Biological nitrogen removal of high-strength ammonium industrial wastewater with two-sludge system

Monitoring the removal of nitrogen by applying a nitrification-denitrification process in a Sequencing Batch Reactor (SBR)

In this study the evaluation of nitrogen removal in wastewater from a meat products processing company was performed, using a Sequencing Batch Reactor (SBR) at pilot scale. The phases of the SBR operation were: filling, reaction (aeration and intermittent anoxia), sedimentation and discharge. In each of these phases analyses of ammonium (NH(4)(+)), nitrite (NO(2)(-)), nitrate (NO(3)(-)), pH and dissolved oxygen (DO) were carried out to monitor the process of nitrification-denitrification. The results showed that stage IV had the best performance (2.49 g COD(F)/Ld and 1.02 g NH(4)(+)-N/Ld) with a NH(4)(+)-N removal of 71%. The transformation of much of the NH(4)(+)-N to gaseous nitrogen was confirmed, with the concentration of NO(2)(-)-N and NO(3)(-)-N increasing during the reaction phase but decreasing in the effluent due to its transformation to gaseous nitrogen.

Limitations encountered for the treatment of a low C:N waste using a modified membrane-aerated biofilm reactor

A modified membrane-aerated biofilm reactor (mMABR) that combined oxygen permeable membranes and inert attachment media to support both nitrification and denitrification was used to treat a carbon-limited (COD:N = 1.8) and ammonium-rich (NH4+ = 650 g-N/m3) space habitation waste stream. An eight-fold increase in intramembrane air pressure did not affect process performance; however, for an air pressure of 11 kPa (gauge), lower and upper hydraulic loading limits for the mMABR were identified at 30 g-N/m3 x d and 123 g-N/m3 x d, respectively. Oxygen limitation occurred at the highest loading rate and alkalinity limitation occurred at the lowest loading rate. Partial nitrification was noted at both limitations. Additionally, increased recirculation ratios were shown to decrease denitrification efficiency. Mean carbon and nitrogen removal rates were as high as 75.3 g-C/m3 x d (0.26 g-C/m2d) and 63.8 g-N/m3 x d (0.22 g-N/m2 x d), respectively. The mMABR achieved maximal nitrification and denitrification performance given the stoichiometric nature of the waste.

Feasibility of focused-pulsed treated waste activated sludge as a supplemental electron donor for denitrification

We evaluated the feasibility of using waste activated sludge (WAS) from a wastewater treatment plant as an internal electron donor to fuel denitrification, by increasing its bioavailability with Focused-Pulsed (FP) technology. The focused-pulsed treatment of WAS (producing FP-WAS) increased the semi-soluble chemical oxygen demand (SSCOD) by 26 times compared with the control WAS. The maximum denitrification rate of FP-WAS (0.25 g nitrate-nitrogen [NO3- -N]/g volatile suspended solids [VSS] x d) was greater than for untreated WAS (0.05 g NO3- -N/g VSS x d) and methanol (0.15 NO3- -N/g VSS x d). Centrifuging out the larger suspended solids created FP-centrate, which had a rate (0.14 g NO3- -N/g VSS x d) comparable with that of methanol. Thus, FP treatment of WAS created SSCOD, which was an internal electron donor that was able to drive denitrification at a rate similar to or greater than methanol. One trade-off of using FP-WAS for denitrification is an increase in total Kjeldahl nitrogen (TKN) loading. While FP-WAS achieved the lowest total nitrogen and NO3- -N concentrations in the batch denitrification test, its final ammonia-nitrogen (NH3-N) concentration was the highest, as a result of the release of organic nitrogen from the FP-treated biomass; FP-centrate had less release of total soluble nitrogen. While the return of total nitrogen (TN) is small compared with the SSCOD, the effects of the added nitrogen loading need to be considered.

