RESUMEN
The cost-effective recovery of phosphate is of great significance to the mitigation of phosphorus resource depletion crisis. The electrochemical-decomposition of dolomite was developed to recover phosphate and ammonium from aqueous solution. The dolomite ore is mainly composed of CaMg(CO3)2 (53.73%), CaCO3 (28.93%) and SiO2 (16.59%). The continuous release of Mg2+ and Ca2+ were achieved by electrochemically decomposing dolomite ore, accompanied by the generation of base solution (9.0-10.5). The main factors affecting the recovery performance of phosphate (PO4-P) and ammonium (NH4-N) are current, initial concentration of PO4-P and NH4-N, initial pH of feed solution and feed rate. For a 30-d operation, the recovery rate of PO4-P was maintained at 90-97% and that of NH4-N at 50-60% under optimized operating conditions. The recovered product had low water solubility but high citric-acid-soluble, and was proposed as a slow-release fertilizer for crops. The proposed process as a simple, effective and green route may serve as a new strategy for recovering PO4-P and NH4-N from wastewaters.
Asunto(s)
Compuestos de Amonio/química , Carbonato de Calcio/química , Técnicas Electroquímicas/métodos , Magnesio/química , Fosfatos/química , Eliminación de Residuos Líquidos/métodos , Compuestos de Amonio/aislamiento & purificación , Calcio/química , Electrodos , Fertilizantes , Concentración de Iones de Hidrógeno , Fosfatos/aislamiento & purificación , Fósforo/química , Dióxido de Silicio , Soluciones , Aguas Residuales/química , Contaminantes Químicos del Agua/químicaRESUMEN
In this study, biofilters (BFs) packed with inorganic (ceramsite and lava rock) and organic (fibrous carrier and biological ball) materials were applied in a tide-flow mode at three flooded/drained (F/D) time ratios (16/8â¯h, 12/12â¯h and 8/16â¯h) to treat heavily polluted river water. The results showed that higher ammonium and phosphorus removals were achieved with BFs filled with ceramsite (95-97% and 76-77%) and lava rock (87-92% and 84-94%), while fibrous carrier-packed BFs obtained better total nitrogen removal (37-44%). Moreover, the F/D time ratio of 16/8â¯h was slightly preferable for pollutant removal. High-throughput sequencing analysis illustrated that the relative abundance of potential denitrifiers that developed on organic media was much higher than those on inorganic substrates. The results indicated that the combination of inorganic materials and fibrous carriers as substrates could be an effective strategy for enhancing overall pollutant removal in BFs.
Asunto(s)
Filtración/métodos , Microbiota , Ríos/química , Compuestos de Amonio/aislamiento & purificación , Bacterias , Nitrógeno/aislamiento & purificación , Fósforo/aislamiento & purificación , Contaminación del Agua/análisisRESUMEN
The activated sludge process of the anaerobic/oxic (A/O) process has a good denitrification performance because it can make full use of the carbon source in the original sewage, and the denitrification can provide alkalinity for aerobic nitrification. The traditional constructed soil rapid infiltration (CSRI) system, on the other hand, has a poor nitrogen removal effect. Dividing the traditional CSRI system into two sections, one performs denitrification as an anoxic section, while the other performs nitrification as an aerobic section and is placed after the anoxic section. The nitrification liquid of the effluent from the aerobic section is mixed with the original wastewater and enters the anoxic section for denitrification. We expected that this would be improved by combining CSRI with a pre-denitrification step that would make full use of the carbon source in the original sewage. In a small-scale experimental model, the removal efficiencies of nitrogen, in the form of ammonium, nitrate, and total nitrogen (TN), as well as chemical oxygen demand (COD), were determined. The hydraulic load was varied, while the backflow reflux capacity was kept constant, to determine the effect on the pre-denitrification process. An average removal rate of 95.4% for NH4âº-N and 96% for COD could be obtained when a hydraulic load of 80 cm³(cm²·d)-1 and a reflux ratio of 75% were applied. Under these conditions, the average removal rate of TN was 77.4%, which is much higher than what can be typically achieved with conventional CSRI systems.
