Juan Carlos Leyva-Díaz

Moving bed biofilm reactor to treat wastewater

This review carries out a comparative study of advanced technologies to design, upgrade and rehabilitate wastewater treatment plants. The study analyzed the relevant researches in the last years about the moving bed biofilm reactor process with only attached biomass and with hybrid biomass, which combined attached and suspended growth; both could be coupled with a secondary settling tank or microfiltration/ultrafiltration membrane as a separation system. The physical process of membrane separation improved the organic matter and NH4+-N removal efficiencies compared with the settling tank. In particular, the pure moving bed biofilm reactor–membrane bioreactor showed average chemical oxygen demand, biochemical oxygen demand on the fifth day and total nitrogen removal efficiencies of 88.32, 90.84 and 60.17%, respectively, and the hybrid moving bed biofilm reactor–membrane bioreactor had mean chemical oxygen demand, biochemical oxygen demand on the fifth day and total nitrogen reduction percentages of 91.18, 97.34 and 68.71%, respectively. Moreover, the hybrid moving bed biofilm reactor–membrane bioreactor showed the best efficiency regarding organic matter removal for low hydraulic retention times, so this system would enable the rehabilitation of activated sludge plants and membrane bioreactors that did not comply with legislation regarding organic matter removal. As the pure moving bed biofilm reactor–membrane bioreactor performed better than the hybrid moving bed biofilm reactor–membrane bioreactor concerning the total nitrogen removal under low hydraulic retention times, this system could be used to adapt wastewater treatment plants whose effluent was flowed into sensitive zones where total nitrogen concentration was restricted. This technology has been reliably used to upgrade overloaded existing conventional activated sludge plants, to treat wastewater coming from textile, petrochemical, pharmaceutical, paper mill or hospital effluents, to treat wastewater containing recalcitrant compounds efficiently, and to treat wastewater with high salinity and/or low and high temperatures.

Isolation and metagenomic characterization of bacteria associated with calcium carbonate and struvite precipitation in a pure moving bed biofilm reactor-membrane bioreactor

A bench-scale pure moving bed bioreactor-membrane bioreactor (MBBR-MBR) used for the treatment of urban wastewater was analyzed for the identification of bacterial strains with the potential capacity for calcium carbonate and struvite biomineral formation. Isolation of mineral-forming strains on calcium carbonate and struvite media revealed six major colonies with a carbonate or struvite precipitation capacity in the biofouling on the membrane surface and showed that heterotrophic bacteria with the ability to precipitate calcium carbonate and struvite constituted ~7.5% of the total platable bacteria. These belonged to the genera Lysinibacillus, Trichococcus, Comamomas and Bacillus. Pyrosequencing analysis of the microbial communities in the suspended cells and membrane biofouling showed a high degree of similarity in all the samples collected with respect to bacterial assemblage. The study of operational taxonomic units (OTUs) identified through pyrosequencing suggested that ~21% of the total bacterial community identified in the biofouling could potentially form calcium carbonate or struvite crystals in the pure MBBR-MBR system used for the treatment of urban wastewater.

Combined treatment of textile wastewater by coagulation–flocculation and advanced oxidation processes

AbstractTextile wastewater is one of the main environmental pollutants which exist in our society. Textile effluents cause great concern due to the alteration of properties of water bodies such as differences in temperature, organic load, pH, colour and turbidity. Turbidity is one of the most important parameters that should be removed from industrial wastewater because the penetration of ultraviolet (UV) light into the water body can be affected. As a consequence, the main aim of this research was to study the improvements of the efficiency of advanced oxidation processes (AOPs) with the introduction of a coagulation–flocculation (CF) as a pre-treatment to remove the turbidity of textile wastewater. The experiments were carried out with five industrial coagulants under different concentrations. The turbidity was removed to a level of almost 99% with one of the coagulants (FLOCUSOL-PA/18). The total organic carbon (TOC) and colour removals were studied for each AOP after the CF process in this research. T...

