Simultaneous Organic Carbon Removal Research Articles

Full nitrogen and phosphorus removal in the PASDEBPR system

Photo-activated sludge (PAS) system aims to utilize microalgae to deliver oxygen for bacterial respiration, eliminating the need for external aeration. However, research on the treatment potential of PAS systems in the removal of nutrients is limited. In this context, a research study was devised to evaluate the possibility of developing a microalgae-bacteria consortium to achieve the simultaneous removal of organic carbon, nitrogen, and phosphorus. A successful PAS system capable of removing phosphorus was established at the end of the first phase, with an effluent phosphorus (P) concentration of 1.6 mg P L−1. In the subsequent stage, during the introduction of the nitrification-denitrification process, the system lost stability and deteriorated. Interestingly the system recovered via the sparging of nitrogen gas reaching effluent concentrations of 1.22 mg P L−1 and 0.88 mg N L−1. Thus, the system was capable of removing phosphorus and nitrogen via biological means without the need for external aeration. It is hypothesized that the inhibition caused was due to the production of a gaseous compound during the nitrification/denitrification process.

Anoxic-Aerobic-Anoxic sequencing batch reactor for enhanced nitrogen removal

An anoxic-aerobic-anoxic process was established to achieve simultaneous removal of organic carbon and nitrogen from wastewater in a sequencing batch reactor. The optimum conditions were attained at a DO of 1.5 mg/L with 1 h pre-anoxic and post-anoxic periods. TOC, NH4+-N, and TN removal efficiencies were 98.76 ± 0.95 %, 98.52 ± 0.48 %, and 88.23 ± 0.62 %, respectively, at optimum conditions. Breakpoints in the pH, DO, and ORP curves provided a clear understanding of biochemical reactions happening in the reactor. Inhibition studies showed that 27.69 % of NH4+-N was removed through nitrogen removal pathways such as heterotrophic nitrification or direct conversion, and 20.55 % of TN was removed through aerobic denitrification. Microbial community analysis confirmed the presence of heterotrophic nitrifiers and aerobic denitrifiers. This study highlighted that the varied redox conditions offered by limited aeration would be beneficial for nitrogen removal, thereby reducing the energy usage and operating costs.

Enrichment of phosphate-accumulating organisms (PAOs) in a microfluidic model biofilm system by mimicking a typical aerobic granular sludge feast/famine regime

Wastewater treatment using aerobic granular sludge has gained increasing interest due to its advantages compared to conventional activated sludge. The technology allows simultaneous removal of organic carbon, nitrogen, and phosphorus in a single reactor system and is independent of space-intensive settling tanks. However, due to the microscale, an analysis of processes and microbial population along the radius of granules is challenging. Here, we introduce a model system for aerobic granular sludge on a small scale by using a machine-assisted microfluidic cultivation platform. With an implemented logic module that controls solenoid valves, we realized alternating oxic hunger and anoxic feeding phases for the biofilms growing within. Sampling during ongoing anoxic cultivation directly from the cultivation channel was achieved with a robotic sampling device. Analysis of the biofilms was conducted using optical coherence tomography, fluorescence in situ hybridization, and amplicon sequencing. Using this setup, it was possible to significantly enrich the percentage of polyphosphate-accumulating organisms (PAO) belonging to the family Rhodocyclaceae in the community compared to the starting inoculum. With the aid of this miniature model system, it is now possible to investigate the influence of a multitude of process parameters in a highly parallel way to understand and efficiently optimize aerobic granular sludge-based wastewater treatment systems.Key points• Development of a microfluidic model to study EBPR.• Feast-famine regime enriches polyphosphate-accumulating organisms (PAOs).• Microfluidics replace sequencing batch reactors for aerobic granular sludge research.