Asunto(s)
Desnitrificación , Administración de Residuos/métodos , Compuestos de Amonio/aislamiento & purificación , Análisis de la Demanda Biológica de Oxígeno , Reactores Biológicos , Carbono , Nitrificación , Nitrógeno/aislamiento & purificación , Aguas del Alcantarillado , Suelo , Aguas ResidualesRESUMEN
Packed cartridges have been widely used in solid-phase extraction. However, there are still some drawbacks, such as they are blocked easily and the method is time-consuming. In view of the advantages of monoliths, a monolithic extraction material has been directly synthesized in a glass syringe without any gap between the monolith and syringe inner wall. The monolithic syringe was modified with graphene oxide by loading graphene oxide dispersion onto it. The content of graphene oxide and the surface topography of the monolith have been evaluated by elemental analysis and scanning electron microscopy, respectively, which confirmed the successful modification. This prepared graphene oxide-modified monolithic syringe was directly used as a traditional solid-phase extraction cartridge. As expected, it shows good permeability and excellent capability for the extraction of quaternary ammonium alkaloids. The sample loading velocity (1-6 mL/min) does not affect the recovery. Under the optimal conditions, good linearities (R = 0.9992-0.9998) were obtained for five quaternary ammonium alkaloids, and the limits of detection and quantification were 0.5-1 and 1-2 µg/L, respectively. The proposed method was successfully applied for the analysis of quaternary ammonium alkaloids in Chinese patent medicine.
Asunto(s)
Alcaloides/aislamiento & purificación , Compuestos de Amonio/aislamiento & purificación , Medicamentos Herbarios Chinos/química , Grafito , Óxidos , Medicamentos sin Prescripción/química , Extracción en Fase Sólida , JeringasRESUMEN
Relaxation and backwashing have become an integral part of membrane bioreactor (MBR) operations for fouling control. This study was carried out on real municipal wastewater to evaluate the influence of different operational strategies on membrane fouling at equivalent water yield. Four relaxation modes (MBR10+0, MBR10+1, MBR10+1.5 and MBR10+2) were tested to analyze membrane fouling behavior. For the optimization of relaxation modes, fouling rate in terms of trans-membrane pressure, hydraulic resistances and characteristics of fouling fractions were analyzed. It has been observed that cake layer resistance was minimum in MBR10+1.5 but pore blockage resistance was increased in all relaxation modes. Moreover, high instantaneous flux contributed significantly to fouling rate at the initial stage of MBR operations. Relaxation modes were also efficient in removing irreversible fouling to some extent. Under all relaxation modes, COD removal efficiency ranged from 92 to 96.5%. Ammonium and TP removal were on the lower side due to the short solids and hydraulic retention time.
Asunto(s)
Reactores Biológicos/normas , Membranas Artificiales , Aguas Residuales , Compuestos de Amonio/aislamiento & purificación , Purificación del Agua/métodosRESUMEN
Wastewaters contaminated by both selenium and ammonium need to be treated prior to discharge into natural water bodies, but there are no studies on the simultaneous removal of selenium and ammonium. A sequencing batch reactor (SBR) was inoculated with activated sludge and operated for 90days. The highest ammonium removal efficiency achieved was 98%, while the total nitrogen removal was 75%. Nearly a complete chemical oxygen demand removal efficiency was attained after 16days of operation, whereas complete selenate removal was achieved only after 66days. The highest total Se removal efficiency was 97%. Batch experiments showed that the total Se in the aqueous phase decreased by 21% with increasing initial ammonium concentration from 50 to 100mgL-1. This study showed that SBR can remove both selenate and ammonium via, respectively, bioreduction and partial nitrification-denitrification and thus offer possibilities for treating selenium and ammonium contaminated effluents.
