Influent COD Concentration Research Articles

Estudio cinético del proceso de digestión anaerobia de aguas de lavado de aceitunas de almazara en reactores de mezcla completa con microorganismos inmovilizados

A kinetic study of the continuous anaerobic digestion process of wastewaters from the washing of olives prior to the oil production process was carried out in a completely mixed reactor with sepiolite immobilised biomass at 35° C. Four influent COD concentrations, 4,5, 3,5, 2,5 y 1,5 g COD/I were used as substrate operating for a hydraulic retention time range of 4,5 to 1,25 days. The Michaelis-Menten model has been applied, obtaining the values of the maximum substrate utilization rate, k ( (g COD/g VSS day), and the kinetic constant of the process, K s (g COD/I), for each influent substrate concentration studied. The values of these parameters significantly decreased with decreasing concentration of influent wastewater, showing the highest values for the greatest influent substrate concentration used as feed. The microbial yield coefficient, Y x , and sludge decay rate coefficient, k d , were also determined to be 0,14 g VSS/g COD and 0,003 days -1 respectively.

Performance of an Internal Circulating Three-Phase Fluidized Bed Bioreactor in Treating Petrochemical Wastewater

A 4.75 m3 volume pilot internal circulating three-phase fluidized bed bioreactor (ICTFBB) was developed to treat petrochemical wastewater with ceramic particles as biocarriers. In situ experimental results showed that: due to its higher content of extracellular polymer and filamentous microbes, collapsed biofilm was better than activated sludge as inoculum for new biofilm to build up and for the ICTFBB to start up. When influent total COD, oil, phenol, NH4-N and PO4-P concentrations were in the range of 353–1911 mg l−1, 11.6–55.7 mg l−1, 1.57–48.7 mg l−1, 10.1–53.5 mg l−1 and 2.3–5.4 mg l−1 respectively, average removal efficiencies of them were 75.9%, 75.3%, 92.8%, 40% and 87.2%, respectively. Average total COD removal rates were in the range of 6.6–10.4 kgCOD m−3.d−1, much higher than that of the control, the conventional activated sludge reactor, 1.28–2.5 kgCOD m−3d−1. Oxygen utilization efficiency was high as 14–22% in ICTFBB, higher than that of the control, 6–10%. Air supply was much lower in the ICTFBB. In addition, the ICTFBB had higher resistance to COD and phenol shock and ran more stable than the control.

Synthetic dairy wastewater treatment using cross flow medium trickling filter

The treatment of synthetic dairy wastewater was carried out using cross flow medium trickling filter of specific surface area 243 m2/m3. The operating variables in this study were hydraulic and organic loading rates. The hydraulic loadings employed in this study were 5, 9, 13 and 17 m3/m2.d for the influent COD concentrations of 427 to 1384 mg/l. It was observed that the relationship between organic removal rate and organic loading rate showed two regions of linear behaviour with the point of inflection at an organic loading rate of 26 g COD/m2.d. Kornegay model was used to evaluate the kinetic coefficients for the system. The results were found to be satisfactory.

Treatment of palm oil mill effluent (POME) with the membrane anaerobic system (MAS)

One of the major difficulties in anaerobic wastewater treatment processes is the need to retain a sufficient quantity of active biomass in the anaerobic reactor. The use of membranes to achieve external solid/liquid phase separation will result in the retention of the biomass at the surface of the membranes. In this study, the Membrane Anaerobic System (MAS) was used to treat industrial wastewater from a palm oil mill. The MAS was subjected to increasing organic loading rates (OLR) and a total of six steady states were attained. The first steady state influent COD concentration was 39,910 mg/l increasing to the final or sixth steady state COD concentration of 68,310 mg/1. The efficiency of COD removal was between 91.7 to 94.2 percent with an average HRT of 3.03 days. The maximum OLR applied during the sixth steady state was 21.7 kgCOD/m3/d. The reactor mixed liquor suspended solids (MLSS) was between 50,000 to 57,000 mg/1 while the percentage of the mixed liquor volatile suspended solids (MLVSS) was between 74 to 82 percent. A crossflow ultraftration (UF) module was used to filter the final effluent and simultaneously retain biomass in the anaerobic reactor. A clear final effluent was produced but membrane flux rate deterioration was observed due to membrane fouling. Membrane fouling could be minimised with faster crossflow feed velocities and regular membrane flushing.