Simultaneous removal of organic carbon, nitrogen and sulfate, electricity generation and microbial community in anaerobic fluidized bed-microbial fuel cell

Simultaneous removal of organic carbon, nitrogen and sulfate, electricity generation and microbial community in anaerobic fluidized bed-microbial fuel cell

A novel reactor combining anammox and Fenton-like reactions for the simultaneous removal of organic carbon and nitrogen at different organic carbon to nitrogen ratios

A Fenton-like reaction and anaerobic ammonium oxidation (anammox) were combined to construct a novel process named FenTaMox for removing nitrogen (N) and organic carbon (measured as chemical oxidation demand (COD)). Two columns were packed with iron-manganese-sepiolite, a catalyst that uses hydrogen peroxide (H2O2) to catalyze Fenton-like reactions, and inoculated with marine anammox bacteria. During the start-up, marine anammox medium was fed into both columns to acclimate the marine anammox bacteria to iron-manganese-sepiolite. Batch experiments revealed that the marine anammox bacteria were not affected by 60 mgL−1 of H2O2. Next, medium containing glucose and H2O2 was fed into one column as the FenTaMox treatment, while medium containing glucose but no H2O2 was fed into the other column as the control. At a COD/N of 4, FenTaMox exhibited higher removal efficiencies of N and COD compared with that of the control, suggesting the application of FenTaMox for organic carbon- and N- removal.

Simultaneous removal of organic carbon and nitrogen pollutants in the Yangtze estuarine sediment: The role of heterotrophic nitrifiers

The Yangtze Estuary is one of the most eutrophic coastal areas in the world. The engagement of heterotrophic nitrification bacteria in the simultaneous removal of organic carbon and ammonium in the Yangtze estuarine sediment was investigated. The specific nitrification rate in the selective autotrophic nitrification inhibition treatment was about 25% of that in the control without autotrophic nitrification inhibition, suggesting that heterotrophic nitrification, in addition to autotrophic nitrification, was an important nitrification process in the sediment. The increase of heterotrophic nitrification can offset the decrease in autotrophic nitrification, which subsequently leads to the high tolerance of nitrification to the organic carbon. The number of heterotrophic nitrification bacteria was 7.1 × 107 MPN g−1 in sediment collected from Site 1 while that of autotrophic nitrification bacteria was 4.2 × 108 MPN g−1. The isolation of heterotrophic nitrification bacteria provides direct evidence of the engagement of heterotrophs in the nitrification of the Yangtze estuarine sediment. The results show that nitrification is catalyzed by both the autotrophs and the heterotrophs, indicating functional redundancy of nitrification in sediment. Since organic carbon usually coexists with ammonium, these findings indicate an alternative bioprocess for the simultaneous removal of organic carbon and ammonium in Yangtze estuarine sediment.

Performance of integrated anaerobic/aerobic sequencing batch reactor treating poultry slaughterhouse wastewater

The present study investigates the performance of a new configuration laboratory-scale bioreactor comprising of two regimes (anaerobic & aerobic) in one reactor with physical separation and it is known as integrated anaerobic/aerobic sequencing batch reactor (IAASBR). The IAASBR is designed for treating high-strength wastewater such as poultry slaughterhouse wastewater (PSW) along with the simultaneous removal of organic carbon and ammoniacal nitrogen (NH3-N). The IAASBR exhibits that the average removal efficiency of total COD (TCOD), soluble COD (SCOD), NH3-N, fat, oil & grease (FOG), and total suspended solids (TSS) were (97%±2%), (95%±3%), (98%±1.3%), (90%±11%), and (96%±3%) respectively. The laboratory comparison test revealed that IAASBR configuration has enhanced the sludge settle-ability for aerobic SBR more than the conventional SBR or settling tank. Furthermore, IAASBR could tolerate the shock loading occurrence, handle organic loading rate (OLR) up to 4.5kg(TCOD)m−3d−1 and produce a high-quality effluent complying with Malaysian standards of industrial’s effluents.

