Volatile Suspended Solids Concentration Research Articles

Statistical Process Analysis and Optimization of an Aerobic SBR Treating an Industrial Estate Wastewater Using Response Surface Methodology (RSM)

In this study, the performance of an aerobic sequencing batch reactor (SBR) removing carbon and nutrient (N & P) from Faraman's industrial wastewater (FIW) was investigated. This study was performed by varying two significant independent variables viz. aeration time and biomass concentration. The experiments were conducted based on a central composite design (CCD) and analyzed using response surface methodology (RSM). The region of exploration for the process was taken as the area enclosed by aeration time (6-24 h) and mixed liquor volatile suspended solid (MLVSS) concentration (2000-7000 mg/l) boundaries. Seven dependent parameters as the process responses were measured and calculated. Direct and interactive effects of th e variables on the responses were described by the models given by RSM. The results showed that the maximum total COD (TCOD) removal of 73.89% was obtained at the highest value of the factors (24 h and 7000 mg/l). The maximum values of total nitrogen (TN) removal efficiency were found to be 36.39%. The low TN removal directed the study to the reduction of oxygen level from 7 to 3 mg/l. The DO reduction with the extended aeration mode resulted in an increase in TN removal while decreased the TCOD, non-biodegradable CO D (nbCOD) and BOD removal efficiencies. The oxygen concentration had diminutive effect on phosphoru s removal.

Posttreatment of UASB Effluents of Tapioca Starch Wastewater Using Downflow Hanging Sponge System

This study is aimed at a performance evaluation of downflow hanging sponge (DHS) systems using mixed fungal and bacterial cultures for posttreatment of upflow anaerobic sludge blanket (UASB) effluents of tapioca starch wastewater. The effects of sludge composition on the microbial activity and effluent organic matter were also investigated. The whole experiment consisted of RUN I and RUN II with hydraulic retention times (HRTs) of 7 and 1 h, respectively, and the organic loading rates (OLR) ranged from 2.0 to 6.0 kg COD/m3 day-1 . The organic removal efficiencies were higher in RUN II, in the 94–96% range for both DHS systems. Under steady-state conditions, the volatile suspended solids (VSS) concentration in the sludge retained in the fungal downflow hanging sponge (FDHS) system showed little change, indicating a balance between the degradation of old biomass and the accumulation of the fresh biomass. Also, there was no significant removal of nitrogen in the FDHS system. However, the nitrogen was reduce...

Submerged Membrane Bioreactor at Substrate‐Limited Conditions: Activity and Biomass Characteristics

A pilot-scale membrane bioreactor was operated for advanced treatment of secondary effluent from a wastewater treatment plant. The performance and biomass characteristics were evaluated under two different hydraulic retention time (HRT) values (7.5 and 15 hours). The system was operated successfully without biomass purge and, after an initial phase, evolved until reaching a constant mixed-liquor volatile suspended solids (MLVSS) concentration, which resulted in the same value of carbon utilization rate (0.067 +/- 0.004 kg COD kg(-1) MLVSS d(-1)) for both HRTs. Respiration tests (maximum and endogenous oxygen uptake rates) confirmed a low microbial activity, which approached constant values (0.32 +/- 0.001 and 0.064 +/- 0.007 g O2 g(-1) MLVSS d(-1), respectively), regardless of the HRT. The sludge morphology and bound and supernatant extracellular polymeric substances also were assessed. Membrane performance was characterized by a stable behavior occurring simultaneously with a high level of biodegradation in the microcolloidal and soluble fraction.

Assessing the Effects of Solids Residence Time and Volatile Fatty Acid Augmentation on Biological Phosphorus Removal Using Real Wastewater

The purpose of the research presented herein was to evaluate the effects of solids residence time (SRT) and organic acid augmentation on biological phosphorus removal (BPR), with a focus on how these operational variables affect key metabolisms and the distribution of the microbial population. Using laboratory-scale sequencing batch reactors seeded with a mixed microbial consortium and fed real wastewater, we observed that longer SRTs can improve BPR performance; organic acid augmentation can stabilize BPR, but it is not necessary for process success; and higher volatile suspended solids concentrations correlate with improved phosphorus removal. The results also suggest that organic acids may not be critical in driving anaerobic phosphorus release, but in driving aerobic growth. Finally, given an observed population similarity across all tested bioreactors, BPR variability appears to be less influenced by the presence of specific microbes and more affected by the induction of critical metabolisms.