Asunto(s)
Compuestos de Amonio/aislamiento & purificación , Técnicas de Cultivo Celular por Lotes/métodos , Reactores Biológicos/microbiología , Ácido Selénico/aislamiento & purificación , Aguas del Alcantarillado/microbiología , Biodegradación Ambiental , Análisis de la Demanda Biológica de Oxígeno , Nitratos/aislamiento & purificación , Nitritos/aislamiento & purificación , Nitrógeno/aislamiento & purificación , Selenio/aislamiento & purificación , Factores de TiempoRESUMEN
Digested piggery wastewater(DPW) contains high concentrations of nitrogen and phosphorus which could be used as a cost-effective culture medium for Spirulina platensis. However, Spirulina platensis would be limited by many factors in the complex composition of DPW, especially the high concentration of ammonium. In this paper, a traditional sequencing batch reactor(SBR) was used to remove these inhibitors in DPW. The retention of nitrate and nitrite in the effluent, which was used as nitrogen source for cultivating Spirulina platensis, was studied at different ratios of chemical oxygen demand(COD) to total nitrogen(TN) in the influent. By comparing the growth of Spirulina platensis in the related effluents, the operation condition of SBR was optimized. The lab-scale cultivation results showed that Spirulina platensis possessed a high biomass yield of 0.084 g·(L·d)-1 in the effluent when the COD/TN ratio of SBR influent was 3.0. In particular, the concentrations of ammonium, nitrate and nitrite in the effluent were 51.2 mg·L-1, 91.6 mg·L-1and 213.1 mg·L-1, respectively. Furthermore, the aforementioned effluent was also used to culture Spirulina platensis in a 120 L outdoor raceway pond, and the growth rate of Spirulina platensis reached(0.075±0.003)g·(L·d)-1 after 10-day culture. The protein content of Spirulina platensis was approximately 60% and the removal efficiency of ammonium was 99%. This study provides an alternative method for the utilization of DPW.
Asunto(s)
Reactores Biológicos , Nitrógeno/aislamiento & purificación , Fósforo/aislamiento & purificación , Spirulina/crecimiento & desarrollo , Eliminación de Residuos Líquidos/métodos , Compuestos de Amonio/aislamiento & purificación , Animales , Análisis de la Demanda Biológica de Oxígeno , Nitratos/aislamiento & purificación , Nitritos/aislamiento & purificación , Porcinos , Aguas ResidualesRESUMEN
In this study, the combination treatment of NaOH and Mg(OH)2 was applied to anaerobic digestion of waste activated sludge (WAS) for simultaneously enhancement of volatile fatty acids (VFAs) production, nutrients removal and sludge dewaterability. The maximum VFAs production (461mg COD/g VSS) was obtained at the NaOH/Mg(OH)2 ratio of 75:25, which was much higher than that of the blank or sole NaOH. Moreover, nutrients removal and sludge dewaterability were improved by the combined using of NaOH and Mg(OH)2. Mechanism investigations revealed that the presence of Mg(OH)2 could maintain alkaline environment, which contributed to inhibit the activity of methanogens. Also, the bridging between Mg(2+) and extracellular polymeric substances (EPS) plays an important role in the solubilization and dewatering of sludge. High-throughput sequencing analysis demonstrated that the abundance of bacteria involved in sludge hydrolysis and VFAs accumulation was greatly enriched with the mixtures of NaOH and Mg(OH)2.
