Sludge Reduction Process Research Articles

Effects of dissolved oxygen on performance and microbial community structure in a micro-aerobic hydrolysis sludge in situ reduction process

A sludge process reduction activated sludge (SPRAS), with a sludge process reduction module composed of a micro-aerobic tank and a settler positioned before conventional activated sludge process, showed good performance of pollutant removal and sludge reduction. Two SPRAS systems were operated to investigate effects of micro-aeration on sludge reduction performance and microbial community structure. When dissolved oxygen (DO) concentration in the micro-aerobic tank decreased from 2.5 (SPH) to 0.5 (SPL) mg/L, the sludge reduction efficiency increased from 42.9% to 68.3%. Compared to SPH, activated sludge in SPL showed higher contents of extracellular polymeric substances and dissolved organic matter. Destabilization of floc structure in the settler, and cell lysis in the sludge process reduction module were two major reasons for sludge reduction. Illumina-MiSeq sequencing showed that microbial diversity decreased under high DO concentration. Proteobacteria, Bacteroidetes and Chloroflexi were the most abundant phyla in the SPRAS. Specific comparisons down to the class and genus level showed that fermentative, predatory and slow-growing bacteria in SPL community were more abundant than in SPH. The results revealed that micro-aeration in the SPRAS improved hydrolysis efficiency and enriched fermentative and predatory bacteria responsible for sludge reduction.

High-Rate Anaerobic Side-Stream Reactor (ASSR) Processes to Minimize the Production of Excess Sludge.

High-rate anaerobic side-stream reactor (ASSR) processes were developed to minimize excess sludge production during wastewater treatment. New ASSRs were operated in 2.5-day solids retention time (SRT), much shorter than 10-day SRT used by the commercial sludge reduction process. The 2.5-day was selected based on literature review and preliminary studies, showing that maximum solublization of key floc components, such as divalent cations, extracellular polymeric substances (EPS), and protease, occur within 2 to 3 days of anaerobic digestion. The laboratory reactor study showed that 2.5-day ASSR systems produced approximately 60 and 20% less sludge than the control (no ASSR) and the 10-day ASSR, respectively. The experimental systems showed acceptable effluent quality, despite minimal sludge wastage. This was possible because sludge EPS were continuously released/degraded and regenerated as sludge underwent recirculation between ASSR and the aerobic basin. The results supported that the activated sludge process incorporating small ASSRs significantly decrease the production of excess sludge during wastewater treatment.

Microbial community structure of anoxic–oxic-settling-anaerobic sludge reduction process revealed by 454-pyrosequencing

To understand process performance and microbial community structure in oxic-settling-anaerobic (OSA) sludge reduction process, an anoxic–OSA (A+OSA) system and a conventional anoxic–oxic (AO) system were operated for 200days. Both systems were almost equally effective in the removal of COD and ammonium nitrogen, but A+OSA system showed higher nitrogen removal efficiency owing to denitrification and the release of soluble organic matters in the sludge holding tank (SHT). A+OSA process reduced sludge production by 30.4% with observed sludge yield of 0.179gSS/gCOD. Pyrosequencing results revealed that although core populations were shared with highly functional organization, the relative abundance and stability of microbial communities in A+OSA system were higher than AO system. Classes Anaerolineae and Actinobacteria responsible for hydrolysis and fermentation of organic matters were enriched in SHT and played an important role in sludge reduction of A+OSA process. Specific comparison down to the genus level revealed the enrichment of anaerobic fermentative bacteria (Azospira, Propionivibrio and Sulfuritalea) and slow growers (Trichococcus) in A+OSA system.

Microbial community in anoxic-oxic-settling-anaerobic sludge reduction process revealed by 454 pyrosequencing analysis.

Modification of the anoxic-oxic (AO) process by inserting a sludge holding tank (SHT) into the sludge return line forms an anoxic-oxic-settling-anaerobic (A+OSA) process that can achieve a 48.98% sludge reduction rate. The 454 pyrosequencing method was used to obtain the microbial communities of the AO and A+OSA processes. Results showed that the microbial community structures of the 2 processes were different as a result of the SHT insertion. Bacteria assigned to the phyla Proteobacteria and Bacteroidetes commonly existed and dominated the microbial populations of the 2 processes. However, the relative abundance of these populations shifted in the presence of SHT. The relative abundance of Proteobacteria decreased during the A+OSA process. A specific comparison at the class level showed that Sphingobacteria was enriched in the A+OSA process. The result suggested that the fermentative bacteria Sphingobacteria may have key functions in reducing the sludge from the A+OSA process. Uncultured Nitrosomonadaceae gradually became the dominant ammonia-oxidizing bacteria, and the nitrite-oxidizing bacterium Nitrospira was enriched in the A+OSA process. Both occurrences were favorable for stabilized nitrogen removal. The known denitrifying species in the A+OSA process were similar to those in the AO process; however, their relative abundance also decreased.