Experience of a pilot-scale hydrogen-producing anaerobic sequencing batch reactor (ASBR) treating food waste

A pilot-scale H 2-producing anaerobic sequencing batch reactor (ASBR) treating food waste was operated. During the operation, the carbon/nitrogen (C/N) ratio was adjusted from 10 to 30 by changing the composition of the food waste. When the C/N ratio was lower than 20, the H 2 yield was maintained at around 0.5 mol H 2/mol hexose added, accounting for 2.3% of energy conversion efficiency contained in food waste to H 2, but it gradually dropped at higher C/N ratios. The low performance was accompanied by increased production of lactate, propionate, and valerate. In order to recover the performance, alkaline shock (pH 12.5 for 1 day) was imposed on the entire mixed liquor in the fermenter. This alkaline shock method was so effective that the H 2 yield significantly increased to over 0.9 mol H 2/mol hexose added, and was then stabilized at 0.69 mol H 2/mol hexose added. In addition, the settling characteristics of H 2-producing ASBR, which was separated into three layers, were investigated. Ribonucleic acid (RNA) as well as volatile suspended solid concentrations of each layer were measured to suggest how to enhance the H 2 production in ASBR operation.

Effect of Using Effective Microorganisms EM-1 on the Performance of Extended Aeration Activated Sludge in Treating Domestic Wastewater

This research concerning with the effect of using the effective microorganisms on the efficiency of extended Aeration Activated Sludge Units which consist from many strain of Bacteria, Fungi and Actinomycetes in addition to board spectrum of nutrient and elements which important to growth, The use of this product is practically applied by using two bench scale laboratory units where they are operated to treat the wastewater after completing and preparing the activated sludge units to work under the same conditions of temperature and detention time (DT).
 One bench scale is fed with wastewater and the other is operated by using a mixture of EM-1 along with the wastewater. It is noticed that the use of EM-1 with wastewater has reduced the smell resulting from disintegration in the aeration basin. Further, the color of sludge in the unit where EM-1 is added is light brown which means more activity and vitality. Besides, the concentration of mixed liquor volatile suspended solids (MLVSS) is increased by using EM-1 by 30% due to the increase of nutrients and a reduction in the sludge volume index (SVI) which is an important factor in the performance of the secondary settling basins which means a reduction in bulking of sludge, which is considered one of the most notable operating problem in activated sludge units. As a result bulking of sludge reduced by25% when EM-1 is used. Thus, EM-1 has participated in solving three important operating problems suffered by operators of these treatment units easily and without using complicated technologies or appliances. Further, EM-1 improves the removal efficiency of the units about 6-8% due to the reduction in chemical oxygen demand in the treated wastewater leaving the unit by 32%.

Effect of Using Effective Microorganisms EM-1 on the Performance of Extended Aeration Activated Sludge in Treating Domestic Wastewater

This research concerning with the effect of using the effective microorganisms on the efficiency of extended Aeration Activated Sludge Units which consist from many strain of Bacteria, Fungi and Actinomycetes in addition to board spectrum of nutrient and elements which important to growth, The use of this product is practically applied by using two bench scale laboratory units where they are operated to treat the wastewater after completing and preparing the activated sludge units to work under the same conditions of temperature and detention time (DT). 54 One bench scale is fed with wastewater and the other is operated by using a mixture of EM-1 along with the wastewater. It is noticed that the use of EM-1 with wastewater has reduced the smell resulting from disintegration in the aeration basin. Further, the color of sludge in the unit where EM-1 is added is light brown which means more activity and vitality. Besides, the concentration of mixed liquor volatile suspended solids (MLVSS) is increased by using EM-1 by 30% due to the increase of nutrients and a reduction in the sludge volume index (SVI) which is an important factor in the performance of the secondary settling basins which means a reduction in bulking of sludge, which is considered one of the most notable operating problem in activated sludge units. As a result bulking of sludge reduced by25% when EM-1 is used. Thus, EM-1 has participated in solving three important operating problems suffered by operators of these treatment units easily and without using complicated technologies or appliances. Further, EM-1 improves the removal efficiency of the units about 6-8% due to the reduction in chemical oxygen demand in the treated wastewater leaving the unit by 32%.