Asunto(s)
Hidróxido de Magnesio/farmacología , Aguas del Alcantarillado/microbiología , Hidróxido de Sodio/farmacología , Residuos , Compuestos de Amonio/aislamiento & purificación , Anaerobiosis/efectos de los fármacos , Bacterias/efectos de los fármacos , Bacterias/metabolismo , Análisis de la Demanda Biológica de Oxígeno , Biopolímeros/química , Ácidos Grasos Volátiles/biosíntesis , Concentración de Iones de Hidrógeno , Fósforo/aislamiento & purificación , Solubilidad , Electricidad Estática , Aguas Residuales/microbiología , Agua , Purificación del AguaRESUMEN
In order to improve nitrogen removal for rural wastewater, a novel two-stage hybrid system, consisting of a vertical flow trickling filter (VFTF) and a horizontal flow multi-soil-layering (HFMSL) bioreactor was developed. The performance of the apparatus was observed under various carbon-nitrogen ratios and water spraying frequencies separately. The maximum removal efficiency of total nitrogen (TN) for the hybrid system was 92.8% while the removal rates of CODCr, ammonium (NH4(+)-N), and total phosphorus (TP) were 94.1%, 96.1%, 92.0% respectively, and the corresponding effluent concentrations were 3.61, 21.20, 1.91, and 0.33 mg L(-1). The horizontal flow mode for MSL led the system to denitrifying satisfactorily as it ensured relatively long hydraulic retention time (HRT), ideal anoxic condition and adequate organic substrates supply. Also, higher water spraying frequency benefited intermittent feeding system for pollutants removal. Shock loading test indicated that the hybrid system could operate well even at hydraulic shock loadings.
Asunto(s)
Reactores Biológicos , Filtración/instrumentación , Reología , Suelo , Aguas Residuales/análisis , Purificación del Agua/instrumentación , Purificación del Agua/métodos , Compuestos de Amonio/aislamiento & purificación , Análisis de la Demanda Biológica de Oxígeno , Carbono/análisis , Desnitrificación , Nitrificación , Nitrógeno/análisis , Fósforo/aislamiento & purificación , Reproducibilidad de los Resultados , Población Rural , Contaminantes Químicos del Agua/aislamiento & purificaciónRESUMEN
The performance of a BAF system configuring simultaneous chemical phosphorus precipitation in the pre-denitrification stage was examined using a continuously operated setup to treat real domestic wastewater. The effects of using no chemical, dosing sole Fe(2+), and dosing combined Fe(2+), PAM, and NaHCO3 in the pre-denitrification tank were assessed by monitoring COD, nitrogen, and phosphorus removal and hydraulic headloss development in the BAF column. Though dosing sole Fe(2+) significantly enhanced phosphorus removal, it would consume alkalinity through hydrolysis and form smaller-sized sludge flocs in the pre-denitrification tank, and hence resulted in affected NH4(+)-N, insoluble COD, and SS removal in the BAF. Dosing combined Fe(2+), PAM, and NaHCO3 can enhance sludge flocculation to form larger flocs and compensate alkalinity consumption. It exhibited sound performance on COD, nitrogen, and phosphorus removal, and led to less frequent BAF backwashing by slowing clogging development in the BAF filter layer.
Asunto(s)
Desnitrificación , Filtración/instrumentación , Fósforo/aislamiento & purificación , Contaminantes Químicos del Agua/aislamiento & purificación , Aerobiosis , Compuestos de Amonio/aislamiento & purificación , Biodegradación Ambiental , Análisis de la Demanda Biológica de Oxígeno , Precipitación Química , Concentración de Iones de Hidrógeno , Nitrógeno/aislamiento & purificación , Solubilidad , Aguas ResidualesRESUMEN
The impact of carbon source variation on the physical and chemical characteristics of aerobic granular sludge and its biological nutrient (nitrogen and phosphorus) removal performance was investigated. Two identical sequencing batch reactors, R1 and R2, were set up. Granular biomass was cultivated to maturity using acetate-based synthetic wastewater. After mature granules in both reactors with simultaneous chemical oxygen demand (COD), ammonium and phosphorus removal capability were achieved, the feed of R2 was changed to municipal wastewater and R1 was continued on synthetic feed as control. Biological phosphorus removal was completely inhibited in R2 due to lack of readily biodegradable COD; however, the biomass maintained high ammonium and COD removal efficiencies. The disintegration of the granules in R2 occurred during the first two weeks after the change of feed, but it did not have significant impacts on settling properties of the sludge. Re-granulation of the biomass in R2 was then observed within 30 d after granules' disintegration when the biomass acclimated to the new substrate. The granular biomass in R1 and R2 maintained a Sludge Volume Index close to 60 and 47 mL g(-1), respectively, during the experimental period. It was concluded that changing the carbon source from readily biodegradable acetate to the more complex ones present in municipal wastewater did not have significant impacts on aerobic granular sludge characteristics; it particularly did not affect its settling properties. However, sufficient readily biodegradable carbon would have to be provided to maintain simultaneous biological nitrate and phosphorus removal.
