HRT Conditions Research Articles

Chlortetracycline removal by using hydrogen based membrane biofilm reactor

In the last years, increasing attention has been paid on the presence of antibiotics in aqueous environments due to their ecological damage and potential adverse effects on organisms. Membrane biofilm reactors (MBfR) have been gained a significant popularity as an advanced wastewater treatment technology in removing of organic micro-pollutants. In this study, the performance of H2-MBfR for simultaneous removal of nitrate and chlortetracycline, formation of transformation products and community analysis of the biofilm grown on the gas permeable hollow fiber membranes was evaluated by considering effect of the hydraulic retention time, surface loadings of target pollutants and H2 pressure. The results showed that the simultaneous chlortetracycline (96%) and nitrate removal (99%) took placed successfully under the conditions of 5h HRT and 2psi H2 pressure. It has been determined that the main elimination process was biodegradation and Betaproteobacteria species was responsible for chlortetracycline degradation.

Study of bioleaching under different hydraulic retention time for enhancing the dewaterability of digestate.

Dewatering of kitchen waste digestate is a key problem to solve so as to increase the application of kitchen waste after anaerobic digestion. In this study, the effects of bioleaching under different hydraulic retention time (HRT=2, 2.5, and 3days) on dewaterability of kitchen waste digestate were evaluated. A 12-stage plug flow bioreactor with 180L working volume was used for digestate bioleaching. The bioleached digestate under different HRTs were collected and dewatered by plate-and-frame filter press. The results showed that the moisture contents of digestate cakes were 67.87% at 2days of HRT, 58.06% at 2.5days of HRT, and 54.45% at 3days of HRT, respectively, indicating the longer the HRT, the lower the moisture content of filter cake. Balanced between the cost and practical need, 2.5days can be used as the HRT in engineering application. Under the condition of HRT of 2.5days, the pH, specific resistance to filtration (SRF), capillary suction time (CST), and sedimentation rate of digestate changed from the initial values of 8.08, 210.6s, 23.4×10(12)mkg(-1) and 10% to 3.21, 32.7s, 2.44×10(12)mkg(-1) and 76.8%, respectively. Based on the observations above, the authors conclude that bioleaching technology is an effective method to enhance digestate dewaterability and reduce the cost of subsequent reutilization.

Sulfate bioreduction and elemental sulfur formation in a packed bed reactor

A laboratory scale packed bed reactor (PBR) was fabricated and operated to study its feasibility on SO42∧ reduction. The reactor was packed with polyurethane foam cubes and operated under different feeding and operating conditions of HRT, COD/SO42∧ ratio and SO42∧ concentration. Microbial community characterization showed the presence of sulfate reducing bacteria (SRB) Desulfovibrio species in the bioreactor. The reactor performance was found to be highly efficient than those previously reported at COD/SO42∧ ratio below 0.7 and HRT of 24 h. A maximum SO42∧ reduction of 97% was achieved in the PBR when operated at an HRT of 24 h with SO42∧ concentration of 1500 mg/L and COD/SO42∧ ratio of 0.67. Formation of elemental sulfur was noticed even in absence of any dissolved oxygen which might probably be due to oxidation of sulfides by the intermediate sulfite.

Comparative Modeling of HSF Constructed Wetland Performance With and Without Evapotranspiration and Rainfall

The effects of meteorological parameters, i.e., evapotranspiration (ET) and rainfall (P), on the flow and BOD fate in horizontal subsurface flow constructed wetlands (HSF CW) are presented based on numerical simulation, using the Visual MODFLOW-MT3DMS code, which is based on the finite difference method. This model was used to simulate five HSF CW pilot-scale units, which were constructed and operated in the Laboratory of Ecological Engineering and Technology. Experimental data from these facilities were used to calibrate and verify the numerical procedure. ET was estimated based on a previous study proposing the use of the Blaney-Criddle method, and was introduced in the model. For a characteristic time period, rainfall values from observed events were also entered in the model. The model was then used to test effects of ET and rainfall on effluent concentration under various conditions, showing a more intense effect of ET and a less significant effect of rainfall. It was also used in test runs comparing the performance, without and with ET, under various vegetation, porous media size, HRT and temperature conditions.

