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Sludge management account for high economic costs and energy consumption in wastewater treatment. Accurate forecasting of sewage sludge generation thus can be important for the planning, operation and optimization of processes at wastewater treatment plant (WWTP). In this study data from a municipal treatment plant with a capacity of 88 thousand cubic meters of sewage per day located in south part of Poland were used to find a good forecasting model for sludge amount prediction. Among models an autoregressive integrated moving average (ARIMA) is one of the popular linear models in time series forecasting. Since the ARIMA model cannot capture the non-linear structure of the data research activities in forecasting suggest using neural networks. Long-short term memory (LSTM) recurrent neural network proved its usability in time series forecasting. Looking at the curve representing data of sludge amount generated in the previous years at WWTP the linear and non-linear patterns could be distinguished. To address these issue a hybrid methodology that combines advantage of ARIMA and LSTM was proposed and used for forecasting purpose. Experimental results showed that the combined model can be an effective way to improve the forecasting accuracy of sludge amount generated at this WWTP. [ABSTRACT FROM AUTHOR]

A new approach to the problem of sludge liquids in wastewater treatment plants involves the use of technologies designed not only for increased removal of nitrogen and phosphorus from leachate, but primarily for the recovery of nutrients. Due to the high content of nitrogen and phosphorus in sludge liquids separated from digested sludge, they were found to be a potential source for the recovery of biogenic compounds. The selection of appropriate chemical and physical agents for conditioning of digested sludge is one of the factors that have a significant impact on the quality of sludge liquids. The article presents the effect of conditioning methods (ultrasonic field, coagulant PIX 123, polyelectrolyte Zetag 8160) on the content of organic and nutrient compounds in sludge liquids. The raw sludge liquids were characterized by very high phosphate concentrations: 122.4 mg·PO4 3–/L, ammonium nitrogen: 1,718 mg·N–NH4 + /L) and organic compounds determined as chemical oxygen demand (COD) 2,240 mg·O2 /L. The aim of the study was to determine the effect of selected methods of conditioning digested sewage sludge on the quality of sludge liquids obtained after the sludge dewatering process. The scope of the study included measurement of pH, phosphate, ammonium nitrogen and COD concentration in sludge liquids. The highest amount of phosphate was recorded in sludge liquids separated from sonicated sludge (A = 45.75 µm, t = 60 s). It was 355.5 mg·PO4 –3/L (an increase of 190.4% was noted compared to phosphate concentration in raw liquids). Keywords: Sludge liquids; Sludge conditioning; Biogenic compounds; Nitrogen; Phosphorus [ABSTRACT FROM AUTHOR]

Adopting the idea of the circular economy, European Commission on 4 March 2019, delivered 54 actions in a form of a comprehensive report on the implementation of the Circular Economy Action Plan. These actions would lead to resource-efficient and environmentally friendly outcomes. In general, biological materials should be returned to the natural metabolic cycles after necessary pre-treatment while waste that cannot be prevented or recycled is to be used for energy recovery. Sewage sludge is a large-tonnage waste produced at wastewater treatment plants (WWTPs). Its utilization causes some problems. Among many different ways of sludge utilization, its thermal treatment has to be taken into account. During thermal treatment some hazardous substances in sewage sludge can be destroyed or removed, energy can be recovered and some nutrients can be obtained from ash or other by-products. According to the information from the Polish Central Statistical Office (GUS), in 2017 in Poland, 584.5 thousand tonnes of sewage sludge dry mass was produced at municipal WWTPs. More than 100 thousand tonnes of was subject to thermal processing. The paper presents the situation within Polish wastewater treatment plants in which thermal treatment has been activated in terms of preparation for the implementation of the rules resulting from the Circular Economy Action Plan. [ABSTRACT FROM AUTHOR]

Reject water separated from digested sludge may be a potential source of nutrients due to its high content. However, most often, reject water after sludge dewatering is directed to sewage lines at wastewater treatment plants, negatively affecting their operation, especially in the biological part. The activities related to sludge conditioning before dewatering have a direct impact on the quality of the reject water. The reject water of raw digested sludge is characterized by very high concentrations of ammonium nitrogen, at 1718 mgN-NH4+/dm3; phosphates, at 122.4 mgPO43−/dm3; and chemical oxygen demand (COD), at 2240 mgO2/dm3. The objective of the research was to determine the impact of selected sludge conditioning methods on the quality of reject water obtained after sludge dewatering. The following parameters were analyzed in the reject water: the chemical oxygen demand (COD), phosphates, ammonium nitrogen, and total suspended solids (TSS). It has been observed that the sludge sonification process increases the content of impurities (COD, phosphates) in reject water with an increase in the amplitude of the ultrasonic field. On the other hand, the chemical reagents cause a decrease in the concentration of the pollutants with an increase of the chemical dose. It has been found that the inorganic coagulant PIX 113 gives much better results regarding the reduction of contamination than the polyelectrolyte Zetag 8180. [ABSTRACT FROM AUTHOR]