Linkage of microbial kinetics and bacterial community structure of MBR and hybrid MBBR–MBR systems to treat salinity‐amended urban wastewater

Three pilot‐scale bioreactors were started up and operated under salinity‐amended urban wastewater feeding. The bioreactors were configured as membrane bioreactor and two different hybrid, moving bed biofilm reactor‐membrane bioreactor and operated with a hydraulic retention time of 9.5 h, a solid residence time of 11.75 days and a total solids concentration of 2500 mg L−1. The three systems showed excellent performance in suspended solids, BOD5, and COD removal (values of 96–100%, 97–99%, and 88–90%, respectively), but poor nitrogen removal (values of 20–30%). The bacterial community structure during the start‐up phase and the stabilization phase were different, as showed by β‐diversity analyses. The differences between aerobic and anoxic biomass—and between suspended and attached biomass—were higher at the start‐up phase than at the stabilization phase. The start‐up phase showed high abundances of Chiayiivirga (mean values around 3–12% relative abundance) and Luteimonas (5–8%), but in the stabilization phase, the domination belonged to Thermomonas (3–14%), Nitrobacter (3–7%), Ottowia (3–11.5%), and Comamonas (2–6%), among others. Multivariate redundancy analyses showed that Thermomonas and Nitrosomonas were positively correlated with fast autotrophic kinetics, while Caulobacter and Ottowia were positively correlated with fast heterotrophic kinetics. Nitrobacter, Rhodanobacter, and Comamonas were positively correlated with fast autotrophic and heterotrophic kinetics.

Effects of temperature on the permeability and critical flux of the membrane in a moving bed membrane bioreactor

AbstractEffects of temperature on the permeate flux and the permeability of the membrane have been studied in a membrane bioreactor system with a moving bed pilot plant to treat real urban wastewater. In the present study, the permeability of the membrane has been determined under four different suspended solids concentrations and three different degrees of fouling in order to compare the effects of the temperature in different operational conditions. The permeate flux, critical flux and permeability of the membrane at seven different temperatures between 10 and 35°C have been checked. The study showed that the permeate flux increased to 19.2 and 21.2% between 10 and 15°C and between 15 and 20°C respectively, which was higher than the 8.70% obtained between 20 and 25°C, and similarly it increased to 15.6 and 15.6% obtained between 25 and 30°C and between 30 and 35°C, respectively. This trend has been also observed in critical flux values, under the different conditions of suspended solids and fouling degr...

Influence of sludge retention time and temperature on the sludge removal in a submerged membrane bioreactor: Comparative study between pure oxygen and air to supply aerobic conditions

Performance of a bench-scale wastewater treatment plant, which consisted of a membrane bioreactor, was monitored daily using pure oxygen and air to supply aerobic conditions with the aim of studying the increases of the aeration and sludge removal efficiencies and the effect of the temperature. The results showed the capacity of membrane bioreactor systems for removing organic matter. The alpha-factors of the aeration were determined for six different MLSS concentrations in order to understand the system working when pure oxygen and air were used to supply aerobic conditions in the system. Aeration efficiency was increased between 30.7 and 45.9% when pure oxygen was used in the operation conditions (a hydraulic retention time of 12 h and MLSS concentrations between 4,018 and 11,192 mg/L). Sludge removal efficiency increased incrementally, from 0.2 to 1.5% when pure oxygen was used at low sludge retention time and from 1.5% to 15.4% at medium sludge retention time when temperature conditions were lower than 20°C. Moreover, the difference between calculated and experimental sludge retention time was lesser when pure oxygen was used to provide aerobic conditions, so the influence of the temperature decreased when the pure oxygen was used. These results showed the convenience of using pure oxygen due to the improvement in the performance of the system.