Enhanced struvite recovery from wastewater using a novel cone-inserted fluidized bed reactor

The feasibility of struvite recovery at low (12.5 mg/L) and high (120 mg/L) phosphorus concentrations was studied by constructing a novel fluidized bed reactor with cones (FBRwc) and without cones (FBRwoc). The crystallization process was continuously operated for 133 days under different hydraulic retention times (HRT = 1–10 hr), pH (7.5–10), and molar ratios of Mg/P (0.75–1.75), N/P (1–10) and Ca/Mg (0–2). The optimum operating conditions of HRT, pH, Mg/P and N/P molar ratios were found to be 2 hr, 9, 1.25, and 7.5, respectively. Under these optimum conditions, the phosphorus precipitation efficiencies of FBRwc were 93% for low and 98% for high phosphorus influent; however, the efficiencies were 78% and 81% for FBRwoc, respectively. Due to crystal losses at each junction (17%–31%), the crystal recovery efficiency of FBRwoc was relatively low (47%–65%) for both influent concentrations. However, the losses were minimal in FBRwc, which showed 75% and 92% crystal recovery for low and high phosphorus concentrations, respectively. At low calcium concentration, crystal chemical analysis showed the product to be pure struvite (> 99%). The scanning electron microscope and X-ray diffraction results further confirmed that the crystal recovered from FBRwc contained pure struvite, which could be considered a high quality fertilizer. Except HRT, all parameters (pH, Mg/P, N/P and Ca/Mg) were found to be influencing factors for FBRwc performance. Overall, inserting cones in each part of the reactor played a significant role in enhancing struvite recovery from a wide range of phosphorus-containing wastewater.

Effects of the Filler Properties on Removal Nitrogen of Wastewater in Hybrid Biofilm-Activated Sludge Process

To develop the proper filler for improving removal efficiency of ammonia nitrogen in the activated sludge process of wastewater treatment, the effects of the filler properties and treatment conditions on removal efficiency of ammonia nitrogen in hybrid biofilm-activated sludge process were investigated by the lab-scale test and pilot-scale test. Moreover, the feasibility of simultaneous nitrification and denitrification (SND) was explored with biofilm treatment for chemical poor-biological wastewater. The results showed that SND occurred in the aerobic section. The effluent total basicity (TB) in biofilm process was more than 2mmol / L, higher than activated sludge process. Correspondingly, the effluent TB in activated sludge process was about 0.1mmol / L, and nitrate produced by activated sludge process was 30 mg/L higher than biofilm process. Under the condition of HRT of 24 h for hydrolysis-acidification tank, HRT of 4 h for anoxic tank and HRT of 16 h for aerobic tank, effluent NOˉx-N with combination type of filler in biofilm process was 20mg/L less than that with the activated sludge process. TB with combination type of filler in biofilm process was 2mmol/L less than that with the activated sludge process. Nitrogen removal efficiency was 10.46% with SJ-1 type of filler (made in Jiangsu Suzhou Purification Group Co.,Ltd) more than with combination type of filler. The effluent NOˉx-N concentrations was less than.15mg/L in biofilm process with SJ-1 type of filler. A practical mathematical model with the A/O process was developed for predicting removal effects, which can provide a theoretical guidance for wastewater treatment and engineering design.

膜生物反应器与生物接触氧化两种工艺处理食堂废水效能对比研究

本文以实际的食堂废水为处理对象，对比考察了在不同的水力停留时间(6 h、8 h、10 h)条件下，膜生物反应器(MBR)和生物接触氧化(BCO)两种工艺对食堂废水的净化效能。试验结果表明：两种工艺对食堂废水均有较好的净化效能，其中MBR工艺出水和BCO工艺出水中动植物油浓度最低为16.4 mg/L和68.9 mg/L，动植物油的去除率分别可达99.5和%97.8%；COD的去除率均在90%以上，其出水COD浓度最低为15.7 mg/L和21.3 mg/L；两种工艺对NH3-N的去除率差异不大，出水NH3-N浓度在1 mg/L以下；TP去除率均在80%以上，出水TP浓度在0.4 mg/L左右。TN的去除率不够理想，仅为20%左右。在不同的HRT下，两种组合工艺对NH3-N和TN的去除率差异不大，而TP在高HRT条件下的去除率不稳定，因此确定MBR和BCO两种工艺较为适宜的HRT为6 h。 In this paper, the actual canteen wastewater was treated with membrane bioreactor (MBR) and biological contact oxidation (BCO), and the treatment efficiency of canteen wastewater at different hydraulic retention time (6 h, 8 h, 10 h) was studied. The experimental results showed that both kinds of the two combined processes have good purification efficiencies to canteen wastewater. The animal and plant oil concentrations in the effluent of MBR and BCO process were 16.4 mg/L and 68.9 mg/L; the removal rates of animal and plant oil can reach 99.5% and 97.8%. The removal rates of COD were both above 90%, and the effluent COD concentration was at 15.7 mg/L and 21.3 mg/L. There was no big difference in the removal of NH3-N in the two kinds of combined process, and the NH3-N concentration in the effluent was below 1 mg/L. The removal rate of TP was above 80% and the TP concentration in the effluent was about 0.4 mg/L. The removal rate of TN was not ideal, only about 20%. In different HRT conditions, there was no big difference in NH3-N and TN removal rate in the two kinds of combined process, but the removal rate of TP in high HRT condition was unstable. Therefore, the more suitable HRT of MBR process and BCO process was determined at 6 h.