Polishing of Chemical Oxygen Demand (COD) Using Moving Bed Bio-Reactor

The pilot-scale experiment in moving bed biofilm reactor (MBBR) with a capacity of 433 L was carried out for this study with real life situations, it was decided that the complete research work must be done under as realistic conditions as possible,i.e.with real municipal wastewater, chemical free and with local commercially available products such as carriers for biofilm reactor. The reactor was start-up in 30/9/2013 up to date, Effluent from clarifier of STP used as influence of MBBR for polishing. MBBR is using continues down flow to polish effluent municipal wastewater from a faculty of new building engineering community in UKM to get the water free from main pollutant parameters, for reuse in the irrigation or discharge to the river. Laboratory experiments will conduct with different hydraulic retention time (HRT), filling ratio of plastic (Enviro Multi Media) in the MBBR about 5%. Aerobic reactors used the majority of the decaying organic material. An average removal rate of 41.75%, 32.85%, 24.80% and 35.77% of initial chemical oxygen demand (COD) were achieved under a HRT of 24hr, 12hr, 6hr and 2hr, respectively. The model simulated results showed good agreements with experimental results. The model could be employed in the design of a full-scale MBBR process for simultaneous removal of organic carbon from effluent STP.

Production of protein‐ and carbohydrate‐EPS in activated sludge reactors operated at different carbon to nitrogen ratios

AbstractBACKGROUNDThis study aimed to clarify how a variation in the carbon to nitrogen (C/N) ratio in influent wastewater affects the production and composition of extracellular polymeric substances (EPS) in activated sludge. In the literature such a comparative analysis is rarely presented, most studies on EPS focus on simultaneous organic carbon removal and nitrification whereas little attention is paid to the case of low organic load or separate‐stage nitrification.RESULTSAmong the very loosely bound, loosely bound and tightly bound EPS fractions, tightly bound EPS prevailed in semi‐continuously fed batch activated sludge reactors that were fed at a C/N ratio of 10, 5 and 0, respectively. The C/N ratio had no clear effect on total EPS production, however it changed the proportion of proteins and carbohydrates. In each sludge proteins constituted the dominant part of EPS, but the EPS of the nitrifying sludge (C/N = 0), had a definitely higher protein content. As evidenced by HPSEC fingerprints, in all EPS fractions most proteins had MWs ≤16 kDa. Depending on the C/N ratio in a reactor, high MW proteins in EPS shifted from tightly bound fractions to others.CONCLUSIONThe study is among the few that highlight how the protein and carbohydrate content in EPS changes at different C/N ratios. Since wastewater composition in a treatment system affects the chemical composition of EPS, each sludge might have different responses to uptake of xenobiotics such as metals. Further, this difference in composition might affect sludge settling, dewatering and membrane fouling. © 2014 Society of Chemical Industry

Kinetic Modeling for Simultaneous Organic Carbon Oxidation, Nitrification, and Denitrification of Abattoir Wastewater in Sequencing Batch Reactor

ABSTRACTA laboratory-scale study was conducted in a 20.0-L sequencing batch reactor (SBR) to explore the feasibility of simultaneous removal of organic carbon and nitrogen from abattoir wastewater. The reactor was operated under three different combinations of aerobic-anoxic sequence, viz., (4+4), (5+3), and (5+4) h of total react period, with influent soluble chemical oxygen demand (SCOD) and ammonia nitrogen (NH4+-N) level of 2200 ± 50 and 125 ± 5 mg L−1, respectively. In (5+4) h cycle, a maximum 90.27% of ammonia reduction corresponding to initial NH4+-N value of 122.25 mg L−1 and 91.36% of organic carbon removal corresponding to initial SCOD value of 2215.25 mg L−1 have been achieved, respectively. The biokinetic parameters such as yield coefficient (Y), endogenous decay constant (kd), and half-velocity constant (Ks) were also determined to improve the design and operation of package effluent treatment plants comprising SBR units. The specific denitrification rate (qDN) during anoxic condition was estimated as 6.135 mg N/g mixed liquor volatile suspended solid (MLVSS)·h on 4-h average contact period. The value of Y, kd and Ks for carbon oxidation and nitrification were found to be in the range of 0.6225–0.6952 mg VSS/mg SCOD, 0.0481–0.0588 day−1, and 306.56–320.51 mg L−1, and 0.2461–0.2541 mg VSS/mg NH4+-N, 0.0324–0.0565 day−1, and 38.28–50.08 mg L−1, respectively, for different combinations of react periods.