Assessment of aerobic and anaerobic stabilization for biological waste sludges from leather and textile industries

Sludges from wastewater treatment plants are considered hazardous waste unless they are adequately stabilized to decrease total and dissolved organic carbon (TOC and DOC) concentrations below the standards for disposal of wastes into landfills. There are several methods to define stabilized sludge such as specific volatile suspended solids (VSS) load or leveling off of the VSS concentration. However, evaluation of sludge stabilization may not be as straightforward as these methods suggest. In this study, aerobic and anaerobic stabilization were applied to industrial sludges from two different industries (i.e., leather and textile) to decrease organic content of the sludges below hazardous waste levels. Aerobic sludge treatment provided better organics removals compared to anaerobic sludge treatment for leather industry with a VSS removal of 38% and a TOC removal of 65%. For textile industry, both aerobic and anaerobic treatment resulted in similar decreases in VSS (∼ 50%) and TOC (∼ 60%) concentrations. Although aerobic sludge stabilization was established after approximately 30 days for both leather and textile industries, as suggested by specific VSS loads, organic content of stabilized sludges did not decrease sufficiently to comply with the TOC/DOC standards for landfill disposal and stabilized sludges are still classified as hazardous waste.

Free Water Content and Sludge Retention Time: Impact on Oxygen Transfer in Activated Sludge

To investigate the effect of sludge retention time (SRT) and the concentration of mixed liquid volatile suspended solids (MLVSS) on oxygen transfer in activated sludge, we studied mass transfer coefficients (k(L)a) in a pilot-scale membrane bioreactor, which treated synthetic greywater. Additionally, experiments with iron hydroxide flocs were performed to examine the role of free water content in oxygen transfer. The results demonstrate that the alpha-factor is reduced when free water content decreases and floc volume increases. Because the MLVSS concentration in activated sludge mainly regulates floc volume, a reduction of oxygen transfer with increasing MLVSS concentration was observed. If the floc volume remains unchanged, oxygen transfer increases with increasing SRT.

Microbial enzymatic activities in a pilot-scale MBR experimental plant under different working conditions

Phosphatases, glucosidase, protease, esterase and dehydrogenase activities in a MBR (membrane bioreactor) system equipped with ultrafiltration membranes for the treatment of real urban wastewater were measured at different volatile suspended solid (VSS) concentrations, total suspended solid (TSS) concentrations, hydraulic retention times (HRT), temperatures and inflow rates. The results showed the capacity of the MBR system to remove COD and BOD 5 at TSS between 7200 and 13,300 mg/L; HRT values of 8.05 and 15.27 h; inflow rates of 14.67 and 27.81 L/h; and temperatures between 4 and 27 °C. The enzymatic activities are influenced by increases in VSS and TSS concentrations. These results suggest that the ability to get adapted to environmental changes of the bacterial populations and their microbial enzymatic activities is essential to understand the biological processes that occur in MBR systems and crucial for proper urban wastewater treatment when using MBR technologies.