Asunto(s)
Carbono/química , Aguas del Alcantarillado/análisis , Aguas del Alcantarillado/microbiología , Eliminación de Residuos Líquidos/métodos , Aerobiosis , Compuestos de Amonio/aislamiento & purificación , Análisis de la Demanda Biológica de Oxígeno , Biomasa , Reactores Biológicos , Nitrógeno/aislamiento & purificación , Fósforo/aislamiento & purificaciónRESUMEN
An ozone/ultrasound lysis-cryptic growth technology combining a continuous flow anaerobic-anoxic-microaerobic-aerobic (AAMA+O3/US) system was investigated. Techno-economic evaluation and sludge lyses return ratio (r) optimization of this AAMA+O3/US system were systematically and comprehensively discussed. Economic assessment demonstrated that this AAMA+O3/US system with r of 30% (AAMA+O3/US2# system) was more economically feasible that can give a 14.04% saving of costs. In addition to economic benefits, a 55.08% reduction in sludge production, and respective 21.17% and 5.45% increases in TN and TP removal efficiencies were observed in this AAMA+O3/US2# system. Considering the process performances and economic benefits, r of 30% in AAMA+O3/US2# system was recommended. Excitation-emission matrix and Fourier transform infrared spectra analyses also proved that less refractory soluble microbial products were generated from AAMA+O3/US2# system. Improvement in 2,3,5-triphenyltetrazolium chloride electron transport system (TTC-ETS) activity in AAMA+O3/US2# further indicated that a lower sludge lyses return ratio stimulated the microbial activity.
Asunto(s)
Compuestos Orgánicos/aislamiento & purificación , Ozono/química , Aguas del Alcantarillado/química , Ultrasonido/métodos , Eliminación de Residuos Líquidos/economía , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/aislamiento & purificación , Aerobiosis , Compuestos de Amonio/aislamiento & purificación , Anaerobiosis , Biodegradación Ambiental , Análisis de la Demanda Biológica de Oxígeno , Transporte de Electrón , Nitrógeno/aislamiento & purificación , Fósforo/aislamiento & purificación , Espectrometría de Fluorescencia , Espectroscopía Infrarroja por Transformada de Fourier , Sales de Tetrazolio/química , Factores de TiempoRESUMEN
Magnesium ammonium phosphate (MAP) precipitation was introduced to remove ammonium nitrogen (NH4(+)-N) in autothermal thermophilic aerobic digestion (ATAD) in this study by addition of MgCl2 · 6H2O and NaH2PO4 · 2H2O. The results showed that the lowest NH4(+)-N concentration was found in the D2 digester after 2nd day dosing treatment and 38.12% of VS removal efficiency was obtained after 15 days ATAD treatment. Sludge stabilization was achieved in the D2 digester 6 days earlier than the non-dosing digester when 8.7 g/L MgCl2 · 6H2O and 6.7 g/L NaH2PO4 · 2H2O were added into the digester. Furthermore, the highest VS removal efficiency of 40.03% was observed after 21 days digestion in D2 digesters. Therefore, MAP precipitation was an effective method for the ammonium nitrogen disinhibition when 8.7 g/L MgCl2 · 6H2O and 6.7 g/L NaH2PO4 · 2H2O were added into on the 2nd day after the digester startup.