Treatment of Slaughter House Wastewater in a Sequencing Batch Reactor: Performance Evaluation and Biodegradation Kinetics

Slaughterhouse wastewater contains diluted blood, protein, fat, and suspended solids, as a result the organic and nutrient concentration in this wastewater is vary high and the residues are partially solubilized, leading to a highly contaminating effect in riverbeds and other water bodies if the same is let off untreated. The performance of a laboratory-scale Sequencing Batch Reactor (SBR) has been investigated in aerobic-anoxic sequential mode for simultaneous removal of organic carbon and nitrogen from slaughterhouse wastewater. The reactor was operated under three different variations of aerobic-anoxic sequence, namely, (4+4), (5+3), and (3+5) hr. of total react period with two different sets of influent soluble COD (SCOD) and ammonia nitrogen (NH4 +-N) level 1000 ± 50 mg/L, and 90 ± 10 mg/L, 1000 ± 50 mg/L and 180 ± 10 mg/L, respectively. It was observed that from 86 to 95% of SCOD removal is accomplished at the end of 8.0 hr of total react period. In case of (4+4) aerobic-anoxic operating cycle, a reasonable degree of nitrification 90.12 and 74.75% corresponding to initial NH4 +-N value of 96.58 and 176.85 mg/L, respectively, were achieved. The biokinetic coefficients (k, K s, Y, k d) were also determined for performance evaluation of SBR for scaling full-scale reactor in future operation.

Cascade bioreactor with submerged biofilm for aerobic treatment of Tunisian landfill leachate

A bioreactor cascade with a submerged biofilm is proposed to treat young landfill leachate of jbel chakir landfill site south west from capital Tunis, Tunisia. The prototype was run under different organic loading charges varying from 0.6 to 16.3kgTOCm−3day−1. Without initial pH adjustment total organic carbon (TOC) removal rate varied between 65% and 97%. The total reduction of COD reached 92% at a hydraulic retention time of 36h. However, the removal of total kjeldahl nitrogen for loading charges of 0.5kgNm−3day−1 reached 75%. The adjustment of pH to 7.5 improved nitrogen removal to a rate of 85% for loading charge of 1kgNm−3day−1. The main bacterial groups responsible for a simultaneous removal of organic carbon and nitrogen belonged to Bacillus, Actinomyces, Pseudomonas and Burkholderia genera. These selected isolates showed a great capacity of degradation at different leachate concentrations of total organic carbon.

Influence of organic loading on nitrogen removal in a partially aerated submerged filter

Influence of organic loading on simultaneous removal of organic carbon and nitrogen was investigated in a partially aerated submerged filter. This study indicates that high removal rates of organic carbon and nitrogen can be achieved in a single reactor. Organic loading had significant influence on nitrogen removal. Increase in COD loading promoted microanoxic conditions established within aerobic biofilms and facilitated denitrification occurring simultaneously with nitrification. This led to the nitrogen removal efficiencies increased from 27% to 77%. The results of this work are significant in developing compact biological system to treat wastewater with high concentrations of organics and nitrogen.

Performance study of the reduction of excess sludge and simultaneous removal of organic carbon and nitrogen by a combination of fluidized- and fixed-bed bioreactors with different structured macroporous carriers

Aiming for the reduction of excess sludge and the simultaneous removal of organic carbon and nitrogen, a new two-stage bioreactor system constructed by combining three-phase fluidized-bed (TFB) and sludge-reduction fixed-bed bioreactor (SFB) processes with different structured porous carriers was proposed. In this system, wastewater was first treated in the TFB bioreactor, in which the organic and nitrogenous compounds were simultaneously removed, and then the excess sludge produced in the TFB and residual organic substances flowed into the SFB for further degradation of suspended solids (SS) and nutrient removal. During a 470-day continuous operation, the average COD removal ratio reached about 95% at the influent COD of 500–600 mg/L. The removal ratio of T-N could reach up to 28–55% and was carried out through both microbial growth and simultaneous nitrification and denitrification (SND). The SS from TFB could be reduced in the following fixed-bed from 160 mg/L to 28 mg/L with two SFBs without the settling tank. Therefore, the simultaneous removal of organic carbon and nitrogen with an on-site reduction of excess sludge could be achieved in this two-stage bioreactor.