Correlationship of Vertical Distribution for Ammonia Ion, Nitrate Ion and Nitrifying Bacteria in a Fixed Bed Nitrifying Biofilm

The vertical distributions of nitrifying bacteria in aerobic fixed biofilm were investigated to evaluate the relationship between nitrification performance and microbial community at different HRT. Fluorescent in situ hybridization (FISH) and portable ion selective microelectrode system were adopted to analyze microbial communities and ions profiles according to the biofilm depth. Cilia media packed MLE (Modified Ludzack-Ettinger) like reactor composed of anoxic, aerobic I/II was operated with synthetic wastewater having COD 200 mg/L and <TEX>$NH_4{^+}$</TEX>-N mg/L at HRT of 6 hrs and 4 hrs. Total biofilm thickness of aerobic I, II reactor at 4 hrs condition was over two times than that of 6 hrs condition due to the sufficient substrate supply at 4 hrs condition (6 hrs; aerobic I 380 <TEX>${\mu}m$</TEX> and II 400 <TEX>${\mu}m$</TEX>, 4 hrs; aerobic I 830 <TEX>${\mu}m$</TEX> and II 1040 <TEX>${\mu}m$</TEX>). As deepen the biofilm detection point, the ratio of ammonia oxidizing bacteria (AOB) was decreased while the ratio of nitrite oxidizing bacteria (NOB) was maintained similar distribution at both HRT condition. The ratio of AOB was higher at 4 hrs than 6 hrs condition and <TEX>$NH_4{^+}$</TEX>-N removal efficiency was also higher at 4 hrs with 89.2% than 65.4% of 6 hrs. However, the ratio of NOB was decreased when HRT was reduced from 6 hrs to 4 hrs and <TEX>$NO_2{^-}$</TEX>-N accumulation was observed at 4 hrs condition. Therefore, it is considered that insufficient HRT condition could supply sufficient substrate and enrichment of AOB in all depth of fixed biofilm but cause decrease of NOB and nitrite accumulation.

Treatment Effect of Coking Wastewater Using Three-Phase Biological Fluid-Bed with New Ultrastructure Biological Carriers Based on Properties of Biological Materials

The degradation of COD and ammonia nitrogen (NH3-N) in coking wastewater was researched using the new ultrastructure biological carriers in three-phase aerobic biological fluid-bed. The results show that the optimum conditions of the new biological carriers are as follows: HRT of 20 h, neutrality skew alkaline pH (about 7.5) and dissolved oxygen (DO) of 2~5mg/L. Under the optimum conditions, the removal efficiency of COD and NH3-N can reach 82% and 87%, respectively, when the influent concentration of COD and NH3-N is about 3000 mg/L and 60mg/L. At the same time, comparison with the activated sludge process and common biological ceramisite carriers, it is found that the most excellent treatment effect and the strongest resistance to impact are obtained under the condition of the shortest HRT in this new ultrastructure biological carriers reactor, and the effluent of two-stage reactors in series can reach the first national discharge standard, which will has a wide application prospect.