Microbial community structure and dynamics in a pilot-scale submerged membrane bioreactor aerobically treating domestic wastewater under real operation conditions

A pilot scale submerged ultra-filtration membrane bioreactor (MBR) was used for the aerobic treatment of domestic wastewater over 9 months of year 2006 (28th March to 21st December). The MBR was installed at a municipal wastewater facility (EMASAGRA, Granada, Spain) and was fed with real wastewater. The experimental work was divided in 4 stages run under different sets of operation conditions. Operation parameters (total and volatile suspended solids, dissolved oxygen concentration) and environmental variables (temperature, pH, COD and BOD 5 of influent water) were daily monitored. In all the experiments conducted, the MBR generated an effluent of optimal quality complying with the requirements of the European Law (91/271/CEE 1991). A cultivation-independent approach (polymerase chain reaction-temperature gradient gel electrophoresis, PCR-TGGE) was used to analyze changes in the structure of the bacterial communities in the sludge. Cluster analysis of TGGE profiles demonstrated significant differences in community structure related to variations of the operation parameters and environmental factors. Canonical correspondence analysis (CCA) suggested that temperature, hydraulic retention time and concentration of volatile suspended solids were the factors mostly influencing community structure. 23 prominent TGGE bands were successfully reamplified and sequenced, allowing gaining insight into the identities of predominantly present bacterial populations in the sludge. Retrieved partial 16S-rRNA gene sequences were mostly related to the α-Proteobacteria, β-Proteobacteria and γ-Proteobacteria classes. The community established in the MBR in each of the four stages of operation significantly differed in species composition and the sludge generated displayed dissimilar rates of mineralization, but these differences did not influence the performance of the bioreactor (quality of the permeate). These data indicate that the flexibility of the bacterial community in the sludge and its ability to get adapted to environmental changes play an important role for the stable performance of MBRs.

Development and validation of a rapid method for the determination of tetracycline in activated sludge by SPE clean‐up and HPLC–UV detection

The aim of this study was to develop and validate a rapid analytical method for tetracycline (TC) determination in activated sludge. The analytical method developed is applicable on activated sludge containing a volatile suspended solid concentration below 10 g l−1, which nearly includes all wastewater treatment plants and the major proportion of membrane bioreactors. The analytical method included two steps: sample clean‐up followed by high‐performance liquid chromatography (HPLC) with ultraviolet (UV) detection analysis. Prior to the analysis, TC was extracted from the matrix by a mixture of EDTA and McIlvaine buffer. Sample clean‐up was carried out by solid phase extraction (SPE) with strong anion exchange (SAX) cartridges. SAX cartridges retained organic matters interfering with TC. Analysis was performed by HPLC–UV with a gradient elution. The method was validated as the R 2 value was 0.9991 for the calibration curve. Recoveries were between 92% (± 6%) and 103% (± 9%). The limit of detection (LOD) and the limit of quantification (LOQ) were 0.1 mg l−1 and 0.5 mg l−1, respectively. Accuracy was not entirely satisfactory, but should be related to the complexity of the matrix, which is a hindrance to the precision of the method. The method was also validated on industrial samples.

Effect of biomass concentration on the performance of a MBR system: Studies of microbial communities

The performance of a bench-scale submerged membrane bioreactor (MBR) equipped with ultrafiltration membranes (Zenon®) was investigated for the treatment of domestic wastewater under different mixed liquor suspended solid (MLSS) concentration. The results showed the capacity of the MBR systems to remove high concentration in organic matter (COD and BOD5) in order to study the influence of the removal in organic matter enzymatic activities (acid and alkaline phosphatases, glucasidase, protease, esterase and dehydrogenase); and biodiversity of the bacterial community in the sludge was measured. Cluster analysis of the temperature gradient gel electrophoresis profiles demonstrated that the community composition varied significantly in the different experiments. Depending on MLSS and temperature, the bacterial community experienced sequential shifts as the biomass accumulated, as shown by the evolution of the population profiles through time as volatile suspended solids concentration.

A two‐stage process for simultaneous thermophilic sludge digestion, pathogen control and metal leaching

A consortium of aerobic sulphur oxidizing microorganisms native to municipal sewage sludge has been developed that is capable of reducing the pH of sludge from 7.0 to 2.0 under mild‐thermophilic (45 °C) temperatures. This mild‐thermophilic, acidophilic acclimatized consortium has then been used to develop a thermophilic acidophilic culture capable of reducing the pH of municipal sewage sludge from 7.0 to 4.8 at 60 °C. Furthermore, these two cultures have been used to develop a novel two‐stage aerobic process functioning under thermophilic and mild‐thermophilic conditions capable of simultaneous sludge digestion, pathogen control and metal leaching. Studies with 1.5 L reactors indicate that at the end of the process, concentration of volatile suspended solids has stabilized, no coliforms are present, and 90–98% copper, 90–94% manganese and 95–100% zinc has been leached.