Natural organic matter (NOM) removal and structural changes in the bacterial community during artificial groundwater recharge with humic lake water

This study evaluated the removal of natural organic matter (NOM) and structural changes in the microbial community during infiltration of humic lake water at three artificial groundwater recharge (AGR) sites in Finland. The three sites were at waterworks in Hämeenlinna, Jyväskylä and Tuusula, sites A, B and C, respectively. Site A used groundwater recharge by both basin and sprinkling infiltration, site B used only sprinkling infiltration, and site C used only basin infiltration. Reductions of total organic carbon at sites A, B and C were 91%, 84% and 74%, respectively, in the winter, and 88%, 77% and 73%, respectively, in the summer. The Finnish national recommended value of 2 mg/l for TOC was achieved at all sites and the TOC of natural groundwater at site C was much lower, at 0.6 mg/l. Large molecular fractions of NOM were removed more efficiently than the smaller ones. Total amount of DAPI-stained cells decreased during infiltration at sites A, B and C in winter by 94%, 94% and 75% and in summer by 96%, 97% and 94%, respectively. Bacterial communities in raw waters and extracted groundwaters were diverse with changes occurring during infiltration, which was shown by DNA extraction followed by PCR of 16S rRNA genes and denaturing gradient gel electrophoresis (DGGE) fingerprinting. While the natural groundwater microbial community was diverse, it was different from that of the extracted groundwater in the AGR area. Simultaneous organic carbon removal and the decrease of bacterial counts during infiltration indicated biodegradation. In addition, the changing DGGE profiles during the process of infiltration, demonstrated that changing environmental conditions were reflected by changes in bacterial community composition.

Boosting nitrification by membrane-attached biofilm

Nitrification is a key step for reliable biological nitrogen removal. In order to enhance nitrification in the activated sludge (AS) process, membrane-attached biofilm (MAB) was incorporated in a conventional activated sludge tank. Simultaneous organic carbon removal and nitrification of the MAB incorporated activated sludge (AS + MAB) process was investigated with continuous wastewater treatment. The effluent TOC concentration of AS and the AS + MAB processes were about 6.3 mg/L and 7.9 mg/L, respectively. The TOC removal efficiency of both AS and AS + MAB were above 95% during the wastewater treatment, indicating excellent organic carbon removal performance in both processes. Little nitrification occurred in the AS process. On the contrary, successful nitrification was obtained with the AS + MAB process with nitrification efficiency of about 90%. The volumetric and surface nitrification rates were about 0.14 g/Ld and 6.5 g/m2d, respectively. The results clearly demonstrated that nitrification in the conventional AS process was boosted by MAB. Furthermore, the microfaunal population in the AS + MAB process was different from that in the AS process. The high concentration of rotifers in the AS + MAB process was expected to decrease the generation of excess sludge in the process.

A novel granular sludge sequencing batch reactor for removal of organic and nitrogen from wastewater

Microbial granules were developed at different substrate N/COD ratios in sequencing batch reactors (SBR). Results showed that heterotrophic, nitrifying, and denitrifying populations could peacefully co-exist in microbial granules, while increased substrate N/COD ratio led to significant shifts among three populations in granules. Enhanced activities of nitrifying and denitrifying populations were obtained in microbial granules developed at high substrate N/COD ratios, however, heterotrophic populations in granules tended to decrease with the increase of substrate N/COD ratio. It was found that dissolved oxygen (DO) concentration had a pronounced effect on the efficiency of denitrification by microbial granules, meanwhile the results also indicated that a certain mixing power would be provided to ensure mass transfer between liquid and granules during denitrification. It was demonstrated that complete organics and nitrogen removal can be achieved in single granule-based SBR with high efficiency and stable performance. This is the first study to show the capability of microbial granules in simultaneous removal of organic carbon and nitrogen from wastewater.