Effect of chloride and condensable tannin in anaerobic degradation of tannery wastewaters

Toxic effect due to chloride and condensable tannin on anaerobic digestion of vegetable tanning wastewater was investigated at different hydraulic retention times viz 24, 48 and 60 hr respectively. The toxicity to anaerobic contact filter was observed at a chloride concentration of 4500 mg/l and tannin concentration of 790 mg/l respectively under synergistic condition. In the case of constant influent tannin concentration of 600 mg/l, the toxicity due to chloride on anaerobic contact filter was observed at 5500 mg/l. The COD removal percent ranged from 50% to 79% at 48 hr and 67% to 91% at 60 hr HRT respectively. In the case of constant influent chloride concentration of 4000 mg/l and at an increasing influent COD concentration, the toxicity due to tannin on anaerobic contact filter was observed at 1180 mg/l. The COD removal percent ranged from 64% to 89% at 48 hr and 78% to 96% at 60 hr HRT respectively. The results showed that at least 60 hr HRT would be desirable to have good COD removal percent.

Influencia de la velocidad de carga orgánica sobre el proceso de digestión anaerobia de aguas de lavado de aceitunas de almazara en reactores de lecho fluidizado

A study of the anaerobic digestion process of wastewaters from the washing of olives prior to the oil production process was carried out in a fluidized bed reactor with sepiolite immobilised biomass at 35°G. The bioreactor worked satisfactorily using Influent COD concentrations of 4.5,3.5,2.5 and 1.5 g COD/I for a hydraulic retention time (HRT) range of 4.5 to 1,25 days. COD removal efficiencies in the range 50-90% were achieved in the reactor, when evaluated at organic loading rates of between 0.46 and 2.25 g COD/I day using the highest influent substrate concentration (S o = 4.5 g COD/I). COD and volatile fatty acid (VFA) concentration were Increased In parallel with the increase of organic loading rate in the reactor, VFA concentration showing a maximum value of 1.55 g acetic acid/I at the most unfavourable case studied (S o = 4,5 g COD/I and HRT = 1.25 days). The increase in effluent VFA concentrations was always counteracted by the high alkalinity values (3440-4670 mg CaCO 3 /l) which brought about the high stability of the process and values of the alkalinity/VFA ratio lower than 0.3-0.5, except for the above-mentioned case, limit value over which the anaerobic process is destabilized. The yield coefficient of methane production was 0.281 methane STP/g COD removed.

Modeling of enhanced biological phosphorus removal in a sequencing batch biofilm reactor

A biofilm system operated for enhanced biological phosphorus removal is evaluated using a mathematical model. The influence of the influent COD concentration and the biofilm thickness are investigated. In an activated sludge system increasing the influent COD will result in a decrease of the effluent phosphorus concentration. However, in a biofilm system above a certain influent COD concentration not all COD supplied in the influent can be taken up during the anaerobic period. Other heterotrophic bacteria will then dominate the biofilm resulting in an increase of the effluent phosphorus concentration. A larger biofilm thickness will result in an increase of the total mass of polyphosphate-accumulating organisms in the system. However, it is shown that a larger biofilm thickness results in higher effluent phosphorus concentrations. The mathematical model presented is based on the IAWQ Model No. 2 modified for the biofilm system. Mass transport in the biofilm is modeled one-dimensionally. Removal of biomass through backwashing and, thus, removal of phosphorus, is included in the mathematical model. Simulations were used to explain experimental observations.

