Introduction : The spreading of bacterial antibiotic resistance among clinical strains of pathogenic bacteria has made investigators to search for other active antibacterial agents which could provide a valuable complement to the existing therapies. Aim: To determine the antibacterial...

This article presents the potential of heat recovery from wastewater with an example of a wastewater treatment plant (WWTP) in Mokrawica, which is located in the West Pomeranian region of Poland. A thorough literature review discusses the relevance of the topic and shows examples of heat recovery conducted with heat pumps. Raw and treated wastewater are mostly used as heat sources, with the latter achieving higher thermal capacities. Heat recovery from a biological treatment process is rarely implemented and requires more detailed studies on this subject. The proposed methodology for estimating possible heat recovered from wastewater, requiring heating and cooling capacities, as well as the coefficient of performance (COP) of a heat pump, is based on only three parameters: wastewater volumetric flow, wastewater temperature, and the required temperature for heating or air-conditioning. The heat recovery potential was determined for different parts of WWTP processes, i.e., the sand box, aeration chamber, secondary sedimentation tank, and treated sewage disposal. The average values of 309–451 kW and a minimum of 58–68 kW in winter were determined. The results also indicate that, depending on the location of the heat recovery, it is possible to obtain from wastewater between 57.9 kW and 93.8 kW of heat or transfer to wastewater from 185.9 to 228.2 kW. To improve biological treatment processes in the winter season, wastewater should be preheated with a minimum of 349–356 kW that can be recovered from the treated wastewater. The heat transferred to the wastewater from the air-conditioning system amounts to 138–141 kW. By comparing the required cooling and heating capacities with the available resources, it is possible to fully recover or transfer the heat for central heating, hot water, and air conditioning of the building. Partial preheating of wastewater during the treatment process requires further analysis.

Extraneous water that inflow to the sewage system is basically divided into two streams—accidental water (mainly rainwater) and infiltration water. The aim of the research was to assess the amount of extraneous water inflow to the considered system. Five different quantitative approaches were applied. Three well-known methods were used: the triangle method, the minimum night flow method, and the moving minimum method. The annual balance of water consumption and sewage supply to the wastewater treatment plant were calculated. Also, some analysis of sewage discharge during wet and dry weather was carried out. The study covered data from 6 years from 2014 to 2019. It was established that the main source of extraneous water was infiltration, because three methods which concern both streams (triangle method, minimum night flow, variability in wet and dry weather) confirm the conclusion. Merely the moving minimum method results differ from the others. In this investigation, accidental water (basically rainwater inflow) poses a significantly less share in the total volume of sewage compared to infiltration water. The total amount of extraneous water was estimated as in the range from 38 to 53% of annual sewage supply to wastewater treatment plant, depending on the year. Share of infiltration and accidental water is changing in different methods. Share of infiltration was in a range between 18 and 68%, depending on the year and the method used. Share of accidental water was in a range between 7 and 22%.

In line with the trend of using waste raw materials in the technology of building materials, experimental studies of cement mortars containing various amounts of fine-grained waste aggregate were carried out. The waste aggregate was based on an incinerated municipal sewage sludge which was mechanically crushed to an appropriate grading. Chemical and physical properties of the waste aggregate are presented. Mortars with varying amounts of waste aggregate as a replacement for natural sand were prepared. Study determines compressive strength and flexural strength up to 56 days. Properties such as capillary action, air content and thermal conductivity were determined. The results of the tests has shown that the incinerated waste sludge can be used as a partial or total replacement for natural aggregate. In mortars with waste aggregate, a favorable relation between flexural and compressive strengths was observed, which translates into increased strength of the interfacial transition zone. A significant increase in water absorption was observed for mortars containing high amounts of waste aggregate, which is directly related to its porous structure. Conducted studied prove that the aggregate obtained from incineration of the municipal sewage sludge can a feasible alternative for natural aggregates in production of masonry and rendering mortars for construction purposes.

The aim of the study was to determine the physical and chemical properties of sewage sludge from municipal wastewater treatment plants “Pomorzany” and “Zdroje” located in Szczecin, Poland. The paper presents outcomes of SEM observation of dried and stabilized sewage sludge. The research...