Influence of temperature on the start-up of membrane bioreactor: kinetic study

The start-up phase of a membrane bioreactor (MBR) for municipal wastewater treatment was studied to determine the effect of temperature on the organic matter removal and heterotrophic kinetics. The MBR system was analyzed during four start-up phases with values of hydraulic retention time (HRT) of 6 h and 10 h, mixed liquor suspended solids (MLSS) concentrations of 4,000 mg L-1 and 7,000 mg L-1 in the steady state, and temperature values of 11.5, 14.2, 22.9 and 30.1 °C. The influence of temperature on the biological process of organic matter removal was determined through the Arrhenius equation and Monod model. At the most favorable operation conditions of HRT (10 h) and MLSS (7,000 mg L-1) corresponding to phase 4, the effect of these variables dominated over the temperature. Heterotrophic biomass from phase 2 (HRT = 10 h, MLSS = 4,000 mg L-1 and T = 30.1 °C) had the highest values of chemical oxygen demand (COD) degradation rate (rsu,H), implying less time to remove organic matter and shorter duration of the start-up phase.

Effect of Salinity Variation on the Autotrophic Kinetics of the Start-up of Membrane Bioreactor and Hybrid Moving Bed Biofilm Reactor-Membrane Bioreactor at Low Hydraulic Retention Time

A membrane bioreactor (MBR) and a hybrid moving bed biofilm reactor-membrane bioreactor (hybrid MBBR-MBR) for municipal wastewater treatment were studied to determine the effect of salinity on nitrogen removal and autotrophic kinetics. The biological systems were analyzed during the start-up phase with a hydraulic retention time (HRT) of 6 h, total biomass concentration of 2,500 mg L-1 in the steady state, and electric conductivities of 1.05 mS cm-1 for MBR and hybrid MBBR-MBR working under regular salinity and conductivity variations of 1.2-6.5 mS cm-1 for MBR and hybrid MBBR-MBR operating at variable salinity. The variable salinity affected the autotrophic biomass, which caused a reduction of the nitrogen degradation rate, an increase of time to remove ammonium from municipal wastewater and longer duration of the start-up phase for the MBR and hybrid MBBR-MBR.

Impact of Hydraulic Retention Time on MBR and Hybrid MBBR-MBR Systems Through Microbiological Approach: TGGE and Enzyme Activities

The microbial community structure and the enzyme activities of a MBR and two hybrid MBBR-MBR systems were analyzed at two different hydraulic retention times. The TGGE fingerprinting showed that the microbial community structure was deeply dependent on the operational HRT. The activities of acid phosphatase, basic phosphatase and α-glucosidase enzyme activities also were affected by the different HRT. A multivariate redundancy analysis showed that the first of these was positively correlated with the HRT, while the other two were negatively correlated. In this sense, the microbiological approach could successfully explain the influence of the HRT over the bacterial communities and activities in the MBR and hybrid MBBR-MBR systems analyzed.

Removal Performance of Organic Matter of MBR and Hybrid MBBR-MBR Systems During Start-up and Stabilization Phases Treating Variable Salinity Urban Wastewater

A MBR and two hybrid MBBR-MBR with different configurations were used for the treatment of variable salinity wastewater. The systems were started-up and operated until stabilization conditions while being fed with salinity-amended urban wastewater. The salinity-amended urban wastewater was generated by the mixture of urban wastewater and salinity-amended tap water to obtain a feeding with salinity in the range of 1–6.5 mS cm−1. The three bioreactors were subjected to cyclical salinity variations with a cycle consisting of 6 h at 6.5 mS cm−1 salinity and 6 h at regular wastewater salinity. The system was evaluated for its performance in organic matter removal by COD and BOD5 measurements. Also, the kinetics of its heterotrophic biomass was characterized by the means of respirometric tests. The results showed a very good removal of COD and BOD5, with the MBBR-MBRanox showing the highest performances. The heterotrophic kinetics were higher at lower total solids concentrations with the MBR system having the fastest kinetics during the start-up. These results will be of use for the future application of MBR and hybrid MBBR-MBR systems to the treatment of variable salinity wastewater.