Nitrification of ammonium-rich sanitary landfill leachate

The nitrification of ammonium-rich wastewater is considered challenging due to the substrate inhibition particularly in the form of free ammonia (FA) and free nitrous acid (FNA) in ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). The feasibility of the nitrifying activated sludge system to completely nitrify synthetic stabilized landfill leachate with N-NH(4)(+) concentration of 1452mg/L was tested in this study. The process started with 0.4kg N-NH(4)(+)/m(3)/day of nitrogen loading rate (NLR) in a fed-batch mode to avoid any accumulation of the FA and FNA in the system followed by increasing the nitrogen loading rate (NLR) gradually. Complete nitrification was achieved with a very high ammonium removal percentage (approximately 100%). The maximum specific and volumetric nitrification rate obtained were 0.49g N-NH(4)(+)/g VSS/day and 3.0kg N-NH(4)(+)/m(3)/day, respectively which were higher than those reported previously for ammonium-rich removal using activated sludge system. The nitrifying sludge exhibited good settling characteristics of up to 36mL/g VSS and a long SRT of more than 53 days which contributed to the success of the nitrification process. The coexistence and syntrophic association of the AOB and NOB was observed by using Fluorescence in situ hybridization (FISH) technique which supported the results on complete nitrification obtained in the system. These findings would be of prominent importance for further treatment of actual sanitary landfill leachate.

Nitrogen removal from landfill leachate via ex situ nitrification and sequential in situ denitrification

Ex situ nitrification and sequential in situ denitrification represents a novel approach to nitrogen management at landfills. Simultaneous ammonia and organics removal was achieved in a continuous stirred tank reactor (CSTR). The results showed that the maximum nitrogen loading rate (NLR) and the maximum organic loading rate (OLR) was 0.65gNl(-1)d(-1) and 3.84gCODl(-1)d(-1), respectively. The ammonia and chemical oxygen demand (COD) removal was over 99% and 57%, respectively. In the run of the CSTR, free ammonia (FA) inhibition and low dissolved oxygen (DO) were found to be key factors affecting nitrite accumulation. In situ denitrification was studied in a municipal solid waste (MSW) column by recalculating nitrified leachate from CSTR. The decomposition of MSW was accelerated by the recirculation of nitrified leachate. Complete reduction of total oxidized nitrogen (TON) was obtained with maximum TON loading of 28.6gNt(-1)TSd(-1) and denitrification was the main reaction responsible. Additionally, methanogenesis inhibition was observed while TON loading was over 11.4gNt(-1)TSd(-1) and the inhibition was enhanced with the increase of TON loading.

Phragmites australis and Typha orientalis in removal of pollutant in Taihu Lake, China

Two plant populations of Phragmites australis and Typha orientalis grown in gravel and sediment substrate were studied to assess their capabilities for purifying polluted water in Taihu Lake, China. The substrate displayed most significant effects on the suspended matter (P < 0.01), with the reduction of 76%-87% and 52%-63% for P. australis, and 83%-86% and 45%-62% for T. orientalis in gravel substrate and sediment substrate, respectively. Both species and substrates significantly decreased the N and P concentrations of water body (P < 0.01). P. australis showed higher total N and P concentrations in tissues than T. orientalis and had a greater potential to remove nutrients from the lake. Phosphate was easily to concentrate in the belowground tissues, while nitrate concentration was higher in leaf and stalk. Therefore, harvesting the aboveground tissues could take most of nitrate out of the sediment. The saturate photosynthetic rate (Asat) of P. australis was higher than that of T. orientalis when grown in sediment substrate. But instance water-use-efficiency (WUEi) (A/E) and intrinsic water use efficiency (A/gs) showed the maximum values of two species grown in river water. With significant difference in gs, however, intercellular CO2 concentration (Ci) had no obvious difference in two species which indicated that high Asat value of P. australis might result from the increased carboxylation capacity of the mesophyll, because of the central role of N in photosynthetic enzymes. Our findings suggest that the plants could absorb most of nitrogen in polluted water, while gravel displayed a high capacity for absorbing the suspended matters and phosphate salts. Therefore, biological and physiological pathways for pollutant removal should be integrated.

Application of the activated sludge model for nitrogen to elevated nitrogen conditions

The Activated Sludge Model for Nitrogen (ASMN) was evaluated by conducting simulations under both steady-state and dynamic conditions using a wastewater containing high concentrations of chemical oxygen demand (COD) and nitrogen, and an inhibitor of ammonia-oxidizing bacteria. The adopted wastewater characteristics were based on data from several industrial wastewater treatment facilities. The simulations were performed at a variety of temperatures, solids retention times, dissolved oxygen concentrations, pH values, and salt concentrations. The nitrification operating window was defined, and denitrification performance was characterized. The pH and temperature were found to be the most important variables affecting nitrification performance under upset or startup conditions, with lower pH values allowing better performance at higher temperatures for the high-nitrogen wastewater used in the simulations. Emissions of nitric oxide and nitrous oxide were higher than generally thought to occur and were directly linked to depletion of the electron donor in the anoxic reactor. The findings concerning pH, temperature, and gaseous emissions were all consistent with the known growth characteristics of nitrifying and denitrifying bacteria. Parameter and process variable sensitivity studies were performed, and guidelines for improved biological nitrogen removal were developed.