Asunto(s)
Compuestos de Amonio/aislamiento & purificación , Precipitación Química , Nitrógeno/aislamiento & purificación , Eliminación de Residuos/métodos , Aguas del Alcantarillado/química , Temperatura , Adenosina Trifosfato/metabolismo , Aerobiosis , Bacterias/metabolismo , Biodegradación Ambiental , Análisis de la Demanda Biológica de Oxígeno , Concentración de Iones de Hidrógeno , Oxígeno/metabolismo , Fósforo/aislamiento & purificación , Aguas del Alcantarillado/microbiología , VolatilizaciónRESUMEN
In this study, sequencing batch reactor (SBR) with an anaerobic/aerobic/anoxic operating mode was used to culture granular sludge. Optimal adjustment of cycle duration was achieved by the direction ofpH, oxidation reduction potential and dissolved oxygen parameters. The results showed that the treating efficiency was significantly improved as the cycle was shortened from 450 to 360 min and further to 200 min. Nitrogen and phosphorus removal were nearly quantitative after 50 days operation and maintained stable to the end of the study period. The typical cycle tests revealed that simultaneous denitrification and phosphorus removal occurred when aerobic granules were gradually formed. The nitrite effect tests showed that less than 4.8 mg N/L of the nitrite could enhance superficial specific aerobic phosphate uptake rate (SAPUR) under aerobic condition, indicating that the traditional method to evaluate the capability of total phosphate-accumulating organisms (PAOs) was inaccurate. Additionally, a high level of nitrite was detrimental to PAOs. A novel method was developed to determine the activity of each kind of PAOs and other denitrifying organisms. The results showed that (1) nitrate, besides nitrite, could also enhance SAPUR and (2) aerobic granular sludge could perform denitrification even when phosphate was not supplied under anoxic condition, suggesting that other denitrifying organisms besides denitrifying phosphate-accumulating organisms also contributed to denitrification.
Asunto(s)
Compuestos de Amonio/aislamiento & purificación , Reactores Biológicos/microbiología , Nitritos/metabolismo , Fósforo/aislamiento & purificación , Aerobiosis , Compuestos de Amonio/metabolismo , Anaerobiosis , Carbono/aislamiento & purificación , Fósforo/metabolismo , Aguas del Alcantarillado/microbiologíaRESUMEN
Microbial electrolysis cells (MECs) can be used to simultaneously convert wastewater organics to hydrogen and precipitate struvite, but scale formation at the cathode surface can block catalytic active sites and limit extended operation. To promote bulk phase struvite precipitation and minimize cathode scaling, a two-chamber MEC was designed with a fluidized bed to produce suspended particles and inhibit scale formation on the cathode surface. MEC operation elevated the cathode pH to between 8.3 and 8.7 under continuous flow conditions. Soluble phosphorus removal using digester effluent ranged from 70 to 85% with current generation, compared to 10-20% for the control (open circuit conditions). At low current densities (≤2 mA/m(2)), scouring of the cathode by fluidized particles prevented scale accumulation over a period of 8 days. There was nearly identical removal of soluble phosphorus and magnesium from solution, and an equimolar composition in the collected solids, supporting phosphorus removal by struvite formation. At an applied voltage of 1.0 V, energy consumption from the power supply and pumping (0.2 Wh/L, 7.5 Wh/g-P) was significantly less than that needed by other struvite formation methods based on pH adjustment such as aeration and NaOH addition. In the anode chamber, current generation led to COD oxidation (1.1-2.1 g-COD/L-d) and ammonium removal (7-12 mM) from digestate amended with 1 g/L of sodium acetate. These results indicate that a fluidized bed cathode MEC is a promising method of sustainable electrochemical nutrient and energy recovery method for nutrient rich wastewaters.