Biological hydrogen production in an anaerobic sequencing batch reactor: pH and cyclic duration effects

An anaerobic sequencing batch reactor (ASBR) was used to evaluate biological hydrogen production from carbohydrate-rich organic wastes. The goal of the proposed project was to investigate the effects of pH (4.9, 5.5, 6.1, and 6.7), and cyclic duration (4, 6, and 8 h) on hydrogen production. With the ASBR operated at 16-h HRT, 25 g COD/L, and 4-h cyclic duration, the results showed that the maximum hydrogen yield of 2.53 mol H 2/mol sucrose consumed appeared at pH 4.9. The carbohydrate removal efficiency declined to 56% at pH 4.9, which indirectly resulted in the reduction of total volatile fatty acid production. Acetate fermentation was the dominant metabolic pathway at pH 4.9. The concentration of mixed liquor volatile suspended solid (MLVSS) also showed a decrease from nearly 15,000 mg/L between pHs 6.1 and 6.7 to 6000 mg/L at pH 4.9. Investigation of the effect of cyclic duration found that hydrogen yield reached the maximum of 1.86 mol H 2/mol sucrose consumed at 4-h cyclic duration while ASBR was operating at 16-h HRT, 15 g COD/L, and pH 4.9. The experimental results showed that MLVSS concentration increased from 6200 mg/L at 4-h cyclic duration to 8500 mg/L at 8-h cyclic duration. However, there was no significant change in effluent volatile suspended solid concentration. The results of butyrate to acetate ratio showed that using this ratio to correlate the performance of hydrogen production is not appropriate due to the growth of homoacetogens. In ASBR, the operation is subject to four different phases of each cycle, and only the complete mix condition can be achieved at react phase. The pH and cyclic duration under the unique operations profoundly impact fermentative hydrogen production.

Circulating fluidized bed biological reactor for nutrients removal

A new biological nitrogen removal process, which is named herein “The circulating fluidized bed bioreactor (CFBBR)”, was developed for simultaneous removal of nitrogen and organic matter. This process was composed of an anaerobic bed (Riser), aerobic bed (Downer) and connecting device. Influent and nitrified liquid from the aerobic bed enters the anaerobic bed from the bottom of the anaerobic bed, completing the removal of nitrogen and organic matter. The system performance under the conditions of different inflow loadings and nitrified liquid recirculation rates ranging from 200% to 600% was examined. From a technical and economic point of view, the optimum nitrified liquid recirculation ratewas 400%. With a shortest total retention time of 2.5 h (0.8 h in the anaerobic bed and 1.5 h in the aerobic bed) and a nitrified liquid recirculation rate of 400% based on the influent flow rate, the average removal efficiencies of total nitrogen (TN) and soluble chemical oxygen demand (SCOD) were found to be 88% and 95%, respectively. The average effluent concentrations of TN and SCOD were 3.5 mg/L and 16 mg/L, respectively. The volatile suspended solid (VSS) concentration, nitrification rate and denitrification rate in the system were less than 1.0 g/L, 0.026-0.1 g NH4+-N/g VSS·d, and 0.016–0.074 g NOx−-N/g VSS·d, respectively.