Alkaline treatment of high-solids sludge and its application to anaerobic digestion.

High-solids anaerobic digestion is a promising new process for sludge reduction and bioenergy recovery, requiring smaller digestion tanks and less energy for heating, but a longer digestion time, than traditional low-solids anaerobic digestion. To accelerate this process, alkaline sludge disintegration was tested as a pretreatment method for anaerobic digestion of high-solids sludge. The results showed that alkaline treatment effectively disintegrated both low-solids sludge and high-solids sludge, and treatment duration of 30 min was the most efficient. The relation between sludge disintegration degree and NaOH dose can be described by a transmutative power function model. At NaOH dose lower than 0.2 mol/L, sludge disintegration degree remained virtually unchanged when sludge total solids (TS) content increased from 2.0 to 11.0%, and decreased only slightly when sludge TS increased to 14.2%. Although high-solids sludge required a slightly higher molarity of NaOH to reach the same disintegration level of low-solids sludge, the required mass of NaOH actually decreased due to sludge thickening. From the view of NaOH consumption, sludge TS of 8-12% and a NaOH dose of 0.05 mol/L were optimum conditions for alkaline pretreatment, which resulted in a slight increase in accumulative biogas yield, but a decrease by 24-29% in digestion time during the subsequent anaerobic digestion.

A micro-aerobic hydrolysis process for sludge in situ reduction: Performance and microbial community structure

A sludge process reduction activated sludge (SPRAS) system by inserting a sludge process reduction (SPR) module, composed of a micro-aerobic tank and a settler, before activated sludge process was operated for sludge in situ reduction. The average removal efficiencies of COD and ammonium nitrogen were 86.6% and 87.9%, respectively. Compared to anoxic/aerobic (AO) process, SPRAS process reduced sludge production by 57.9% with observed sludge yield of 0.076gVSS/gCOD. Pyrosequencing analyses revealed that the relative abundance and stability of microbial communities in SPRAS system were higher than AO system. Fermentative acidogenic classes Anaerolineae, Actinobacteria, Cytophagia and Caldilineae were enriched in the SPR module and responsible for sludge reduction. Specific comparison down to the genus level identified the enrichment of oxyanion-reducing bacteria (Sulfuritalea; Azospira; Ramlibacter), fermentative acidogenic bacteria (Propionivibrio; Opitutus; Caldilinea), slow growers (Ramlibacter) and predatory bacteria (Myxobacteria) in SPRAS system. Nitrifiers were also more abundant in SPRAS system than AO system.

Characterization of dissolved organic matter in the anoxic–oxic-settling-anaerobic sludge reduction process

Abstract Three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy and gel permeation chromatography (GPC) analysis were employed to investigate the distribution and transformation of dissolved organic matter (DOM) in the anoxic–oxic-settling-anaerobic (A + OSA) process for sludge reduction. The A + OSA process showed a good performance in nitrogen and organic pollutants removal efficiency, and reduced sludge yield by 32% under a sludge retention time of 6 h in the anaerobic sludge holding tank (SHT). Parallel factor analysis was used to assess DOM composition from EEM spectra and three fluorescent components were identified: two humic-like components and one protein-like component. In the A + OSA process, the humic-like components were difficult to degraded, while the protein-like component was easily hydrolyzed and adsorbed under anoxic conditions. The fluorescence intensities of the humic-like and protein-like components were both strengthened in the SHT owing to sludge decay under the anaerobic condition. GPC analysis of the A + OSA system showed that the majority of molecules in the influent wastewater with molecular weight (MW) in the range of >250 and 30–50 kDa were mainly transformed into small molecules with MW in the range of 30–250 and

Sludge reduction and performance analysis of a modified sludge reduction process

A modified sludge process reduction activated sludge (SPRAS) technology was developed by inserting a sludge process reduction (SPR) module, composed of an aeration tank and a settler, before the activated sludge system was proposed in this study. Compared with the anaerobic/anoxic/aerobic (AAO) process, the SPRAS resulted in a remarkable decrease in sludge production by 76.6%; sludge decay owing to lengthy solids retention time (about 121.5 d) could be the major cause. During the 217-day operation, the oxidation-reduction potential (ORP) (from 54 to -198 mV) and pH (from 7.8 to 5.0) at the bottom of the SPR settler gradually decreased, and low ORP and pH were in favor of sludge reduction in the SPRAS system. The insertion of the SPR module improved the removal efficiencies of suspended solids, chemical oxygen demand and ammonium nitrogen, and total nitrogen concentration in the effluent was reduced from 23.89 ± 4.82 to 14.16 ± 3.98 mg/L by 50% influent bypassing the SPR module. These results indicated that the SPRAS process could produce much less excess sludge and guarantee better effluent quality than the AAO process.