Modeling of enhanced biological phosphorus removal in a sequencing batch biofilm reactor

A biofilm system operated for enhanced biological phosphorus removal is evaluated using a mathematical model. The influence of the influent COD concentration and the biofilm thickness are investigated. In an activated sludge system increasing the influent COD will result in a decrease of the effluent phosphorus concentration. However, in a biofilm system above a certain influent COD concentration not all COD supplied in the influent can be taken up during the anaerobic period. Other heterotrophic bacteria will then dominate the biofilm resulting in an increase of the effluent phosphorus concentration. A larger biofilm thickness will result in an increase of the total mass of polyphosphate-accumulating organisms in the system. However, it is shown that a larger biofilm thickness results in higher effluent phosphorus concentrations. The mathematical model presented is based on the IAWQ Model No. 2 modified for the biofilm system. Mass transport in the biofilm is modeled one-dimensionally. Removal of biomass through backwashing and, thus, removal of phosphorus, is included in the mathematical model. Simulations were used to explain experimental observations.

The anaerobic treatment of low strength wastewaters in UASB and EGSB reactors

The application of the UASB and EGSB reactors for the treatment of low strength wastewaters was investigated. The effect of dissolved oxygen on the methanogenic activity of granular sludges, the low substrate levels inside reactors and lower temperatures on the treatment performance were evaluated. The results showed that methanogens located in granular sludge have a high tolerance to oxygen. The concentration to cause 50% inhibition to methanogenic activity was between 7% and 41% oxygen in the head space of flasks, corresponding to 0.05 mg/l and 6 mg/l of DO prevailing in the media, respectively. The feasibility of UASB and EGSB reactors at 30°C was demonstrated. In UASB reactors, COD removal efficiencies exceeded 95% at organic loading rates up to 6.8 g COD/l.d and influent COD concentrations ranging from 422 to 722 mg/l, during the treatment of ethanol substrate. In EGSB reactors, efficiencies were above 80% at OLRs up to 12 g COD/l.d with COD as low as 100 to 200 mg/l. The studies confirmed that in practice DO does not constitute any detrimental effect on the reactor treatment performance. Lowering the temperature down to 15°C in EGSB reactors also showed that the potentials of anaerobic technology can be further explored in the treatment of dilute wastewaters.

A Comparison of Different Support Materials in Anaerobic Fluidized Bed Reactors for the Treatment of Vinasse

Three identical anaerobic fluidized bed reactors containing different biomass support media were fed a distillery wastewater at various hydraulic retention times and COD loadings. The support media used were sepiolite, pumice stone and sand; particle diameter was around 0.5 mm in all cases. Start-up of the reactors was achieved within 63 days using a regime that included stepped increases in influent COD concentration and substitution of methanol for part of the wastewater COD. No significant differences in performance between reactors were observed during this period. Six different steady states at hydraulic retention times between 0.5 and 2.48 days were studied. Results obtained at these steady states showed similar performances in all three reactors except at HRT of 0.5 days, when the reactors containing sepiolite and pumice stone achieved better COD removal efficiencies and higher methane yields than the sand-containing reactor. It was concluded that sepiolite and pumice stone would be excellent solid supports in biological fluidized bed processes and have a lower energy consumption than the one demanded when using a sand support.

Influence of COD/NH3–N ratio on organic removal and nitrification using a modified RBC

Synthetic wastewaters were prepared with different influent concentrations of ammonia nitrogen (NH3–N) and COD and the treatment studies were conducted using a rotating biological contactor (RBC). If organic removal and nitrification can be simultaneously effected in one process, it will be an ideal solution to water pollution control. The RBC used in the present study was a four stage laboratory model and the discs were modified by attaching porous netlon sheets to enhance biofilm area. The COD loads (S0) used were about 1000 and 1500 mg/l whereas NH3–N concentrations used were in the range of 20 to 185 mg/l. Hydraulic load (q) of 0.03 m3 . m-2 . d-1 and ammonia nitrogen loadings in the range of 0.66 to 5.5 g NH3–N . m-2 . d-1 were used. The RBC was operated at two different rotating speeds of 6 and 12 rpm. The results showed that the nitrification and percentage of COD removal were not affected up to the value of the COD/NH3–N in the range from 47 to 23 at w=6 rpm and for an average influent COD of 1003 mg/l. Beyond that range only the nitrification rate decreased much whereas the percentage of COD removal was not affected. Similarly, at an influent COD load of 1557 mg/l, the nitrification and percentage COD removal were not affected for the value of the COD/NH3–N in the range from 44 to 23 but beyond that range only the nitrification rate decreased while the percentage of COD removal was approximately constant and still high. A correlation plot between the NH3–N removed and NH3–N applied was presented at a rotating speed of 6 rpm and it was found that the nitrification rate of 3.93 g NH3–N . m-2 . d-1 was achieved at ammonia loading of 5.55 g NH3–N . m-2 . d-1. Also the results at w=12 rpm showed improvement of nitrification rate over those at 6 rpm.

