Sludge Reduction Technologies Research Articles

Sludge lysis by thermophilic bacteria community enhances nutrient removal, sludge reduction, and modulates microbial community in anaerobic-anoxic-oxic process

Excess sludge generated during the biological treatment of wastewater is returned to the biochemical tank after being lysed, which is considered to be a feasible strategy for reducing sludge. In this study, an in-situ sludge reduction technology combining sludge lysed based on thermophilic bacterial community (LTBC) and anaerobic-anoxic-oxic (AAO) process (i.e., LTBC-AAO process) was proposed for the first time and the sludge reduction efficiency of the LTBC-AAO process was evaluated. In LTBC reactor, the average removal efficiency of volatile suspended solids of sludge was 52.1 ± 3.2 %. Thermophilic bacteria involved in sludge lysis included Thermus, Fervidobacterium and Caldanaerobacter with relative abundances of 51.5 %, 20.3 % and 8.72 %, respectively. The excess sludge of LTBC-AAO was reduced by 64.7 % compared with that of conventional AAO. The COD removal efficiencies of LTBC-AAO and AAO were 93.4 ± 1.8 % and 93.1 ± 2.1 %, respectively, and there was no significant difference. The TN removal efficiency of LTBC-AAO was 65.7 ± 4.2 %, which was 10 % higher than that of AAO (55.7 ± 3.2 %). Furthermore, 65.7 % substrate in lysed sludge supernatant was readily biodegradable, and the denitrification rate of these substrates as carbon source was 6.33 mg N/g VSS-h. Microbial community structure analysis revealed increased microbial diversity of activated sludge due to lysed sludge reflux, with enrichment of denitrification-related species Delftia and Acinetobacter in LTBC-AAO contributing to the improvement in nitrogen removal efficiency. These findings suggest that the LTBC-AAO process is a promising technology for sludge reduction and nutrient removal in municipal wastewater treatment plants.

Full-Scale Sewage Sludge Reduction Technologies: A Review with a Focus on Energy Consumption

In recent years, increasing attention has been paid to the problem of sewage sludge management and the relevant energy consumption, which represent the main cost items in wastewater treatment plants. Therefore, implementation of technologies that can reduce sludge production and ensure a positive impact on the energy of the entire sewage treatment plant has gained considerable importance in the scientific and technical community. The objective of this study was thus to screen full-scale sludge reduction technologies integrated into both the water line and the sludge line of a municipal sewage treatment plant with a sustainable impact on the overall balance of the plant. The results showed that, within the water line, ultrasound in the recirculation line of the activated sludge allowed for greater reductions in sludge production than the Cannibal and UTN systems, despite the higher energy consumption. CAMBITM, BioThelysTM, ExelysTM and TurboTec® enabled the greatest reductions in sludge production among the technologies integrated into the sludge line, and although they required a large amount of energy, this was partially offset by energy recovery in terms of additional biogas production.

A comparative life cycle assessment (LCA) analysis of innovative methods employing cutting-edge technology to improve sludge reduction directly in wastewater handling units

Sludge reduction technologies can be used as an alternative plan to dispose of excess sludge in wastewater treatment plants, but the sustainability of these strategies is a challenging task. In this study, the potential environmental implications of innovative technologies based on lab-scale results published in the literature were assessed from the life cycle assessment (LCA) view point. Accordingly, three different scenarios using various sludge reduction mechanisms were selected and analyzed. The scenarios include (1) an integrated oxic-setting-anaerobic and ultrasound process; (2) a sequencing batch reactor (SBR) with an anaerobic side-stream reactor to its return activated sludge line; and (3) the anaerobic-anoxic-oxic system in conjunction with an ozone reactor. LCA was conducted through the CML-IA (baseline 2000) method. A sensitivity analysis was also done in order to determine how changes in the inputs are affecting the overall sustainability of the system. The environmental impact evaluation of three scenarios indicated that the integrated SBR with an anaerobic side-stream reactor was the most efficient and sustainable alternative in environmental terms. Although the upgraded SBR system was not the best alternative in terms of sludge reduction (65 % versus 78 % for Scenario 1 and 70 % for Scenario 3), it showed the highest overall performance and also demonstrated the lowest environmental impact compared to other scenarios. Because the scenarios studied were cutting-edge and provided novel sludge reduction strategies based on lab-scale results published in the literature, a comprehensive economic analysis and scale-up considerations are recommended to effectively assist decision-makers in guiding the development of emerging technologies.

