This article presents the most popular methods of sewage sludge management and associated unit operations and processes referring to them. The most popular methods are: Reclamation and adaptation of ...lands to specific needs; plant cultivation not intended for consumption or for production of food; usage in agriculture; usage in building; recovery of phosphorus, rare earth metals or fats and usage in industry; producing combustible pellets, granulates or other usable materials such as absorbents; and storage on territory of treatment plant and landfills. Processing connected with stabilization leads to generation of materials which might be contaminated with variety of organic compounds. Since this type of management generally assumes introduction of processed sludge to the ground, it can cause soil contamination with unknown compounds of organic origin. However, thermal processing of raw sewage sludge essentially excludes such possibility. Majority of organic matter is transformed into simple, mineralized form. In this case the most problematic issue is sewage sludge ash contamination with heavy metals. Although, determination of heavy metals in ashes is much simpler than determination of organic compounds. Chemical analysis can be very useful to asses environmental safety of processed and managed sewage sludge. That is why there is a significant quantity of used analytical techniques which are likely to support the processes of designing and implementing new economically and environmentally reasonable ways of re-using sewage sludge. Further, the process of technological utilization of sewage sludge conducted in Wastewater Treatment Plant “Wschód” in Gdańsk is described. Recently technological line was upgraded. Now excessive sewage sludge is anaerobic digested with biogas recovery. Fermentation residues are incinerated in fluidized bed furnace. Ashes are cemented and land filled. Gdańska Infrastruktura Wodociągowo-Kanalizacyjna, which is owner of the treatment plant “Wschód“ is planning development strategy for the implementation of a pro-ecological management method connected with production of light construction materials and phosphorus recovery. Management of thermal treated sewage sludge is simpler and cheaper than non-thermal management, especially in case of large amounts of treated sewage sludge like in Wastewater Treatment Plant “Wschód”. Management in smaller installations of treatment plants collecting sewage sludge from less industrialized agglomerations is also less complicated. Sewage sludge management process should be developed separately for each treatment plant. Only then all management methods will be ecologically and economically justified.
•Main sewage sludge management methods are described.•Analytical methods used in sewage sludge management process are described.•Law related to the sewage sludge management are given.
The article presents the results of the analysis, which was carried out in 2015-2017 on the example of autothermal installation of thermophilic sludge stabilization (ATAD) in a sewage treatment plant ...in Giżycko. The installation was created in 2003 as the first of its kind and works until now. The purpose of the conducted research was to assess the suitability of the analyzed technological parameters as tools that can be used by operators to determine the real possibilities of changing the operating conditions of the installation or to develop an optimization strategy to reduce the energy demand. The dry mass content and organic dry mass content was used as the assessment indicators. In the analysed period, sludge from the process contained from 47.47% to 60.80% of organic matter in the dry mass of the sludge. The organic dry matter decrease as due to the process was also calculated, and it ranged from 26.4% to 48.7%. The amount of sludge undergoing the process and the amount of electricity consumption were also analysed. On this basis, the energy consumption indicators in the ATAD process were calculated.
The article presents research on the assessment of electrolytic conductivity changes of sludge during the process of its autothermal thermophilic aerobic digestion (ATAD), which takes place in a ...two-stage installation system, operating in a municipal sewage-treatment plant. In the years 2012-2014 sludge was studied and the results were analyzed. Thickened sludge in the intermediate tank, which was then directed to installation reactors, was examined. Conductivity was measured in each tank. In this manner collected results made it possible to follow the changes of this index at consecutive stages of the system. The results were statistically analyzed and it was determined to what degree, as a result of an objective process, the values of processed sludge conductivity would change. The conclusions from the carried-out studies and from own experiments are also presented.
MnOx/sewage sludge-derived activated carbon (MnOx/SAC) was prepared as catalysts to improve the performance of aqueous oxalic acid degradation by ozonation. The results indicated that MnOx/SAC had ...excellent catalytic activity in mineralization of oxalic acid during heterogeneous catalytic ozonation process. MnOx/SAC with a manganese load of 30% exhibited the strongest catalytic activity under the condition of solution pH3.5, which enhanced the oxalic acid removal from 10.3% to 92.2% in 60min compared with that treated by ozone alone. Increase of catalyst dosage and aqueous ozone concentration was advantageous for oxalic acid removal from water. On the basis of catalyst characterization analysis and the observation of inhibitory effect induced by higher pH, less catalyst dosage as well as the presence of hydroxyl radical scavenger, it was deduced that the reaction mechanism involved both hydroxyl radicals attack and surface reactions.