The Research Progress on Oxic-Settling-Anaerobic Sludge Reduction Process

The research progress on the oxic-settling-anaerobic sludge reduction process at home and abroad was reviewed, which was focused on the progress of sludge reduction mechanism, operating performance, impact factors and microbiological characteristics of OSA process. Then the shortcomings of the OSA process were analyzed and its development was also predicted.

Study on a novel reactor of sludge process reduction for domestic sewage treatment

A laboratory-scale novel Sludge Reduction Reactor with Arc Guide Plate (SRR) for sludge process reduction was developed in this study. Pollutant removal efficiency and biomass yield for domestic sewage treatment in the Anaerobic/Anoxic/Oxic-SRR (A2/O-SRR) process were compared with performances in a control A2/O process. One of the competitive advantages in the SRR was that part of the inert suspended solids (ISS) could be separated and discharged out of system with flux at the bottom of the SRR. Mixed liquid volatile suspended solids (MLVSS) in the A2/O-SRR system also could be steadily kept at a good level under a relatively long solid retention time. The average MLVSS/mixed liquor suspended solids (MLSS) ratio of 77.5% in the A2/O-SRR was higher than that in the A2/O process. Average removal rates of chemical oxygen demand (COD), total nitrogen (TN) and showed little difference, while total phosphorous (TP) removal efficiency in the A2/O-SRR decreased slightly (81.89% in the A2/O-SRR and 86.50% in the A2/O process) due to the reduction of sludge discharge. The A2/O-SRR system demonstrated a considerable sludge reduction effect, with the sludge reduction ratio of 43.8%, lower solid volume index and higher dehydrogenase activity (DHA) value in comparison to the control A2/O system. The mainly mechanisms of sludge reduction in the SRR have been proved to be the uncoupling effect under the condition of anaerobic/oxic circulation and the sludge lysis with the lack of substrate.

Bacterial Community Structure of HA-A/A-MCO Sludge Reduction Process

Bacterial Community Structure of HA-A/A-MCO Sludge Reduction Process

Removal of Phosphorus and Recovery in Advanced HA-A/A-MCO Sludge Reduction Process

Removal of Phosphorus and Recovery in Advanced HA-A/A-MCO Sludge Reduction Process

Three-Dimensional Fluorescence Characteristics of HA-A/A-MCO Sludge Reduction Process

Three-Dimensional Fluorescence Characteristics of HA-A/A-MCO Sludge Reduction Process

The influence of SRT on phosphorus removal and sludge characteristics in the HA–A/A–MCO sludge reduction process

By researching the influence of sludge age (SRT) on phosphorous removal and sludge characteristics in the HA–A/A–MCO (hydrolysis-acidification–anaerobic/anoxic–multistep continuous oxic tank) process, which has the effect of simultaneous phosphorous and nitrogen removal and sludge reduction, it is found that extended SRT is helpful for improving the ability of anaerobic phosphorous release and chemical recovery of phosphate, but the hosphorous removal efficiency is not affected. Extended SRT causes the system to have even more active sludge; it can also lead to the system having a powerful ability of biochemical reaction by using superiority of concentration. Meanwhile, extended SRT can still reduce sludge yield. Extended SRT cannot make soluble metabolic product (SMP) accumulate in the reactor, so that the pollutant removal power is reduced; it also cannot affect the activity of the sludge. However, extended SRT is able to make the coagulation of the sludge hard, and cause the sludge volume index value increase, but cannot cause sludge bulking.

Influence of Organic Load on Phosphorous Release and Absorption in HA-A/A-MCO Sludge Reduction Process

When organic load of mixed liquid is up to a certain value, organic matter content is not the restrictive factor of phosphorus release any more. Optimum organic load for phosphorous anaerobic release in HA-A/A-MCO process is 0.141gCOD/gMLSS.d. Sufficient phosphorus release in anaerobic phase is the premise that high efficiency phosphorus absorption can be obtained in anaerobic phase. The maximum of releasable phosphorus sludge per unit weight (Pm/M) in HA-A/A-MCO process is 5.7mgP/gMLSS

DGGE Analysis Bacterial Community Structure of Advanced Sludge Reduction Process

Bacterial community structure of advanced HA-A/A-MCO sludge reduction process is analyzed by DGGE fingerprinting technology. Research results indicates that microbial flora showed the distinction of highly diversity in anaerobic tank, anoxic tank and MCO tank of the HA-A/A-MCO process, and each tank has its own diversified and stable dominant microorganisms, as so the co-activation of such preponderant bacterial community promotes the system to exert favourable and consistent function of phosphorous and nitrogen removal and sludge reduction.