Improved Computational Model (AQUIFAS) for Activated Sludge, Integrated Fixed‐Film Activated Sludge, and Moving‐Bed Biofilm Reactor Systems, Part III: Analysis and Verification

Research was undertaken to analyze and verify a model that can be applied to activated sludge, integrated fixed-film activated sludge (IFAS), and moving-bed biofilm reactor (MBBR) systems. The model embeds a biofilm model into a multicell activated sludge model. The advantage of such a model is that it eliminates the need to run separate computations for a plant being retrofitted from activated sludge to IFAS or MBBR. The biofilm flux rates for organics, nutrients, and biomass can be computed by two methods-a semi-empirical model of the biofilm that is relatively simpler, or a diffusional model of the biofilm that is computationally intensive. Biofilm support media can be incorporated to the anoxic and aerobic cells, but not the anaerobic cells. The model can be run for steady-state and dynamic simulations. The model was able to predict the changes in nitrification and denitrification at both pilot- and full-scale facilities. The semi-empirical and diffusional models of the biofilm were both used to evaluate the biofilm flux rates for media at different locations. The biofilm diffusional model was used to compute the biofilm thickness and growth, substrate concentrations, volatile suspended solids (VSS) concentration, and fraction of nitrifiers in each layer inside the biofilm. Following calibration, both models provided similar effluent results for reactor mixed liquor VSS and mixed liquor suspended solids and for the effluent organics, nitrogen forms, and phosphorus concentrations. While the semi-empirical model was quicker to run, the diffusional model provided additional information on biofilm thickness, quantity of growth in the biofilm, and substrate profiles inside the biofilm.

Effect of Aeolosoma hemprichi on excess activated sludge reduction

In order to stabilize the growth of A. hemprichi and minimize the sludge production through biological predation, A. hemprichi was inoculated in batch and continuous experiments to investigate the growth characteristics and the effect on sludge reduction in this study. Various available volatile suspended solid (AVSS) concentrations were obtained after the ultrasonic irradiation on pre-sterilized sludge. It was found the density of A. hemprichi was proportionate to AVSS concentration. A. hemprichi reached the maximum density when AVSS concentration was more than 3000 mg/L. No obvious difference was found between the initial specific growth ratio ( μ) of A. hemprichi at various AVSS concentrations. When N > 0.5 N L, μ decreased with the increase of A. hemprichi and Logistic model was adopted to fit the growth of A. hemprichi. Sludge reduction rate was correlated with both the growth rate and the density of A. hemprichi. The results indicated the sludge reduction rate was maximum at the density of 315 ind./mL. Sludge retention time (SRT) could effectively control the growth density of A. hemprichi in continuous tests.

Comparative evaluation of the microbial community in biological processes treating industrial and domestic wastewaters

Comparison of the microbial composition and process performance between laboratory scale processes treating domestic and vegetable oil wastewaters. Two laboratory scale modified Ludzack-Ettinger processes were operated under similar operating conditions. One process was fed domestic wastewater and the other an industrial wastewater, vegetable oil effluent. Nitrogen removal capacities of the processes were similar. The industrial process exhibited a lower COD removal capacity and oxygen utilization rate, although a greater mixed liquor volatile suspended solids concentration was observed in the industrial process. Fluorescent in situ hybridization (FISH) with probes EUBmix, ALF1b, BET42a, GAM42a and HGC69a revealed that 81% and 72% of total cells stained with 4', 6-diamidino-2-phenylindole (DAPI) within the domestic and industrial processes respectively bound to EUBmix. This indicated a slightly lower Eubacterial population within the industrial process. The alpha-proteobacteria was the dominant community in the industrial process (31% of EUBmix), while the beta-proteobacteria dominated the domestic process (33% of EUBmix). The findings served to establish a difference in the microbial population between the processes. Therefore, the class alpha-proteobacteria could play a primary role in the degradation of vegetable oil effluent. This research will aid in process design and retrofitting of biological processes treating vegetable oil effluent.

Estimation of the fraction of biologically active methyl tert-butyl ether degraders in a heterogeneous biomass sample

The fraction of biologically active methyl tert-butyl ether degraders in reactors is just as important for prediction of removal rates as knowledge of the kinetic parameters. The fraction of biologically active methyl tert-butyl ether degraders in a heterogeneous biomass sample, taken from a packed bed reactor, was determined using a batch kinetic based approach. The procedure involved modeling of methyl tert-butyl ether removal rates from batch experiments followed by parameter estimations. It was estimated to be 5-14% (w/w) of the measured volatile suspended solids concentration in the reactor.