Industrial wastewater treatment by on-site pilot static granular bed reactor (SGBR)

The on-site pilot-scale Static Granular Bed Reactor (SGBR) was used to treat the dairy processing wastewater at the Tulare Industrial Wastewater Treatment Plant (IWTP). A pilot unit with approximately 42.5 m3 of active volume was operated for 7 months on a continuous basis with a range of 9 to 48 h HRT condition at ambient temperature. Throughout the whole study, COD and BOD5 removal was consistently over 90% under a broad range of organic loading conditions ranging from 0.63 to 9.72 kg/m3/d. TSS removal was also greater than 80% on average. In terms of organic removal, the SGBR system was robust to the temperature variations ranging from 10 to 29 °C. The adequate periodic backwashing consistently provided the maintenance of a head loss and the wastewater level in the reactor. Based on these results, the SGBR seems to be an excellent alternative for the required pretreatment system from the Tulare IWTP. Several benefits for IWTP could be provided by a full scale application of SGBR due to its simple design and operational advantages over conventional high rate anaerobic systems.

Study on A&lt;sup&gt;2&lt;/sup&gt;O Method for Co-Treatment of Landfill Leachate and Municipal Sewage

To solve the problem of huge investment and high difficulty of individually treating landfill leachate, the experiment adopted A2O simulated wastewater treatment plant to treat landfill leachate combined with municipal sewage.Under the conditions of 11h HRT, 1.0-2.0mg/L DO concentration, 200% mixture reflux proportion, 80% sludge reflux proportion and 20d sludge age, adding langdfill leachate to municipal sewage with the proportion of 1:1500, 1:1000 and 1:600, the effluent concentration can achieve the first order A standard of Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant. When the proportions come to 1:400 and 1:200,the effluent quality can’t reach the standard. After a comprehensive consideration of water quality and landfill leachate treatment amount in practice, we can draw a conclusion that the 1:600 proportion is the most suitable one of adding landfill leachate to municipal sewage.

Start-up Experiment of Ethanol-Type Fermentation of Pretreated Surplus Sludge

This paper study on surplus sludge of high pressure combined with thermal hydrolysis; investigate the start-up of ethanol-type fermentation. The results show that under the condition of HRT 3.6 d, the organic loading rate for 4.40kgVS/m3•d, the pH of acidogenic phase should be controlled in the scale of 4.0～4.5, the acidogenic phase could stable at the ethanol-type fermentation stage after the experiment lasting for 22d, the contractions of outlet sludge in VFA reached 3820～3980mg/L, in which the sum of ethanol and acetic could reach more than 72% VFA, the specific hydrogen production of acidogenic phase in this condition achieved 0.018 L•H2/g•VS.

Municipal Wastewater Treatment in a New Type Bio-Carrier Reactor

Abstract A newly designed bio-carrier was used in an A/O system to investigate nutrients removal from municipal wastewater. The system was operated for 120 days including two successive phases. Only bio-carrier was used in Phase I without suspended sludge. Suspended sludge was combined with biofilm in Phase II. Results showed that in the whole process, removal efficiency of COD, NH 4 + -N and TN could be respectively up to 76.0%, 72.6% and 43.3%. A/O system obtained the best treatment effect under the condition of HRT = 16.7 h and internal flux radio = 150%. And in the same conditions, suspended sludge-biofilm in Phase II performed a better removal effect than biofilm in Phase I. In addition, a simplified mathematical model was proposed, which provided an accurate tool for describing the steady-state suspended sludge-biofilm system.

Performance of a ZVI-UASB reactor for azo dye wastewater treatment

BACKGROUND: Zero valent iron (ZVI) is expected to be helpful for creating an enhanced anaerobic environment that might improve the performance of the anaerobic process. Based on this idea, a ZVI packed upflow anaerobic sludge blanket reactor (ZVI-UASB) was developed to enhance azo dye wastewater treatment. RESULTS: The ZVI-UASB reactor was less influenced by a decrease in the operational temperature from 35 °C to 25 °C than a reference UASB reactor that did not contain ZVI. In addition, chemical oxygen demand (COD) and color removal efficiencies of the ZVI-UASB reactor at an HRT of 12 h exceeded those of the reference reactor at an HRT of 24 h. The hydraulic circulation in the ZVI bed enhanced the function of ZVI so that it improved the COD and color removal efficiencies. Moreover, fluorescence in situ hybridization experiments revealed that the abundance of Archaea in the sludge of the ZVI bed was significantly higher than that at the reactor bottom, which made the reactor capable of greater COD removal under low temperature and short HRT conditions. CONCLUSION: This ZVI-UASB reactor could adapt well to changes in the operational conditions during wastewater treatment. Copyright © 2010 Society of Chemical Industry