Partial nutrient removal under insufficient organic carbon from digested swine wastewater in sequencing batch biofilm reactor

The objective of this study was to investigate the possibility of using a biofilm process for partial nutrient removal from digested swine wastewater containing low ratios of chemical oxygen demand (COD) to nitrogen and phosphorus; on average, 1.6 g COD g(-1) N and 7 g COD g(-1) P. We used a laboratory-scale sequencing batch biofilm reactor with alternating conditions of 4 hours anaerobic/ 12 hours aerobic, and a hydraulic retention time of 16 hours. Although the concentration of dissolved oxygen under aerobic conditions was > 2.5 mg L(-1), the efficiency of denitrification was up to 85% of the theoretical maximum at the available influent COD, with an ammonia removal rate of 0.73 g N m(-2) d(-1) and without the accumulation of nitrite or nitrate. Activity tests showed that the biomass from the reactor consisted of denitrifying polyphosphate accumulating organisms (DNPAO) that can use nitrite as an electron acceptor. The organic carbon in the digested swine wastewater was utilized very effectively through the denitrifying phosphorus uptake process, as implied by the low utilization ratios of COD to nitrogen, 4.2 g COD g(-1) N, and phosphorus, 14 g COD g(-1) P. A COD value as low as 50 mg L(-1) and an increased ratio of nitrogen to phosphorus from 4:1 to 6:1 in the effluent, which is more suitable for use as a liquid fertilizer, were achieved through the processes of nitrification and denitrifying phosphorus uptake in the sequencing batch biofilm reactor.

Experimental validation of a model describing the cycle of nitrogen in a step sludge recirculation activated sludge system with denitrification

In this paper, a model describing the cycle of nitrogen in a Step Sludge Recirculation (SSR) reactor, was developed. The SSR reactor is a multistage, continuous stirred tank reactor where the recycled biomass is distributed over all stages. The SSR system provides a uniform treatment of the wastewater and high purification efficiency for both carbon and nitrogen removal. The objective of this work was to develop a mathematical model of the SSR system, based on the analysis of various parameters that are present in the system. The simplified form of the IWA-ASM model was adapted to include the carbon removal, nitrification and denitrification processes. For model validation, a SSR pilot plant fed with synthetic wastewater was operated for approximately four months. The experimental results show that the SSR system seems to be appropriate to attain maximum TOC and nitrogen removal with minimum sludge production. The proposed model seems to be capable of expressing the behavior of carbon removal, nitrification, denitrification and various microorganism species in a SSR configuration of a nitrogen cycle. When the experimental results were compared with those estimated by the proposed model, the model predictions matched well with the experimental results.

Synergism effects of phenol-degrading yeast and ammonia-oxidizing bacteria for nitrification in coke wastewater of Esfahan Steel Company

Ammonia-oxidizing bacteria and phenol-degrading yeast were isolated in order to study the synergism effects of phenol-degrading yeast and ammonia-oxidizing bacteria for enhancing the nitrification in coke wastewater from the Isfahan Steel Company. The influent and effluent samples with approximately 600-1200 mg L(-1) ammonium and 550-2350 mg L(-1) phenol were collected aseptically in sterile flasks. The biodegradation of phenol and nitrification were studied with different treatments. The results showed that addition of Na2CO3 and autotrophic bacteria to wastewater increased the ammonium removal by 100%. Furthermore, the synergism effects of phenol-degrader yeast and autotrophic bacteria reduced the time for ammonium removal.

Ammonium exchange in aqueous solution using Chinese natural clinoptilolite and modified zeolite

In this study, the Chinese natural clinoptilolite (sample 1) was fused with sodium hydroxide prior to hydrothermal reaction, and it was transformed to modified zeolite Na-Y (sample 2). The uptake of ammonium ion from aqueous solutions in the concentration range 50-250 mg NH(4)(+)/l on to the two samples was compared and the equilibrium isotherms have been got. The influence of other cations present in water upon the ammonia uptake was also determined. The cations studied were potassium, calcium and magnesium. In all cases the anionic counterion present was chloride. The results showed that sample 2 exhibited much higher uptake capacity compared with sample 1. At the initial concentration of 250 mg NH(4)(+)/l, the ammonium ion uptake value of sample 2 was 19.29 mg NH(4)(+)g(-1) adsorbent, while sample 1 was only 10.49 mg NH(4)(+)g(-1) adsorbent. For the natural clinoptilolite, the effect of the metal ions suggested an order of preference K(+)>Ca(2+)>Mg(2+). These contrasted with the modified zeolite, where the order appeared to be Mg(2+)>Ca(2+)>K(+).