Asunto(s)
Fuentes de Energía Bioeléctrica , Técnicas Electroquímicas/métodos , Electrólisis , Compuestos de Magnesio/aislamiento & purificación , Fosfatos/aislamiento & purificación , Compuestos de Amonio/aislamiento & purificación , Biodegradación Ambiental , Análisis de la Demanda Biológica de Oxígeno , Carbonato de Calcio/aislamiento & purificación , Precipitación Química , Electricidad , Electrodos , Electrólitos/química , Iones , Microscopía Electrónica de Rastreo , Modelos Teóricos , Fósforo/aislamiento & purificación , Solubilidad , Soluciones , Estruvita , Eliminación de Residuos LíquidosRESUMEN
To enhance the denitrification performance of soil infiltration, a soil infiltration system incorporated with sulfur-utilizing autotrophic denitrification (SISSAD) for domestic wastewater treatment was developed, and the SISSAD performance was evaluated using synthetic domestic wastewater in this study. The aerobic respiration and nitrification were mainly taken place in the upper aerobic stage (AES), removed 88.44% COD and 89.99% NH4(+)-N. Moreover, autotrophic denitrification occurred in the bottom anaerobic stage (ANS), using the CO2 produced from AES as inorganic carbon source. Results demonstrated that the SISSAD showed a remarkable performance on COD removal efficiency of 95.09%, 84.86% for NO3(-)-N, 95.25% for NH4(+)-N and 93.15% for TP. This research revealed the developed system exhibits a promising application prospect for domestic wastewater in the future.
Asunto(s)
Procesos Autotróficos , Desnitrificación , Suelo/química , Azufre/metabolismo , Aguas Residuales/microbiología , Purificación del Agua/métodos , Compuestos de Amonio/aislamiento & purificación , Biodegradación Ambiental , Análisis de la Demanda Biológica de Oxígeno , Reactores Biológicos/microbiología , Concentración de Iones de Hidrógeno , Nitratos/aislamiento & purificación , Nitritos/aislamiento & purificación , Nitrógeno/aislamiento & purificación , Fósforo/aislamiento & purificación , Sulfatos/aislamiento & purificación , Purificación del Agua/instrumentaciónRESUMEN
In the view of limited phosphorous resources and tightened discharge regulations, the recovery of phosphate and nitrate from wastewater is of great interest. Here, the integration of microalgae into wastewater treatment processes is a promising approach. A prototype-scale Twin-Layer photobioreactor immobilizing the green alga Halochlorella rubescens on vertical sheet-like surfaces was constructed and operated using primary and secondary municipal wastewater. The process was not impaired by suspended solids, bacteria or loss of algal biomass by leaching. The average areal microalgal growth was 6.3 gm(-2) d(-1). After treatment, P and N concentrations in the effluents could efficiently be reduced by 70-99%, depending on element and type of wastewater. Mean effluent values of ⩽ 1.0mg L(-1)P and 1.3 mg L(-1)N met the legal discharge limits of the European Water Framework Directive and show a potential to comply with upcoming, more stringent legislation.
Asunto(s)
Ciudades , Microalgas/metabolismo , Nitrógeno/aislamiento & purificación , Fósforo/aislamiento & purificación , Fotobiorreactores/microbiología , Aguas Residuales/química , Purificación del Agua/instrumentación , Compuestos de Amonio/aislamiento & purificación , Biodegradación Ambiental , Biomasa , Células Inmovilizadas/metabolismo , Alemania , Microalgas/citología , Nitratos/aislamiento & purificación , Fosfatos/aislamiento & purificación , Aguas Residuales/microbiología , Contaminantes Químicos del Agua/aislamiento & purificaciónRESUMEN
A hybrid membrane bioreactor (HMBR) was developed, by adding biofilm support media into a conventional membrane bioreactor (CMBR), and operated in parallel with a CMBR. Results showed that effluent quality was significantly better with the HMBR. The removal efficiencies of COD, BOD5, NH4(+)-N and TN with the HMBR were 84%, 98%, 97% and 75%, respectively, as compared to 80%, 96%, 93% and 38% with the CMBR. There were no differences in phosphorus removal. The membrane fouling rate in the HMBR was on average only 57% of that in the CMBR. The lower concentration of colloidal biopolymer clusters in the HMBR sludge, probably due to their retention by the biofilm, could be partially responsible for this difference. Filterability and settleability of the sludge were also better in the HMBR. Consequently, it is concluded that the addition of fixed support media for biofilm growth can improve the performance of CMBRs.
