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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. 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·PO2 /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]

In order to enhance the effects of concentration and dewatering, sludge is prepared (treated) before. The aim of conditioning sludge before dewatering is to reduce, not only its resistance but also its compressibility. The article presents the analysis of the impact of combined methods of conditioning (ultrasonic field, inorganic coagulant, cationic polyelectrolyte) on the changes in final hydration of sewage sludge in the process of pressure filtration. The study involved sewage sludge after the process of methane fermentation and stabilization in open digesters. The aim of the work was to show that by using the energy of ultrasound and chemical substances, it is possible to change the properties of sewage sludge through changing the dimensions and the capacity of particle packing, thus improving the effectiveness of dewatering. Digested sludge is hard to dewater, which is proved by its capillary suction time (CST), amounting to 1,859 s. The lowest CST value (29.3 s) and final hydration (65%) were obtained for sludge sonicated for 60 s (amplitude 30.5 µm) prepared with PIX 113 (coagulant) in the dose of 1.0 mg/gd.o.m. (d.o.m. - dry organic mass) and Zetag 8180 (polyelectrolyte) in the dose of 7.0 mg/gd.o.m. The application of an ultrasonic wave and chemicals to modify sewage sludge caused the reduction in the value of final hydration and thus led to better results of sludge dewatering in the process of pressure filtration. In addition, the combined use of ultrasound, PIX 113 and Zetag 8180 reduced the content of suspended solids, phosphorus and ammonium nitrogen in sludge liquids. [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]

To increase the dewatering effect, sewage sludge should be properly prepared before dewatering. Sludge conditioning is a process whereby sludge solids are treated with chemicals or various other means to improve dewatering characteristics of the sludge by reducing the specific resistance and compressibility of the sludge. The aim of the research was to determine the possibility of increasing the efficiency of sewage sludge dewatering by applying chemical agents and ultrasonic field. Some parameters, such as suspension, chemical oxygen demand (COD), phosphorus and ammonium nitrogen content in sludge supernatant, were also analysed. Digested sludge belonged to the group of hardly dewatered sludge, its capillary suction time (CST) was of high value (2639 s). The lowest CST value (88.5 s) was obtained for the unsonicated sludge prepared only with PIX 113 at a dose of 7.0 mg/g d.m. Both the dose and the type of chemicals used, as well as the time of sonication, had an impact on the changes occurring in sludge properties. The increase in mechanical dewatering efficiency was obtained by using a combination of methods applied for sludge preparation, where the sonication of sludge was used at the preliminary stage and followed by dosing chemical substances. This resulted in the reduction of sludge final hydration and changes of other parameters. In addition, combined action of PIX 113 and Zetag 8180 allowed to reduce the content of suspended solids and COD in sludge supernatant. [ABSTRACT FROM AUTHOR]

The article presents the results of sulfur and nitrogen conversion to flue gas components during the oxy-combustion of municipal sewage sludge. In Poland, some dynamic changes in the implementation of thermal treatment methods in sewage sludge management have been observed over recent years. A few new installations have been commissioned with a fluidized bed technology under air-firing conditions. Until 30th December 2012, there were in Poland, 11 municipal sewage sludge incineration plants that had jointly a total capacity amounting to 160,000 Mg/y. Since the oxy-combustion technology has been researched widely mainly in coal combustion, the experiments carried out at 0.1 MWthCFB combustor have focused on sewage sludge combustion and sulfur, nitrogen conversion to flue gas components in the conditions of increased oxygen concentration and different process temperatures. The oxygen concentration in a feed gas was increased from 21 to 35% per volume. An increase in sulfur and nitrogen conversion ratios was found under the oxy-combustion conditions. [ABSTRACT FROM PUBLISHER]

The article presents the results of research on the impact of inorganic coagulants and polyelectrolytes and their common action on non-prepared and sonicated digested sludge. Sonication of sludge samples was carried out under static conditions for 60, 120, and 180 s. An ultrasonic wave off = 20 kHz and two different amplitudes ofA = 15.25 and 30.5 μm were used in tests. The coagulant PIX123 and the polyelectrolyte Zetag 8160 were used for conditioning. On the basis of CST test, doses of chemical reagents were chosen for conditioning. The results indicated the effect of the PIX123 and Zetag 8160 application on non-sonicated and sonicated sludge. The lowest CST values were achieved, while the combination of coagulant in a fixed dose of 1.0 mg/g and polyelectrolyte was used. This effect was observed for non-sonicated sludge as well as for sonicated sludge. The higher dose of chemical reagent used for non-sonicated sludge, the lower the final hydration was achieved. For non-sonicated sludge, better results were obtained when the Zetag 8160 was used. For sonicated sludge, better results were achieved when PIX123 was used. The effect of the final hydration reduction for sonicated sludge and prepared with Zetag 8160 was not satisfactory. The application of the coagulant and the polyelectrolyte combination does not allow achieving lower final hydration of sludge in comparison with only PIX 123. However, it was possible to achieve higher suspension and COD reduction. [ABSTRACT FROM PUBLISHER]

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]

The paper presents the impact of different methods of sewage sludge conditioning on the improvement of sludge dewatering during pressure filtration processes. The following conditioning methods were tested for sludge preparation: sonication, addition of organic and inorganic chemicals (Zetag 8180, PIX 113 and the combined action of both substances). The research covered: physical and chemical analysis of sewage sludge, measurement of capillary suction time as an indicator of sludge dewaterability, some technical parameters of sludge pressure filtration process and the analysis of filtrate to assess the degree of contamination. The results of the research showed that the final water content of the prepared sludge decreased, while the specific filtration resistance increased. Among the tested methods the best results of sludge dewatering effects were obtained for sonicated sludge and its preparation with inorganic coagulant PIX 113. The combined effect of sonication with the addition of chemicals Zetag 8180 and PIX113 to sludge allowed for the reduction of organic substances, ammonium nitrogen and phosphates in filtrate after sludge dewatering. [ABSTRACT FROM AUTHOR]

The paper presents the research on the possible use of inorganic coagulants and polyelectrolytes for conditioning of sonicated and non-sonicated sewage sludges and the impact of conditioning process on the sludge rheological parameters and dewatering process. Dewatering of sludge with a high share of organic matter or sludge with a high percentage of fine fractions and colloidal suspensions causes clogging of the filter, and an increase in filtration resistance does not bring good technological and economic effects. To improve the degree of dewatering of such sonicated and non-sonicated sludges, coagulants and polyelectrolytes and their mixture in appropriate proportions and conditions could be used. The usage of both substances: PIX and polyelectrolyte helped to achieve a cleaner filtrate in comparison with when only polyelectrolyte is used. The rheological parameters of sludge, its structure as well as processes parameters, such as vacuum filtration and pressure filtration were determined during tests. The results show that during application in the conditioning of sonicated sludge, both chemical substances (inorganic coagulant and polyelectrolyte) resulted in a significant improvement of parameters used in order to determine the susceptibility to sludge dewatering. [ABSTRACT FROM AUTHOR]