Inorganic carbon limitations on nitrification: experimental assessment and modelling

Nitrification is a two-step process that involves two different biomass populations: ammonia oxidising biomass (AOB) and nitrite oxidising biomass (NOB). Both populations are autotrophic (i.e. their carbon source is inorganic). Therefore, a deficit of this substrate should result in a decrease of the process rate. Recent technology advances such as the SHARON process have brought new scenarios in biological nitrogen removal where these limitations should be considered. Hence, this work examines the inorganic carbon limitation using respirometric and titrimetric techniques. For this aim, the nitrification rate was measured at different total inorganic carbon (TIC) concentrations. The experimental results obtained show that AOB was limited at TIC concentrations lower than 3mmol CL(-1). At the same time, no carbon source limitation for NOB was observed in spite of the low TIC concentrations attained (lower than 0.1mmol CL(-1)). The AOB limitation could be successfully modelled using Monod, Tessier and sigmoidal kinetics. The best fit was obtained with sigmoidal kinetics. However, unexpected biomass activity (oxygen consumption) was observed despite a very low TIC concentration (lower than 0.1mmol CL(-1)).

Piggery wastewater treatment using Alcaligenes faecalis strain No. 4 with heterotrophic nitrification and aerobic denitrification

Alcaligenes faecalis strain No. 4, which has heterotrophic nitrification and aerobic denitrification abilities, was used to treat actual piggery wastewater containing high-strength ammonium under aerobic conditions. In a continuous experiment using a solids-free wastewater (SFW) mixed with feces, almost all of the 2000 NH4+ -N mg/L and 12,000 COD mg/L in the wastewater was removed and the ammonium removal rate was approximately 30 mg-N/L/h, which was 5-10 times higher than the rates achieved by other bacteria with the same abilities. The denitrification ratio was more than 65% of removed NH4+ -N, indicating that strain No. 4 exhibited its heterotrophic nitrification and aerobic denitrification abilities in the piggery wastewater.

Characteristics of bacteria showing high denitrification activity in saline wastewater

AIMS

Denitrification efficiency at 10% salinity was compared with that at 2% salinity. The characteristics of bacterial strains isolated from the denitrification system, where an improvement of denitrification efficiency was observed at a high salinity were investigated.

METHODS AND RESULTS

Two continuous feeding denitrification systems for saline solutions of 2% and 10% salinity, were operated. Denitrification efficiency at 10% salinity was higher than that at 2% salinity. The bacterial strains were isolated using the trypticase soy agar (TSA) medium at 30 degrees C. The phylogenetic analysis of 16S rRNA gene sequences of isolates indicated that halophilic species were predominant at 10% salinity.

CONCLUSIONS

The improvement of denitrification efficiency at a high salinity was demonstrated. The strains isolated from the denitrifying system with 10% salinity were halophilic bacteria, Halomonas sp. and Marinobacter sp., suggesting that these bacteria show a high denitrifying activity at 10% salinity.

SIGNIFICANCE AND IMPACT OF THE STUDY

The long-term acclimated sludge used in this study resulted in high denitrification performance at a high salinity, indicating that the design of a high-performance denitrification system for saline wastewater will be possible.

Respirometric calibration and validation of a biological nitrite oxidation model including biomass growth and substrate inhibition

The modelling of the nitrification process of high-strength ammonium wastewater must be designed to consider it as a two-step reaction with substrate inhibition. Consequently, kinetic and stoichiometric parameters of both steps are required. In this work, the second step in the nitrification process was studied: a biological nitrite oxidation model was formulated, calibrated and validated using only oxygen uptake rate (OUR) measurements. The model included biomass growth and substrate inhibition. First, the biomass yield coefficient for nitrite-oxidising biomass was determined. Then, a respirometric experiment with one nitrite pulse of 500 mg N-NO2- L(-1) was performed to estimate the rest of the model parameters. The practical identifiability study showed that the parameters were strongly correlated. Hence, a new experimental design consisting of two consecutive pulses and a delayed third one was designed to improve the parameter identifiability. Both experimental designs were compared using contour plots of the objective function and optimal experimental design criteria for parameter estimation. It was concluded that the parameter identifiability was improved with the new experimental design. Finally, the estimated parameters were validated and the pH effect on the inhibition coefficient was evaluated.