Hydraulic retention time impact of treated recirculated leachate on the hydrolytic kinetic rate of coffee pulp in an acidogenic reactor

This study attempted to investigate the impact of HRT of treated leachate recirculation on hydrolysis solubilization rate of coffee pulp in an acidogenic reactor. Coffee pulp presents more than 70% of organic matter and around of 30% of lignin and cellulose. Five lab scale reactors of 20 litres were used. Each reactor was fed with 5 kg of fresh coffee pulp and anaerobic sludge was used as inoculate. HRT of 0.5, 1, 3 and 10 days were applied. Each experiment shows that Total, Soluble and VFA COD appear rapidly in the removed leachate. HRT have a great impact on hydrolytic rate with an optimal value of 32,000 mg x L(-1) x d(-1).Low HRT increases hydrolysis rate and in consequence reduces duration of the hydrolytic phase. Also composition and concentration of VFA are influenced by HRT. Low ones favour acetic acid production and high ones permit the production of butyric. Low HRT generates leachate more easily fermentable. Efficiency of solubilization and acidification are independent of the HRT and present average values of 78% and 65% respectively. By batch feeding solid and continuous recirculation of treated leachate, HRT and SRT could be dissociated, where solid had a very high retention without problems of load, mixing and inhibition, and liquid could be recirculated with a very high rate. Under these low HRT condition, the first reactor of a two stage anaerobic system could reduces the hydrolysis duration of organic solid waste like coffee pulp and generate an optimal leachate for the methanization process.

Removal of organic pollutants from 2,2′,5,5′-tetrachlorobenzidine (TCB) industrial wastewater by micro-electrochemical oxidation and air-stripping

A feasible method for treatment of the wastewater from the two-staged neutralization in 2,2′,5,5′-tetrachlorobenzidine (TCB) manufacturing processes, a refractory dye intermediate effluents, based on combined micro-electrochemical oxidation or iron-chipping filtration (ICF) and air-stripping reactor (ASR), was developed. On conditions of HRT 1 h, pH 3.0 in ICF and HRT 38 h, gas–liquid ratio 15, pH 6.0–8.65, temperature 26 °C in ASR, the overall COD, color, TCB and NH 4 +-N removal were 96.8%, 91%, 87.61% and 62%, respectively, during the treatment of TCB wastewater from the two-staged neutralization dissolved by methanol. The averaged 18.3%, 81.7% of the total degraded COD, 35.2%, 64.8% of TCB were carried out in ICF and ASR, respectively. NH 4 +-N removal was finished mainly in ASR. The experimental results indicated that the combined micro-electrochemical oxidation and air-stripping process performed good treatment of COD, color, TCB and NH 4 +-N removal in TCB wastewater from the two-staged neutralization dissolved by ethanol or acetone, came up the discharge standard in China. But the TCB wastewater from the two-staged neutralization dissolved by methanol should be deeply treated before discharged.

Biodegradation kinetics of high strength oily pet food wastewater in a membrane-coupled bioreactor (MBR)

Aerobic respirometric experiments were conducted at a temperature of 40 °C to determine biokinetic parameters describing growth and decay of aerobic biomass acclimatized in a membrane-coupled bioreactor (MBR). The kinetic parameters were determined with the volatile fatty acids (VFA) acetic acid and propionic acid as substrates as well as the soluble fraction of a high strength rendering wastewater as substrate. The oxygen uptake rate (OUR) and cumulative oxygen uptake (OU) recorded during the experiments were fitted to Monod kinetic model to obtain true yield ( Y t), intrinsic maximum substrate removal ( k), half-saturation constant ( K s) and endogenous decay coefficient ( k d). K s were determined to be 181, 271 and 806 mg COD l −1 and k as 1.89, 1.08 and 0.85 mg COD mg VSS −1 h −1 for acetate, propionate and rendering wastewater, respectively. The continuous-flow MBR was operated under two HRT conditions, 10 and 5 d, attaining high BOD removal efficiencies of 99% and 87%, respectively. The observed yield in the MBR was 0.03 g VSS g −1 COD.

