aim of this study was to determine the effects of slowly biodegradable compounds (particulate and colloidal), as internal carbon sources, on denitrification, phosphate release/uptake and oxygen utilization for a full-scale process mixed liquor from two large wastewater treatment plants located in northern Poland. Since it is difficult to distinguish the effect of slowly biodegradable substrate in a direct way, a novel procedure was developed and implemented. Four types of one- and two-phase laboratory batch experiments were carried out in two parallel reactors with the settled wastewater without pre-treatment (reactor 1) and pre-treated with coagulation–flocculation (reactor 2). The removal of colloidal and particulate fractions resulted in the reduced process rates (except for phosphate release). The average reductions ranged from 13 % for the oxygen utilization rate during the second phase of a two-phase experiment (anaerobic/aerobic), up to 35 % for the nitrate utilization rate (NUR) during the second phase of a conventional NUR measurement.