Effect of toxic substances in anaerobic treatment of tannery wastewaters

Studies were carried out in the treatment of tannery wastewater using upflow anaerobic contact filter (reactor) and on the role of toxic substances viz tannin, sulphide, chromium (3+) in inhibiting the performance of the reactor. The influent COD concentration was varied in the range of 1500 to 16500 mg/l, at different hydraulic retention times viz 36,48,60 hr. The limiting concentrations of toxicity for the three substances viz tannin, sulphide, chromium (3+) were identified in terms of the performance of the reactor viz COD removal percent, biogas production etc. Toxic limits of the above mentioned substances were further estimated in batch process (in vials) to supplement the evidence. In anaerobic contact filter tannin beyond 914 mg/l inhibited the performance, whereas sulphide concentration even upto 180 mg/l and chromium (3+) concentration even upto 140 mg/l did not affect the reactor performance. In batch process tannin above 77 wt.% affected the anaerobic microbial growth. Hydrolysable tannin was present in these tannery wastewaters.

The anaerobic treatment of low strength wastewaters in UASB and EGSB reactors

The application of the UASB and EGSB reactors for the treatment of low strength wastewaters was investigated. The effect of dissolved oxygen on the methanogenic activity of granular sludges, the low substrate levels inside reactors and lower temperatures on the treatment performance were evaluated. The results showed that methanogens located in granular sludge have a high tolerance to oxygen. The concentration to cause 50% inhibition to methanogenic activity was between 7% and 41% oxygen in the head space of flasks, corresponding to 0.05 mg/l and 6 mg/l of DO prevailing in the media, respectively. The feasibility of UASB and EGSB reactors at 30°C was demonstrated. In UASB reactors, COD removal efficiencies exceeded 95% at organic loading rates up to 6.8 g COD/l.d and influent COD concentrations ranging from 422 to 722 mg/l, during the treatment of ethanol substrate. In EGSB reactors, efficiencies were above 80% at OLRs up to 12 g COD/l.d with COD as low as 100 to 200 mg/l. The studies confirmed that in practice DO does not constitute any detrimental effect on the reactor treatment performance. Lowering the temperature down to 15°C in EGSB reactors also showed that the potentials of anaerobic technology can be further explored in the treatment of dilute wastewaters.

Treatment of recycled wastewaters from fishmeal factory by an anaerobic filter

Fishmeal industries processes produce effluents with high load organic matter. These effluents, after recycling and physical-chemical pretreatment, have a high organic content (5-6 g COD/l), proteins (3-5 g/l), salinity close to sea water, sodium chloride (30 g/l) and sulphate (1-3.3 g/l). An anaerobic filter was used for the treatment of this wastewater, with marine sediment as anaerobic inoculum. Anaerobic filter removed up to 70% of the influent COD concentrations at organic loading rates (OLR) of 9.5 and 14.3 (g/l d) and sulphate up to 80% at OLR of 7.1 and 14.3 (g/l d) whereas the pH ranged between 7.0 and 7.5. These results show that anaerobic filter systems are applicable to recycled wastewaters from fishmeal.