Investigation of a new anaerobic side-stream reactor (ASSR) process for sludge reduction in biological wastewater treatment

Investigation of a new anaerobic side-stream reactor (ASSR) process for sludge reduction in biological wastewater treatmentPreliminary research on the anaerobic side-stream reactor (ASSR) process and examination of literature led us to develop the hypothesis that deflocculation and subsequent sludge hydrolysis occur more effectively under the short period of anaerobic digestion and that recirculation of this sludge back to the aeration basin could lead to more effective excess sludge reduction. To verify this...Author(s)Dong-Hyun ChonChul ParkSourceProceedings of the Water Environment FederationDocument typeConference PaperPublisherWater Environment FederationPrint publication date Mar, 2012ISSN1938-6478DOI10.2175/193864712811694145Volume / Issue2012 / 2Content sourceResiduals and Biosolids ConferenceCopyright2012Word count286

Optimization of operating parameters for sludge process reduction under alternating aerobic/oxygen-limited conditions by response surface methodology

Batch tests were employed to estimate the optimal conditions for excess sludge reduction under an alternating aerobic/oxygen-limited environment using response surface methodology. Three key operating parameters, initial mixed liquor suspended solids (initial MLSS), HRT (hydraulic retention time) and reaction temperature (T), were selected, and their interrelationships studied by the Box–Behnken design. The experimental data and ANOVA analysis showed that the coefficient of determination (R2) was 0.9956 and the adjR2 was 0.9912, which demonstrates that the modified model was significant. The optimum conditions were predicted to give a maximal ΔMLSS yield of 226mg/L at an initial MLSS of 10,021±50mg/L, an HRT of 9.1h and a reaction temperature of 29°C. The prediction was tested by triplicate experiments, where a ΔMLSS yield of 233mg/L was achieved under the chosen optimal conditions. This excellent correlation between the predicted and measured values provides confidence in the model.

Impact of copper and cadmium on aerobic and anaerobic digestibility of sonicated sludge

The effects of the introduction of a sludge reduction process such as ultrasound on batch aerobic and anaerobic biodegradability after exposition to two metals (copper and cadmium) were investigated. The specific energy of ultrasonic treatment applied to the sludge was 200,000 kJ kg TS(-1). Ultrasonic treatment led to floc size reduction and to organic matter solubilization. Low copper (< 5 mg L(-1)) and cadmium (< 1 mg L(-1)) concentration improved aerobic biodegradability. For high metal concentration the maximal instantaneous biogas production rate q(max) inhibition by copper and cadmium was modeled by a saturation-type relationship under aerobic and anaerobic conditions. Under aerobic conditions, respiration inhibition was not affected by sonication. Cadmium inhibition (74%) was more than copper (58%). The positive effect of sonication on CO2 production was maintained after metal introduction. Under anaerobic conditions, metal introduction cancelled out the positive effect of the treatment. The sonicated sludge was 16% less sensitive to copper inhibition but 10% more sensitive to cadmium inhibition compared to non sonicated sludge.

Sludge disintegration during heat treatment at low temperature: A better understanding of involved mechanisms with a multiparametric approach

Although many information is currently available about sludge minimization processes in wastewater treatment plant (WWTP), few data are available about their fundamental mechanisms especially microbial changes. In order to clarify the relationship between sludge reduction efficiency and both chemical and biological modifications, the effects of thermal treatment on activated sludge were investigated by combining the monitoring of cell lysis using flow cytometry (FCM), organic matter solubilization, floc structure and biodegradability. For the maximal temperature (95 °C) applied, COD, proteins, HLS and sugars solubilization degrees reached 12.4 (±1.3)%, 18.6 (±1.8)%, 9.6 (±1)% and 7.4 (±1.9)%, respectively, showing clearly the transfer of organic matter from the particulate to the soluble fraction of the sludge. The results from FCM analysis showed that thermal treatment induces a progressive cell lysis when increasing temperature from 50 to 95 °C. However, the impact on floc structure seemed to be limited as floc destructuration was limited to the temperature elevation at 50 °C. Above 50 °C floc size distribution remained almost constant. The results from biodegradability tests did not show any improvement of the intrinsic biodegradability after the thermal treatment. Only the increase of the specific digestion rate was observed. This study which provides a complete investigation of chemical, physical and biological effects of thermal treatment allows a better knowledge of fundamental mechanisms involved during heat treatment to improve sludge reduction processes.