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•Sewage sludge was converted into catalyst (MnOx/SAC) in ozonation and characterized.•The effectiveness of mineralization of oxalic acid by catalytic ozonation with MnOx/SAC was proved under various conditions.•The enhancement of catalytic activity was attributed to surface reactions and hydroxyl radical generation.•The removal rate of oxalic acid had a positive relationship with the surface hydroxyl group in the catalyst.
With the quick increase in industrialization and urbanization, a mass of sludge has been produced on the account of increased wastewater treatment facilities. Sewage sludge (SS) management has become ...one of the most crucial environmental problems because of the existence of various pollutants. However, SS is a carbon-rich material, which has favored novel technologies for biochar production, which can be utilized for dissimilar applications. This review systematically analyzes and summarizes the pretreatment, modification, and especially application of sewage sludge-derived biochar (SSBC), based on published literature. The comparative assessment of pretreatment technology such as pyrolysis, hydrothermal carbonization, combustion, deashing, and co-feeding is presented to appraise their appropriateness for SS resource availability and the production of SSBC. In addition, the authors summarize and analyze the current modification methods and divide them into two categories: physical properties and surface chemical modifications. The applications of SSBC as absorbent, catalyst and catalyst support, electrode materials, gas storage, soil amendment, and sold biofuel are reviewed in detail. Furthermore, the discussion about the existing problems and the direction of future efforts are presented at the end of each section to envisage SS as a promising opportunity for resources rather than a nuisance.
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•Pretreatment technologies of sewage sludge-derived biochar (SSBC) were reviewed.•A comparison study of well-known pretreatment technologies was presented.•Modification method and activation mechanism of SSBC were summarized and analyzed.•Various applications of SSBC were systematically reviewed and analyzed.•More attention should be paid to the potentially harmful influence of SSBC.
It is estimated that literally billions of residents in urban and peri-urban areas of Africa, Asia, and Latin America are served by onsite sanitation systems (e.g. various types of latrines and ...septic tanks). Until recently, the management of faecal sludge from these onsite systems has been grossly neglected, partially as a result of them being considered temporary solutions until sewer-based systems could be implemented. However, the perception of onsite or decentralized sanitation technologies for urban areas is gradually changing, and is increasingly being considered as long-term, sustainable options in urban areas, especially in low- and middle-income countries that lack sewer infrastructures.
This is the first book dedicated to faecal sludge management. It compiles the current state of knowledge of the rapidly evolving field of faecal sludge management, and presents an integrated approach that includes technology, management, and planning based on Sandecs 20 years of experience in the field. Faecal Sludge Management: Systems Approach for Implementation and Operation addresses the organization of the entire faecal sludge management service chain, from the collection and transport of sludge, and the current state of knowledge of treatment options, to the final end use or disposal of treated sludge. The book also presents important factors to consider when evaluating and upscaling new treatment technology options. The book is designed for undergraduate and graduate students, and engineers and practitioners in the field who have some basic knowledge of environmental and/or wastewater engineering.
Authors: Linda Strande,Eawag, Switzerland, Mariska Ronteltap, UNESCO-IHE Institute for Water Education, Delft, The Netherlands and Damir Brdjanovic, UNESCO-IHE Institute for Water Education, Delft, The Netherlands
Agricultural sewage sludge utilization becomes less important in Germany. In 2017, new fertilizer and waste laws caused the agricultural sewage sludge utilization to collapse by more than a quarter. ...From 2029, German wastewater treatment plants (WWTPs) must recover phosphorus (P) from sewage sludge if it contains more than 2 wt % P. Agricultural utilization will be prohibited for large WWTPs >100,000 population equivalents (pe) from 2029 and > 50,000 pe from 2032. In Germany, each federal state must annually report amounts and quality of agriculturally utilized sewage sludge which was 16% of the total disposal in 2019. The reports of 10 states were evaluated for 2016 and 2017 representing approx. 60% of the total agriculturally used sludge volume. In 2016, 60% of the WWTPs’ sludges exceeded the recovery limit of 2 wt % P which is 70% of the amount of sludge and 85% of the phosphorus load. Other nutrients are not affected by the recovery obligation. However, many P recovery processes recover other nutrients, too. Considering three different scenarios for future German sewage sludge disposal shows that 70–77% of the P load in sewage sludge will probably be recovered in the future. At the same time, this applies for about 0–16% nitrogen, 36–52% of calcium, 31–53% of potassium, and 40–52% of magnesium. However, these recovered nutrients loads can substitute only 1% or less of the commercial fertilizer demand except from phosphorus which is up to 43% of the demand.