Investigation of sludge dewatering efficiency in the thermal-hydrolysis reactor at various physical operational factors: Performance and fluid dynamic analysis

The sludge produced from various wastewater treatment is waste with various contaminants concentrated. A few decades ago, the sludge was contolled through direct discharge to the water phase, but further treatment is required due to additional environmental pollution issues. However, there are various available carbon-based resources in the sludge. The thermal hydrolysis process can reduce the discharged sludge quantity by improving the dewatering ability. The purpose of this study is to investigate the effect of the physical change factors of the thermal hydrolysis reactor (sludge amount, slope degree, stirring speed and residual oxygen quantity) on the dewatering capacity and solubilization of the thermal hydrolysis process. The highest dewatering capacity and efficiency showed when 7 kg of sludge was injected and slope control mode. The stir speed showed the best results at 150 rpm, but the increase in efficiency slowly up from 100 rpm. In addition, through CFD analysis, the high efficiency reactor slope was optimized. By investigating the performance of the thermal hydrolysis process under various physical conditions and the physical and chemical changes of final products, it is expected that it will be possible to suggest a way to vary the utilization according to the various characteristics of the sludge. Since the optimization of physical changes does not require additional economic cost input, it has the potential to secure the economic feasibility of sludge reduction technology.

Constant-current electro-dewatering of sewage sludge: Effect of anthracite modification on dehydration performance and economic benefit

Electro-dewatering (EDW) is a sludge reduction technology with considerable potential. However, its application is limited by low economic benefit, partially due to energy spent on heating sludge. When the mode of EDW with constant current (C-EDW) is chosen, a substantial amount of energy is wasted to heat the poorly-conductive dry sludge in the late stage of C-EDW. Reducing the sludge electrical resistance can weaken the ohmic heating effect in this process. Therefore, anthracite, a material with good electrical conductivity, was used to modify sewage sludge for C-EDW (constant current at 1 A) in this study, with different dosages (0%−12% mass of dry sludge (DS)) tested and compared. The results show that all anthracite-conditioned groups, with 2%−12% DS of anthracite added to sludge, had lower energy consumption than the blank group when the moisture content was all reduced to 60%. The economic benefit, quantified by an evaluation indicator KsiEDW, was improved by anthracite conditioning comparing all conditioned groups to the blank group. The optimal addition was 6% DS in the study, as the group had the lowest energy consumption (0.128 kWh/kgDS) and KsiEDW (1.71 (kWh/kgDS)·(h/kgDS)). Anthracite also improved the dehydration performance of C-EDW- all conditioned groups had lower final moisture content than the blank group at the same final voltage (60 V), with 51.5% being the lowest (6%DS group).

Preliminary study on in-situ Sludge Reduction technology in the northwest arid areas expressway service area

High-speed service area in the northwest arid areas as the research object, through on-the-spot investigation, sludge and solid waste within the northwest service types, quantity and so on various aspects of information are collected, on the basis of research on sludge reduction technology in situ service areas, to improve the improve the level of expressway service area of the country's solid waste treatment practice experience.

Identifying prokaryotes and eukaryotes disintegrated by a high-pressure jet device for excess activated sludge reduction