Inhibition of free ammonia to the formation of aerobic granules

This study investigated the inhibition of free ammonia to the development of aerobic granules for simultaneous organic carbon removal and nitrification in sequencing batch reactors. Five column sequencing batch reactors (SBRs) were operated at different N/COD ratios in the range of 5/100 to 30/100. Results showed that aerobic granules formed only when the free ammonia concentration were less than 23.5 mg l −1, and nitrification was completely inhibited at a free ammonia concentration greater than 10 mg l −1. It was found that the specific oxygen utilization rates of heterotrophic and nitrifying bacteria were reduced by a factor 5 and 2.5 as the free ammonia concentration increased from 2.5 to 39.6 mg N l −1. Free ammonia resulted in a significant decrease of cell hydrophobicity, and also repressed the production of cell polysaccharides. These would be responsible for the failure of aerobic granulation at high free ammonia concentrations. This study probably for the first time demonstrated that free ammonia could hinder the formation of aerobic granules through its inhibition to energy metabolism of microorganisms.

Reduction of Excess Sludge and Simultaneous Removal of Organic Carbon and Nitrogen by the Porous Carrier and Membrane Hybrid System

In a fluidized-bed porous carrier system, organic carbon and nitrogen in wastewater can be removed simultaneously. However, the excess sludge generated in the system has not been focused on. On the other hand, a membrane system can separate suspended solid from treated water and retain slowly growing microbes such as nitrifiers in the aeration tank. Porous carrier and membrane hybrid system with these respective advantages has been studied to enhance the nitrogen removal efficiency. In this study, the hybrid system was investigated to compare with a conventional carrier system in terms of the nitrogen removal rate from complex artificial wastewater (CAW) containing polypeptone as a nitrogen source. Moreover, the amounts of excess sludge generated in both systems were evaluated. Longer sludge retention time of the hybrid system was expected to enhance the microbial autolysis and lead to the reduction of the excess sludge. Consequently, the amount of excess sludge generated in the hybrid system was reduced to about one-fourth of that in the carrier system for about two months. In addition, a lot of slowly growing protozoa preyed on the microorganisms, which might have contributed to the reduction of excess sludge. The removal rates of organic carbon and nitrogen in the hybrid system were higher than in the carrier system, due to the highly concentrated microorganisms in the hybrid system. A batch operation revealed that the nitrogenous compounds of polypeptone in CAW were rapidly removed by assimilation, while urea in the artificial wastewater was mainly removed by nitrification. Consequently, total nitrogen concentration in CAW containing polypeptone decreased faster than in artificial wastewater containing urea. These results show that nitrogenous compounds in CAW are easy to be removed. The hybrid system is an efficient system to enhance the nitrogen removal and has a capability to reduce the excess sludge.

Augmentation of self-purification capacity of sewer pipe by immobilizing microbes on the pipe surface

For the development of a sewer pipe that removes dissolved organic carbon (DOC) and nitrogen, a rectangular channel with a fabricated porous ceramic bed was investigated. The experimental channel was 1 m long, 2.0×10 −2 m wide, and 2.5×10 −2 m deep, the total volume being 0.81 l. Blocks of the ceramic bed with 2.0×10 −2 m 2 total surface area and 5.0×10 −3 m thickness were installed along the channel bed for the immobilization of microorganisms. Synthetic wastewater was used as the model sewage. Removal of organic carbon and nitrogen was carried out with or without aeration. Dissolved oxygen (DO) and pH microelectrodes were employed to analyze structure of the biofilm, which played an important role in the removal of both organic carbon and nitrogen. The results give evidence that the combination of aeration and biofilm development enhanced the simultaneous removal of organic carbon and nitrogen. Microelectrode study revealed that the biofilm was rough and heterogeneous in both vertical and horizontal directions and had an average thickness of 2.5–5 mm. The biofilm, consisting of an aerobic/anaerobic layer, was suggested to be responsible for the nitrification/denitrification process, while the aeration accelerated the removal of total organic carbon (TOC), NH 4 or NO 2 from the model sewage. Sequential nitrification/denitrification proceeded in the biofilm even when aeration was carried out. This study suggests that the immobilization of microbes inside the sewer pipe may be effective for the simultaneous removal of organic carbon and nitrogen in the sewage line.