Biological nitrification kinetics in a fixed-film reactor

The kinetic parameters for combined carbon/nitrogen removal in a four-stage aerated submerged fixed-film (ASFF) bio-reactor of 50 l volume were evaluated using a synthetic wastewater at 20°C. Influent COD concentrations were in the range of 0·057-1·8 g COD l −1, and influent NH 3-N concentrations were in the range of 0·0152-0·48 g NH 3-N l −1 with hydraulic loading ranging from 0·028 to 0·112 m 3 m −2 day −1. Good nitrification was achieved even when high mass loadings were applied. The substrate (COD or ammonia) removal in the reactor was described by a substrate-limiting phenomenon (reaction or mass transport). Substrate-removal rate followed Monod kinetics in the first stage of the reactor but was better described by first-order kinetics in the second to the fourth stages as the substrate concentration became much lower. The order of the reaction was apparently a function of the hydraulic loading, indicating the influence of mass transfer on the ‘apparent’ order of the reaction.

Microbiology of activated sludge treating wastewater containing Ni(II) and Cr(VI)

The species of microorganisms dominating a laboratory-scale once-through activated sludge unit treating simulated wastewater with different influent strengths (650 and 1300 mgl−1 COD) and containing 5 to 10 mgl−1 Ni(II) and 1 to 50 mgl−1 Cr(VI) were identified by standard biochemical tests. Within this framework, combinations of metals and influent COD concentrations were tried. Organisms, namely Proteus rettgeri, Acinetobacter sp., Flavobacterium lutescens, Bacillus cereus var. albolactis, Klebsiella sp., Arthrobacter simplex, and Pseudomonas mendocina, were identified at different stages of the experiments.

A model for predicting nitrous oxide production during denitrification in activated sludge

To examine the importance of certain conditions on the production of nitrous oxide during denitrifications batch experiments with activated sludge were conducted. With the obtained parameters and a Monod kinetics based model the nitrous oxide concentrations in a CSRT were calculated. The influence of temperature, pH, nitrate influent concentration, readily biodegradable COD influent concentration, H2S and oxygen inhibitor concentrations are discussed. The presented model helps in understanding some previously described phenomena of nitrous oxide production in wastewater treatment plants.

Performance evaluation of an anaerobic hybrid digester treating palm oil mill effluent

Abstract A high‐strength palm oil mill effluent was treated using a hybrid anaerobic digester, in which the bottom two‐thirds were occupied by a sludge blanket and the upper one‐third by submerged PVC rings, under mesophilic conditions. The influent COD concentration varied considerably (11.6–65.0 g/1). The digester was subjected to quantitative increases in organic loading rate (OLR) from 3.3 to 18.6 kg COD/m3 day at a set hydraulic retention time (HRT) of 3.5 days. The data showed that the anaerobic digestion process is feasible for the treatment of, and methane generation from, palm oil mill effluent without pretreatment. A COD removal efficiency and methane yield of 92.3% and 0.335 m3/kg CODremoved, respectively, could be achieved at an OLR of 16.2 kg COD/m3 day. The data also showed that the hybrid digester could be maintained at a HRT of 3.5 days with an OLR of 18.6 kg COD/m3 day. This rate is significantly faster than the rates achieved in previously reported studies. Decreasing digester efficiency...

Microbiology of activated sludge treating wastewater containing Ni(II) and Cr(VI)

The species of microorganisms dominating a laboratory-scale once-through activated sludge unit treating simulated wastewater with different influent strengths (650 and 1300 mgl−1 COD) and containing 5 to 10 mgl−1 Ni(II) and 1 to 50 mgl−1 Cr(VI) were identified by standard biochemical tests. Within this framework, combinations of metals and influent COD concentrations were tried. Organisms, namely Proteus rettgeri, Acinetobacter sp., Flavobacterium lutescens. Bacillus cereus var. albolactis, Klebsiella sp., Arthrobacter simplex, and Pseudomonas mendocina, were identified at different stages of the experiments.

A model for predicting nitrous oxide production during denitrification in activated sludge

To examine the importance of certain conditions on the production of nitrous oxide during denitrifications batch experiments with activated sludge were conducted. With the obtained parameters and a Monod kinetics based model the nitrous oxide concentrations in a CSRT were calculated. The influence of temperature, pH, nitrate influent concentration, readily biodegradable COD influent concentration, H2S and oxygen inhibitor concentrations are discussed. The presented model helps in understanding some previously described phenomena of nitrous oxide production in wastewater treatment plants.