Changes in microbial communities are observed during the long-term operation of activated sludge systems employing an excess sludge reduction technology. Short-term changes are also significant to confirm if key microbes are damaged, but they have not been investigated due to the absence of an appropriate method. We report a methodology to identify prokaryotic and eukaryotic species damaged almost instantaneously by a high-pressure jet device (HPJD), a cost-effective sludge reduction technology. 16S rRNA gene amplicon sequencing and microscopic inspection were implemented to identify damaged microorganisms. A sludge injection ratio (R), activated sludge suspension from the top port relative to that of the lateral port of the HPJD, was set at 0, 1, and 3. The DNA eluted by the HPJD treatment at these R-values was successfully retrieved. Nitrifying bacteria were not detected in the eluted DNA at the R-values, indicating that the essential guilds for nitrogen removal can be retained. The dominant phylum was Proteobacteria (47.8 %), followed by Bacteroidetes (18.2 %), Chloroflexi (9.0 %), and Verrucomicrobia (5.8 %) before HPJD treatment. These phyla retained their dominance after HPJD treatment; however, species in the phylum Actinobacteria (6.9–19.9 %) were intensively damaged. A higher degree of sludge destruction by the HPJD increased the species destroyed, but the composition was not changed. The microscopic inspection indicated the HPJD treatment pronouncedly destroyed the eukaryotic metazoa in activated sludge.

Decomplexation removal of Ni(II)-citrate complexes through heterogeneous Fenton-like process using novel CuO-CeO2-CoOx composite nanocatalyst.

A novel CuO-CeO2-CoOx nanocatalyst was prepared for heterogeneous Fenton-like reaction to break the Ni2+-chelate into free Ni2+ in electroless nickel plating wastewater, followed by separation of Ni2+ in an insoluble form. The composite nanocatalysts prepared by co-precipitation method were characterized by XRD, TEM, and XPS, et al. Its catalytic activity as Fenton-like reagent was evaluated by the removal efficiency of Ni(II)-citrate after decomplexation and postprecipitation treatment. Subsequently, the effects of operating parameters on the decomplexation efficiency of the nanocatalysts were investigated including calcination temperature of catalysts, H2O2 concentration, catalyst dosage, initial pH and reaction temperature. Under optimized condition, the Ni(II)-citrate complexes (C0 = 1.0 mM) achieved the complete decomplexation (>99.9%) within 60-min reaction using 0.3 g/L of CuO-CeO2-CoOx calcined at 450 °C and 75 mM of H2O2 at pH 3.0 under 50 °C of reaction. Then, Ni2+ after decomplexation could be completely removed by the subsequent precipitation at pH 11.0. In addition, the life test of CuO-CeO2-CoOx catalyst indicated that, after recycled 10 times, its activity for decomplexation of Ni(II)-citrate decreased no more than 8%. As a result, this new heterogeneous Fenton-like process is promising for decomplexation and purification of electroless nickel plating wastewater as a sludge reduction technology.

Status and Research Progress on Sludge Reduction Technologies

With wastewater treatment capacity increasing rapidly, the issue of excess sludge treatment becomes serious for wastewater treatment plant. Sludge reduction technology becomes one of the effective ways to resolve excess sludge issue at present. Application status of wastewater treatment with sludge reduction were elaborated from uncoupling, cryptic growth and predation of micro faunal three aspects. The principles and characteristics of these techniques were introduced, and their research.

Application of Ultrasound waves for Sludge Dewatering

Because of increase in application of biological processes in wastewater treatment plants the amount of sludge produced by them is increasing rapidly. Therefore finding new sludge reduction technologies in wastewater treatment plants is very important. Nowadays ultrasound waves have an increase rate of application in full scale in wastewater industry. The most important advantages of ultrasound waves are such as: No sludge production, ease of use, increasing the biogas production, contributing to dewatering, no secondary pollution and degradation of complex materials into simpler substances. In this research, different applications of ultrasound waves in wastewater and sludge treatment and improving dewaterabilty of sludge is investigated.DOI: http://dx.doi.org/10.3126/ijls.v9i4.12680

Study on enhanced denitrification using particulate organic matter in membrane bioreactor by mechanism modeling