Characteristics of ammonium removal by heterotrophic nitrification-aerobic denitrification by Alcaligenes faecalis No. 4

Alcaligenes faecalis no. 4 has heterotrophic nitrification and aerobic denitrification abilities. By taking the nitrogen balance under different culture conditions, 40-50% of removed NH4+-N was denitrified and about one-half of removed NH4+-N was converted to intracellular nitrogen. The maximum ammonium removal rate of no. 4 (28.9 mg-N/l/h) and its denitrification rate at high-strength NH4+-N of about 1200 ppm in aerated batch experiments at a C/N ratio of 10 were 5-40 times higher than those of other bacteria with the same ability. Only a few percent of the removed ammonium was converted to nitrite, and the main denitrification process was speculated to be via hydroxylamine which was produced by ammonium oxidation.

Nitrification and Denitrification in High-Strength Ammonium by Alcaligenes faecalis

Alcaligenes faecalis sp. No. 4, that has the ability of heterotrophic nitrification and aerobic denitrification in high-strength ammonium at about 1200 mg-N/l, converted about one-half of removed NH4+-N to intracellular nitrogen and nitrified only 3% of the removed NH4+. From the nitrogen balance, 40-50% of removed NH4+-N was estimated to be denitrified. Production of N2 was confirmed by GC-MS and 90% of denitrified products was N2. The maximum ammonium removal rate, 29 mg-N/l h and its denitrification rate in aerated batch experiments, were 5-40 times higher than those of other bacteria with the same ability.

Ammonium exchange in leakage waters of waste dumps using natural zeolite from the Krapina region, Croatia

The paper presents the results of investigating the treatment of leakage waters from waste dumps using activated carbon and natural zeolite clinoptilolite, known as a very selective and efficient cation exchanger for ammonium ions. The results are presented of chemical and physical analyses of leakage waters characterized by a high content of ammonium (820 mg L(-1)) and organic pollutants (1033 mg L(-1) C). Physical and chemical characteristics of zeolite and the exchange of ammonium ions in model and real solutions were determined in laboratory trials. Treatment of leakage water with 0.04-2.5% (w/w) activated carbon (Norit 0.8 Supra) led to a reduction of total organic carbon in leakage water from 1033 to 510 mg L(-1). Pretreatment of leakage water with activated carbon did not improve the exchange of ammonium ions on zeolite. Without pretreatment of leakage water, the exchange of ammonium ions amounted to 4.2 mg NH4+/g zeolite. Addition of activated carbon, regardless of its mass, increased the exchange of ammonium ions to only 5.7 mg NH4+/g zeolite. In the model solution of an equal concentration of ammonium as the real solution, 17.70 mg NH4+/g zeolite was exchanged. Organic pollutants that were not eliminated by activated carbon (most probably components of natural origin) adsorbed to zeolite and prevented the exchange of NH4+ ions, which was also reduced due to the presence of K+ and Ca2+ ions.

Removal of ammoniacal nitrogen (N-NH3) from municipal solid waste leachate by using activated carbon and limestone

The presence of ammoniacal nitrogen (N-NH3) in leachate is one of the problems normally faced by landfill operators. Slow leaching of wastes producing nitrogen and no significant mechanism for transformation of N-NH3 in the landfills causes a high concentration of ammoniacal nitrogen in leachate over a long period of time. A literature review showed that the removal of ammoniacal nitrogen from leachate was not well documented and to date, there were limited studies in Malaysia on this aspect, especially in adsorption treatment. The main objective of the present study was to investigate the suitability of activated carbon, limestone and a mixture of both materials as a filtering medium, in combination with other treatments capable of attenuating ammoniacal nitrogen which is present in significant quantity (between 429 and 1909 mg L(-1)) in one of the landfill sites in Malaysia. The results of the study show that about 40% of ammoniacal nitrogen with concentration of more than 1000 mg L(-1) could be removed either by activated carbon or a mixture of carbon with limestone at mixture ratio of 5:35. This result shows that limestone is potentially useful as a cost-effective medium to replace activated carbon for ammoniacal nitrogen removal at a considerably lower cost.