Full-scale demonstration of biological nutrient removal in a single tank SBR process

Complete biological nutrient removal (BNR) in a single tank, sequencing batch reactor (SBR) process, is demonstrated here at full-scale on a typical domestic wastewater. The unique feature of the UniFed process is the introduction of the influent into the settled sludge blanket during the settling and decant periods of the SBR operation. This achieves suitable conditions for denitrification and anaerobic phosphate release which is critical to successful biological phosphorus removal, It also achieves a selector effect, which helps in generating a compact, well settling biomass in the reactor. The results of this demonstration show that it is possible to achieve well over 90% removal of GOD, nitrogen and phosphorus in such a process. Effluent quality achieved over a six-month operating period directly after commissioning was: 29 mg/l GOD, 0.5 mg/l NH4-N, 1.5 mg/l NOx-N and 1.5 mg/l PO4-P (50%-iles of daily samples). During an 8-day, intensive sampling period, the effluent BOD5 was

Biological nutrient removal in SBR technology: from floccular to granular sludge

Biological nutrient removal has been studied and applied for decades in order to remove nitrogen and phosphorus from wastewater. However, more anthropogenic uses and the continued demand for water have forced the facilities to operate at their maximum capacity. Therefore, the goal of this thesis is to obtain more compact systems for nutrient removal from domestic wastewater. In this sense, optimization and long-term stabilization of high volume exchange ratios reactors, treating higher volumes of wastewater, have been investigated. With the same target, aerobic granular sludge was proposed as a reliable alternative to reduce space and increase loading rates in treatment plants. However, the low organic loading rate from low-strength influents (less than 1 Kg COD•m-3d-1) results in slower granular formation and a longer time to reach a steady state. Because of that, different methodologies and operational conditions were investigated in order to enhance granulation and nutrient removal from domestic wastewater.

Operation and control of SBR processes for enhanced biological nutrient removal from wastewater

In the last decades, the awareness of environmental issues has increased in society considerably. There is an increasing need to improve the effluent quality of domestic wastewater treatment processes. This thesis describes the application of the Sequencing Batch Reactor (SBR) technology for Biological Nutrient Removal (BNR) from the wastewater. In particular, the work presented evolves from the nitrogen removal to the biological nutrient removal (i.e. nitrogen plus phosphorous removal) with special attention to the operational strategy design, the identification of possible reactor cycle controls or the influent composition related to the process efficiency. In such sense, also the use of ethanol as an external carbon (when low influent Carbon:Phosphorus (C:P) or Carbon:Nitrogen (C:N) ratios are presented) are studied as an alternative to maintain the BNR efficiency.

SBR technology for wastewater treatment: suitable operational conditions for a nutrient removal

Actualment, la legislació ambiental ha esdevingut més restrictiva pel que fa a la descàrrega d'aigües residuals amb nutrients, especialment en les anomenades àrees sensibles o zones vulnerables. Arran d'aquest fet, s'ha estimulat el coneixement, desenvolupament i millora dels processos d'eliminació de nutrients. El Reactor Discontinu Seqüencial (RDS) o Sequencing Batch Reactor (SBR) en anglès, és un sistema de tractament de fangs actius que opera mitjançant un procediment d'omplerta-buidat. En aquest tipus de reactors, l'aigua residual és addicionada en un sol reactor que treballa per càrregues repetint un cicle (seqüència) al llarg del temps. Una de les característiques dels SBR és que totes les diferents operacions (omplerta, reacció, sedimentació i buidat) es donen en un mateix reactor. La tecnologia SBR no és nova d'ara. El fet, és que va aparèixer abans que els sistema de tractament continu de fangs actius. El precursor dels SBR va ser un sistema d'omplerta-buidat que operava en discontinu. Entre els anys 1914 i 1920, varen sorgir certes dificultats moltes d'elles a nivell d'operació (vàlvules, canvis el cabal d'un reactor a un altre, elevat temps d'atenció per l'operari...) per aquests reactors. Però no va ser fins a finals de la dècada dels '50 principis del '60, amb el desenvolupament de nous equipaments i noves tecnologies, quan va tornar a ressorgir l'interès pels SBRs. Importants millores en el camp del subministrament d'aire (vàlvules motoritzades o d'acció pneumàtica) i en el de control (sondes de nivell, mesuradors de cabal, temporitzadors automàtics, microprocessadors) han permès que avui en dia els SBRs competeixin amb els sistemes convencional de fangs actius. L'objectiu de la present tesi és la identificació de les condicions d'operació adequades per un cicle segons el tipus d'aigua residual a l'entrada, les necessitats del tractament i la qualitat desitjada de la sortida utilitzant la tecnologia SBR. Aquestes tres característiques, l'aigua a tractar, les necessitats del tractament i la qualitat final desitjada determinen en gran mesura el tractament a realitzar. Així doncs, per tal d'adequar el tractament a cada tipus d'aigua residual i les seves necessitats, han estat estudiats diferents estratègies d'alimentació. El seguiment del procés es realitza mitjançant mesures on-line de pH, OD i RedOx, els canvis de les quals donen informació sobre l'estat del procés. Alhora un altre paràmetre que es pot calcular a partir de l'oxigen dissolt és la OUR que és una dada complementària als paràmetres esmentats. S'han avaluat les condicions d'operació per eliminar nitrogen d'una aigua residual sintètica utilitzant una estratègia d'alimentació esglaonada, a través de l'estudi de l'efecte del nombre d'alimentacions, la definició de la llargada i el número de fases per cicle, i la identificació dels punts crítics seguint les sondes de pH, OD i RedOx. S'ha aplicat l'estratègia d'alimentació esglaonada a dues aigües residuals diferents: una procedent d'una indústria tèxtil i l'altra, dels lixiviats d'un abocador. En ambdues aigües residuals es va estudiar l'eficiència del procés a partir de les condicions d'operació i de la velocitat del consum d'oxigen. Mentre que en l'aigua residual tèxtil el principal objectiu era eliminar matèria orgànica, en l'aigua procedent dels lixiviats d'abocador era eliminar matèria orgànica i nitrogen. S'han avaluat les condicions d'operació per eliminar nitrogen i fòsfor d'una aigua residual urbana utilitzant una estratègia d'alimentació esglaonada, a través de la definició del número i la llargada de les fases per cicle, i la identificació dels punts crítics seguint les sondes de pH, OD i RedOx. S'ha analitzat la influència del pH i la font de carboni per tal d'eliminar fòsfor d'una aigua sintètica a partir de l'estudi de l'increment de pH a dos reactors amb diferents fonts de carboni i l'estudi de l'efecte de canviar la font de carboni. Tal i com es pot veure al llarg de la tesi, on s'han tractat diferents aigües residuals per a diferents necessitats, un dels avantatges més importants d'un SBR és la seva flexibilitat.