Particulate organic matter (POM) in wastewater is a potential denitrification carbon source, while the optimal operational mode using denitrification mechanism with POM is still unclear in wastewater treatment plants. In this work, we investigated the denitrification rates (DNRs) in a full-scale membrane bioreactor (MBR) coupled with two-stage pre-anoxic (pre-AN), and then evaluated the POM denitrification efficiency using mechanism modeling. The results indicate that POM related fraction accounted for the majority of the obtained specific DNR of 1.39±0.46mgNg−1 MLVSS h−1 in the second pre-AN without available soluble carbon source. The modeling approaches with calibration and validation procedures estimated a high residual POM concentration of 0.17g COD g−1 MLVSS in the activated sludge, which provided specific DNR of 1.14mgNg−1 MLVSS h−1. High POM retention time in the reactor was the result of high solid retention time used in the MBR. In particular, post-AN of high biomass concentration could provide the highest POM denitrification efficiency in MBR. The MBR process combined with additional sludge reduction technology could further enhance denitrification by POM.

Effect of different sludge reduction methods on sludge reduction rates, performance of activated sludge process and urban planning

AbstractEffect of biological methods (aerobic digestion, anaerobic digestion, and predation by Tubifex tubifex), physical methods (addition of uncoupling agent), and chemical methods (addition of ozone, chlorine) on the efficiency of sludge reduction was compared, so was the effect of different sludge reduction methods on the performance of activated sludge process with respect to the content and nature of organic matters. It was concluded that the best sludge reduction technology was using uncoupling agent with sludge reduction efficiency at 60%, followed by ozone, chlorine, micro-biological, aerobic biological, and anaerobic biological, which was the worst with efficiency at 36%. All of the molecular weight (MW) distribution of supernatant in activated sludge processes was changed to some extent under different sludge reduction methods. The change of the MW distribution would play a certain impact on the biodegradable ability of the organics, thus affecting the efficiency of sludge reduction rate. Final...

Pilot-scale test of an advanced, integrated wastewater treatment process with sludge reduction, inorganic solids separation, phosphorus recovery, and enhanced nutrient removal (SIPER)

Sludge reduction technologies are increasingly important in wastewater treatment, but have some defects. In order to remedy them, a novel, integrated process including sludge reduction, inorganic solids separation, phosphorus recovery, and enhanced nutrient removal was developed. The pilot-scale system was operated steadily at a treatment scale of 10 m(3)/d for 90 days. The results showed excellent nutrient removal, with average removal efficiencies for NH4(+)-N, TN, TP, and COD reaching 98.2 ± 1.34%, 75.5 ± 3.46%, 95.3 ± 1.65%, and 92.7 ± 2.49%, respectively. The ratio of mixed liquor volatile suspended solids (MLVSS) to mixed liquor suspended solids (MLSS) in the system gradually increased, from 0.33 to 0.52. The process effectively prevented the accumulation of inert or inorganic solids in activated sludge. Phosphorus was recovered as a crystalline product with aluminum ion from wastewater. The observed sludge yield Yobs of the system was 0.103 gVSS/g COD, demonstrating that the system's sludge reduction potential is excellent.

ESTIMATING AND MODELLING THE SLUDGE EXCESS DISCHARGE IN WASTEWATER TREATMENT PLANTS IN CHINA

A rapid increase of wastewater treatment plants (WWTPs) has made the disposal of excess sludge from WWTPs a serious problem. In order to enhance the management of sludge, both development of sludge reduction technologies and sludge evaluation system are of great importance. Based on the survey data from 696 plants in China in 2009, an empirical model was developed to simulate the production and discharge of excess sludge, which considered influent, temperature, Chemical Oxygen Demand (COD), Suspended Solids (SS), and Total Nitrogen (TN). Four basic wastewater treatment processes including A2O, Oxidation Ditch, SBR and Traditional Activated Sludge Process were selected for the model verification and related parameters and indicators in the model were calculated. The model was applied in a typical plant with process of Oxidation Ditch in South China. Results indicated that it was available for the simulation of the discharge of excess sludge in actual plant, with exception of data in August and September, mainly due to the relatively lower BOD in these two months. Generally, the empirical model established could be applied in the management of excess sludge disposal in WWTPs.