Asunto(s)
Reactores Biológicos , Membranas Artificiales , Aguas Residuales/microbiología , Purificación del Agua/instrumentación , Purificación del Agua/métodos , Compuestos de Amonio/aislamiento & purificación , Biodegradación Ambiental , Análisis de la Demanda Biológica de Oxígeno , Nitrógeno/aislamiento & purificación , Compuestos Orgánicos/aislamiento & purificación , Fósforo/aislamiento & purificación , Proyectos Piloto , Presión , Aguas del Alcantarillado/químicaRESUMEN
The organics and nutrients in industrial and domestic wastewater are increasingly being regarded as a valuable resource for energy and nutrient recovery. Emerging concepts to redesign wastewater treatment as resource recovery systems include the use of different bacteria and algae to partition carbon and nutrients to the particulate phase through assimilation or bio-accumulation. This study evaluates the use of purple phototrophic bacteria (PPB) (also known as purple non-sulphur bacteria or PNSB) for such a biological concentration process through a series of batch tests. The key objectives are to (a) demonstrate consistent selection and enrichment of PPB using infrared light in a non-sterile medium, and (b) achieve effective partitioning of soluble organics, ammonium and phosphate into the PPB culture. PPB were successfully enriched from pre-settled domestic wastewater within 2-3 days and identified as members of the order Rhodobacterales. Under anaerobic conditions with infrared irradiation the enrichment culture was able to simultaneously remove COD (63 ± 5%), NH4-N (99.6%-0.12 ± 0.03 mgN L(-1)) and PO4-P (88%-0.8 ± 0.6 mgP L(-1)) from primary settled domestic wastewater in 24 h. In this experiment, acetate was added as an additional carbon source to demonstrate the maximal nitrogen and phosphorous elimination potential. Almost all the COD removed was assimilated into biomass rather than oxidised to CO2, with the total COD actually increasing during the batch experiments due to phototrophic synthesis. NH4-N and PO4-P were also assimilated by the biomass rather than removed through destructive oxidation or accumulation. The process offers the opportunity to concentrate organics and macronutrients from wastewater in one solids stream that can be anaerobically digested to generate energy and recover nutrients from the concentrated digestate. Technical challenges include the design of a continuous reactor system, as well as efficient delivery of electrons, either through light or chemical sources.
Asunto(s)
Nitrógeno/aislamiento & purificación , Fósforo/aislamiento & purificación , Procesos Fototróficos , Proteobacteria/metabolismo , Aguas Residuales/microbiología , Compuestos de Amonio/aislamiento & purificación , Técnicas de Cultivo Celular por Lotes , Biodegradación Ambiental/efectos de la radiación , Análisis de la Demanda Biológica de Oxígeno , Color , Hibridación Fluorescente in Situ , Rayos Infrarrojos , Fosfatos/aislamiento & purificación , Procesos Fototróficos/efectos de la radiación , Proteobacteria/efectos de la radiaciónRESUMEN
Proper and effective management of soil nutrients requires assessment of their variability at the field scale. We compare the effects of lime amendment rate on the spatial variability of three macronutrient forms (NH4 (+)-N, Olsen P, and Mehlich-1 K) in a paddy soil at three different dates during the growth period of a rice crop. The field work was carried out near Corrientes, Argentina. Lime treatments were 0, 625, and 1250 kg ha(-1) dolomite, and each liming dose was applied to a 1.7 ha field. Ninety-three soil samples per treatment were first collected in aerobic conditions and then two more times after flooding, at bunch formation and flowering. Soil NH4 (+)-N increased along time, whereas P was highest at bunch formation and K steadily decreased along the rice growth period. Dolomite addition increased macronutrient availability at the first and second samplings, but its effects at the third sampling depended on the element. The three soil nutrients analyzed displayed strong patterns of spatial dependence for the three lime treatments and at the three periods studied. The areas with relative high or low macronutrient concentrations within each field were not stable throughout the rice growth period. Seasonality in the spatial distribution of macronutrients may be of agronomic value for site specific management.