Algal wastewater treatment and biomass producing potential: nutrient removal efficiency and cell physiological responses

Microalgae are sun - light cell factories that convert carbon dioxide to biofuels, foods, feeds, and other bioproducts. The concept of microalgae cultivation as an integrated system in wastewater treatment has optimized the potential of the microalgae - based biofuel production. These microorganisms contains lipids, polysaccharides, proteins, pigments and other cell compounds, and their biomass can provide different kinds of biofuels such as biodiesel, biomethane and ethanol. The algal biomass application strongly depends on the cell composition and the production of biofuels appears to be economically convenient only in conjunction with wastewater treatment. The aim of this research thesis was to investigate a biological wastewater system on a laboratory scale growing a newly isolated freshwater microalgae, Desmodesmus communis, in effluents generated by a local wastewater reclamation facility in Cesena (Emilia Romagna, Italy) in batch and semi - continuous cultures. This work showed the potential utilization of this microorganism in an algae - based wastewater treatment; Desmodesmus communis had a great capacity to grow in the wastewater, competing with other microorganisms naturally present and adapting to various environmental conditions such as different irradiance levels and nutrient concentrations. The nutrient removal efficiency was characterized at different hydraulic retention times as well as the algal growth rate and biomass composition in terms of proteins, polysaccharides, total lipids and total fatty acids (TFAs) which are considered the substrate for biodiesel production. The biochemical analyses were coupled with the biomass elemental analysis which specified the amount of carbon and nitrogen in the algal biomass. Furthermore photosynthetic investigations were carried out to better correlate the environmental conditions with the physiology responses of the cells and consequently get more information to optimize the growth rate and the increase of TFAs and C/N ratio, cellular compounds and biomass parameter which are fundamental in the biomass energy recovery.

High rate nutrient removal for combined sewer overflows : bench scale and demonstration scale studies /

Mode of access: Internet.

Two-stage thermophilic-mesophilic anaerobic digestion of waste activated sludge-from a biological nutrient removal plant

A two-stage thermophilic-mesophilic anaerobic digestion pilot-plant was operated solely on waste activated sludge (WAS) from a biological nutrient removal (BNR) plant. The first-stage thermophilic reactor (HRT 2 days) was operated at 47, 54 and 60 degrees C. The second-stage mesophilic digester (HRT 15 days) was held at a constant temperature of 36-37 degrees C. For comparison with a single-stage mesophilic process, the mesophilic digester was also operated separately with an HRT of 17 days and temperature of 36-37 degrees C. The results showed a truly thermophilic stage (60 degrees C) was essential to achieve good WAS degradation. The lower thermophilic temperatures examined did not offer advantages over single-stage mesophilic treatment in terms of COD and VS removal. At a thermophilic temperature of 60 degrees C, the plant achieved 35% VS reduction, representing a 46% increase compared to the single-stage mesophilic digester. This is a significant level of degradation which could make such a process viable in situations where there is no primary sludge generated. The fate of the biologically stored phosphorus in this BNR sludge was also investigated. Over 80% of the incoming phosphorus remained bound up with the solids and was not released into solution during the WAS digestion. Therefore only a small fraction of phosphorus would be recycled to the main treatment plant with the dewatering stream.