Characteristics of Organic Matters Translation and Removal on Sludge Reduction HA-A/A-MCO Process

In order to explore methods of improving phosphorous and nitrogen removal in sludge reduction technologies, an advanced process combining sludge reduction and phosphorous and nitrogen removal was developed, for short, HA-A/A-MCO Process (Hydrolysis-Acidogenosis -Anaerobic/Anoxic-Multistep Continuous Oxic tank). Under the condition of this process achieving favorable effect of phosphorous and nitrogen removal and sludge reduction, test results of the process treating campus wastewater showed that when influent COD was 316-407mg/L, effluent COD was lower than 18mg/L, and COD removal rate exceeded 96%. When return ratio of anaerobic P-release sludge entering into hydrolysis-acidification tank was about 2% of influent flow, most anaerobic P-release sludge was translated into organic matter and it mainly contained VFA(about 275mg/L), which was 4.74 times as much as that(58mg/L) in original sewage. Supernatant which was rich in VFA from hydrolysis-acidification tank entered into subsequent A2/O cells, which could provide affluent carbon source for phosphorous and nitrogen removal.

Application of vibration milling for advanced wastewater treatment and excess sludge reduction

As a new sludge reduction technology with a phosphorus removal mechanism, a vibration milling technology that uses iron balls have been applied to the wastewater treatment process. Three anaerobic-aerobic cyclic activated sludge processes: one without sludge disintegration; one disintegrated sludge by ozonation; and the other disintegrated sludge with the vibrating ball mill were compared. Ozonation achieved the best sludge reduction performance, but milling had the best phosphorus removal. This is because iron was mixed into the wastewater treatment tank due to abrasion of the iron balls, leading to settling of iron phosphates. Thus, the simple means of using iron balls as the medium in a vibrating ball mill can achieve both a sludge reduction of half and excellent phosphorus removal. Material balances in the processes were calculated and it was found that carbon components in disintegrated sludge were more resistant to biological treatment than nitrogen.

Bacteria permeabilisation and disruption caused by sludge reduction technologies evaluated by flow cytometry

Technologies proposed in the last decades for the reduction of the sludge production in wastewater treatment plants and based on the mechanism of cell lysis-cryptic growth (physical, mechanical, thermal, chemical, oxidative treatments) have been widely investigated at lab-, pilot- and, in some cases, at full-scale but the effects on cellular lysis have not always been demonstrated in depth. The research presented in this paper aims to investigate how these sludge reduction technologies affect the integrity and permeabilisation of bacterial cells in sludge using flow cytometry (FCM), which permits the rapid and statistically accurate quantification of intact, permeabilised or disrupted bacteria in the sludge using a double fluorescent DNA-staining instead of using conventional methods like plate counts and microscope. Physical/mechanical treatments (ultrasonication and high pressure homogenisation) caused moderate effects on cell integrity and caused significant cell disruption only at high specific energy levels. Conversely, thermal treatment caused significant damage of bacterial membranes even at moderate temperatures (45–55 °C). Ozonation significantly affected cell integrity, even at low ozone dosages, below 10 mgO 3/gTSS, causing an increase of permeabilised and disrupted cells. At higher ozone dosages the compounds solubilised after cell lysis act as scavengers in the competition between soluble compounds and (particulate) bacterial cells. An original aspect of this paper, not yet reported in the literature, is the comparison of the effects of these sludge reduction technologies on bacterial cell integrity and permeabilisation by converting pressure, temperature and ozone dosage to an equivalent value of specific energy. Among these technologies, comparison of the applied specific energy demonstrates that achieving the complete disruption of bacterial cells is not always economically advantageous because excessive energy levels may be required.

A Proposed Approach for Modeling Sludge Reduction Technologies

A Proposed Approach for Modeling Sludge Reduction Technologies

Underlying Mechanistic Principles, Performance Evaluation and Proposed Modeling Approach for Selected Waste Activated Sludge Reduction Technologies

Underlying Mechanistic Principles, Performance Evaluation and Proposed Modeling Approach for Selected Waste Activated Sludge Reduction Technologies

Underlying Mechanistic Principles and Proposed Modeling Approach for Waste Activated Sludge Reduction Technologies

Underlying Mechanistic Principles and Proposed Modeling Approach for Waste Activated Sludge Reduction Technologies