Enhanced ammonia nitrogen removal using consistent biological regeneration and ammonium exchange of zeolite in modified SBR process

The modified zeo-SBR is recommended for a new nitrogen removal process that has a special function of consistent ammonium exchange and bioregeneration of zeolite-floc. Three sets of sequencing batch reactors, control, zeo-SBR, and modified zeo-SBR were tested to assess nitrogen removal efficiency. The control reactor consisted of anoxic-fill, aeration-mixing, settling, and decanting/idle phases, meaning that nitrogen removal efficiency was dependent on the decanting volume in a cycle. The zeo-SBR reactor was operated in the same way as the control reactor, except for daily addition of powdered zeolite in the SBR reactor. The operating order sequences in the zeo-SBR were changed in the modified zeo-SBR. Anoxic-fill phase was followed by aeration-mixing phase in the zeo-SBR, while aeration-mixing phase was followed by anoxic-fill phase in the modified zeo-SBR to carry NH 4 +-N over to the next operational cycle and to reduce total nitrogen concentration in the effluent. In the modified zeo-SBR, nitrification and biological regeneration occurred during the initial aeration-mixing phase, while denitrification and ammonium adsorption occurred in the following anoxic-fill phase. The changed operational sequence in the modified zeo-SBR to adapt the ammonium adsorption and biological regeneration of the zeolite-floc could enhance nitrogen removal efficiency. As a result of the continuous operation, the nitrogen removal efficiencies of the control and zeo-SBR were in 68.5–70.9%, based on the 33% of decanting volume for a cycle. The zeo-SBR showed a consistent ammonium exchange and bio-regeneration in the anoxic-fill and aeration-mixing phases, respectively. Meanwhile, the effluent total nitrogen of the modified zeo-SBR showed 50–60 mg N/L through ammonium adsorption of the zeolite-floc when the influent ammonium concentration was 315 mg N/L, indicating the T-N removal efficiency was enhanced over 10% in the same HRT and SRT conditions as those of control and zeo-SBR reactors. The ammonium adsorption capacity was found to be 6–7 mg NH 4 +-N/g FSS that is equivalent to 40 mg NH 4 +-N/L of ammonium nitrogen removal.

Simultaneous removal of nitrogen and phosphorus with A2/O process using immobilized media

It is necessary to introduce nitrogen and phosphorus removal processes in the existing wastewater treatment plants of Fukuoka City to improve the water quality of Hakata Bay. An A2/O (anaerobic-anoxic-oxic) process using immobilized media is proposed here, as a high-end technology to meet stricter discharge standards when faced with treatment space limitations. In order to investigate the applicability of the process, a pilot-scale study using municipal wastewater was conducted. Fluidized immobilization media were added to the aerobic reactor to maintain a high concentration of nitrifying bacteria and nitrification rate. Relationships between nutrient removal performance and varied operating conditions were examined. The results of the pilot plant test indicated that the process performs well for removal of nitrogen and phosphorus. Under the condition of HRT = 8 hr, it was possible to obtain an effluent water quality as follows: T-N<8.0 mg/L; T-P<1.0 mg/L. It was observed that reaction time needed for a complete nitrification was shortened by the addition of immobilized media to the aerobic reactor, and longer reaction time would be needed for a completed phosphorus uptake process other than complete nitrification in an aerobic tank. Therefore, the phosphorus uptake rate, as well as nitrification process, should be considered as one of the important factors affecting the design parameters of an aerobic reactor.

Removal of phosphate, magnesium and calcium from swine wastewater through crystallization enhanced by aeration

In order to confirm the possibility of removing PO 4-P, Mg and Ca from swine wastewater through artificial crystallization by aeration, laboratory and pilot scale experiments were carried out using actual swine wastewater. The pH of swine wastewater increased up to approximately 8.5 with continuous aeration, and a large part of the soluble PO 4-P, Mg and Ca was crystallized. The ingredients of the crystals were estimated as MAP and HAP according to their mole ratio of NH 4-N, PO 4-P, Mg and Ca. The sedimentation speed of crystals in swine wastewater was about 3 m h −1, and over 90% of them had settled after standing 1 h. A pilot scale reactor with the dual functions of crystallization by aeration and settling was operated continuously using actual swine wastewater, with aeration conditions of HRT 4.1 h and 26 m 3 air h −1 m −2 cross section (18 m 3 air h −1 m −3 volume). During 50 days of operation, pH at the aeration column held stable at 8.0, and 65% of PO 4-P, 51% of Mg, and 34% of Ca were removed.