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•From 2029, phosphorus (P) recovery is obligatory for sludges with more than 2% P.•P contents in sewage sludge rise with the wastewater treatment plant (WWTP) size.•According to evaluated data, 40% of the German WWTPs fall below this 2% P limit.•Future German P recovery (>70%) could substitute 44% of the mineral fertilizers.•Lost nutrient potentials apart from P are low (<1%) compared to the demand.
•The high output of MSS highlights the need for alternative routes of valorization.•Evaluation of 3 sludge-to-energy valorisation methods through SWOT analysis.•Pyrolysis is an energy and material ...recovery process resulting to ‘zero waste’.•Identification of challenges and barriers for MSS pyrolysis in Greece was investigated.•Adopters of pyrolysis systems face the challenge of finding new product markets.
For a sustainable municipal sewage sludge management, not only the available technology, but also other parameters, such as policy regulations and socio-economic issues should be taken in account. In this study, the current status of both European and Greek Legislation on waste management, with a special insight in municipal sewage sludge, is presented. A SWOT analysis was further developed for comparison of pyrolysis with incineration and gasification and results are presented. Pyrolysis seems to be the optimal thermochemical treatment option compared to incineration and gasification. Sewage sludge pyrolysis is favorable for energy savings, material recovery and high added materials production, providing a ‘zero waste’ solution. Finally, identification of challenges and barriers for sewage sludge pyrolysis deployment in Greece was investigated.
•Drivers behind sewage sludge incineration clearly demonstrated.•Technical detail on the incineration process and ash characteristics provided.•The 1st ever multi-disciplinary review of ISSA re-use ...is presented.•The optimum ISSA re-use routes are identified.•The first time acid insoluble ISSA residue has been considered as a resource.
The drivers for increasing incineration of sewage sludge and the characteristics of the resulting incinerated sewage sludge ash (ISSA) are reviewed. It is estimated that approximately 1.7 milliontonnes of ISSA are produced annually world-wide and is likely to increase in the future. Although most ISSA is currently landfilled, various options have been investigated that allow recycling and beneficial resource recovery. These include the use of ISSA as a substitute for clay in sintered bricks, tiles and pavers, and as a raw material for the manufacture of lightweight aggregate. ISSA has also been used to form high density glass–ceramics. Significant research has investigated the potential use of ISSA in blended cements for use in mortars and concrete, and as a raw material for the production of Portland cement. However, all these applications represent a loss of the valuable phosphate content in ISSA, which is typically comparable to that of a low grade phosphate ore. ISSA has significant potential to be used as a secondary source of phosphate for the production of fertilisers and phosphoric acid. Resource efficient approaches to recycling will increasingly require phosphate recovery from ISSA, with the remaining residual fraction also considered a useful material, and therefore further research is required in this area.
Red mud was evaluated as an alternative skeleton builder combined with Fenton's reagent in sewage sludge conditioning. The results show that red mud combined with Fenton's reagent showed good ...conditioning capability with the pH of the filtrate close to neutrality, indicating that red mud acted as a neutralizer as well as a skeleton builder when jointly used with Fenton's reagent. Through response surface methodology (RSM), the optimal dosages of Fe2+, H2O2 and red mud were proposed as 31.9, 33.7 and 275.1 mg/g DS (dry solids), respectively. The mechanism of the composite conditioner could be illuminated as follows: (1) extracellular polymeric substances (EPS), including loosely bound EPS and tightly bound EPS, were degraded into dissolved organics, e.g., proteins and polysaccharides; (2) bound water was released and converted into free water due to the degradation of EPS; and (3) morphology of the conditioned sludge exhibited a porous structure in contrast with the compact structure of raw sludge, and the addition of red mud formed new mineral phases and a rigid lattice structure in sludge, allowing the outflow of free water. Thus, sludge dewatering performance was effectively improved. The economic assessment for a wastewater treatment plant of 370,000 equivalent inhabitants confirms that using red mud conditioning, combined with Fenton's reagent, leads to a saving of approximately 411,000 USD/y or 50.8 USD/t DS comparing with using lime and ordinary Portland cement combined with Fenton's reagent, and approximately 612,000 USD/y or 75.5 USD/t DS comparing with the traditional treatment.
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•The feasibility of using red mud as a novel skeleton builder was demonstrated.•The degradations of LB-EPS and TB-EPS into dissolved organics were determined.•The conversion of bound water into free water was illustrated by DSC.•New mineral phases and a rigid porous structure were identified by XRD and SEM.•The economic benefits were confirmed for a WWTP of 370,000 IE.
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