Predicting the effect of mixing on oxygen transfer and nutrient removal in activated sludge basins

Activated sludge basins (ASBs) are a key-step in wastewater treatment processes that are used to eliminate biodegradable pollution from the water discharged to the natural environment. Bacteria found in the activated sludge consume and assimilate nutrients such as carbon, nitrogen and phosphorous under specific environmental conditions. However, applying the appropriate agitation and aeration regimes to supply the environmental conditions to promote the growth of the bacteria is not easy. The agitation and aeration regimes that are applied to activated sludge basins have a strong influence on the efficacy of wastewater treatment processes. The major aims of agitation by submersible mixers are to improve the contact between biomass and wastewater and the prevention of biomass settling. They induce a horizontal flow in the oxidation ditch, which can be quantified by the mean horizontal velocity. Mean values of 0.3-0.35 m s-1 are recommended as a design criteria to ensure best conditions for mixing and aeration (Da Silva, 1994). To give circulation velocities of this order of magnitude, the positioning and types of mixers are chosen from the plant constructors' experience and the suppliers' data for the impellers. Some case studies of existing plants have shown that measured velocities were not in the range that was specified in the plant design. This illustrates that there is still a need for design and diagnosis approach to improve process reliability by eliminating or reducing the number of short circuits, dead zones, zones of inefficient mixing and poor aeration. The objective of the aeration is to facilitate the quick degradation of pollutants by bacterial growth. To achieve these objectives a wastewater treatment plant must be adequately aerated; thus resulting in 60-80% of all energetic consummation being dedicated to the aeration alone (Juspin and Vasel, 2000). An earlier study (Gillot et al., 1997) has illustrated the influence that hydrodynamics have on the aeration performance as measure by the oxygen transfer coefficient. Therefore, optimising the agitation and aeration systems can enhance the oxygen transfer coefficient and consequently reduce the operating costs of the wastewater treatment plant. It is critically important to correctly estimate the mass transfer coefficient as any errors could result in the simulations of biological activity not being physically representative. Therefore, the transfer process was rigorously examined in several different types of process equipment to determine the impact that different hydrodynamic regimes and liquid-side film transfer coefficients have on the gas phase and the mass transfer of oxygen. To model the biological activity occurring in ASBs, several generic biochemical reaction models have been developed to characterise different biochemical reaction processes that are known as Activated Sludge Models, ASM (Henze et al., 2000). The ASM1 protocol was selected to characterise the impact of aeration on the bacteria consuming and assimilating ammonia and nitrate in the wastewater. However, one drawback of ASM protocols is that the hydrodynamics are assumed to be uniform by the use of perfectly mixed, plug flow reactors or as a number of perfectly mixed reactors in series. This makes it very difficult to identify the influence of mixing and aeration on oxygen mass transfer and biological activity. Therefore, to account for the impact of local gas-liquid mixing regime on the biochemical activity Computational Fluid Dynamics (CFD) was used by applying the individual ASM1 reaction equations as the source terms to a number of scalar equations. Thus, the application of ASM1 to CFD (FLUENT) enabled the investigation of the oxygen transfer efficiency and the carbon & nitrogen biological removal in pilot (7.5 cubic metres) and plant scale (6000 cubic metres) ASBs. Both studies have been used to validate the effect that the hydrodynamic regime has on oxygen mass transfer (the circulation velocity and mass transfer coefficient) and the effect that this had on the biological activity on pollutants such as ammonia and nitrate (Cartland Glover et al., 2005). The work presented here is one part to of an overall approach for improving the understanding of ASBs and the impact that they have in terms of the hydraulic and biological performance on the overall wastewater treatment process. References CARTLAND GLOVER G., PRINTEMPS C., ESSEMIANI K., MEINHOLD J., (2005) Modelling of wastewater treatment plants ? How far shall we go with sophisticated modelling tools? 3rd IWA Leading-Edge Conference & Exhibition on Water and Wastewater Treatment Technologies, 6-8 June 2005, Sapporo, Japan DA SILVA G. (1994). Eléments d'optimisation du transfert d'oxygène par fines bulles et agitateur séparé en chenal d'oxydation. PhD Thesis. CEMAGREF Antony ? France. GILLOT S., DERONZIER G., HEDUIT A. (1997). Oxygen transfer under process conditions in an oxidation ditch equipped with fine bubble diffusers and slow speed mixers. WEFTEC, Chicago, USA. HENZE M., GUJER W., MINO T., van LOOSDRECHT M., (2000). Activated Sludge Models ASM1, ASM2, ASM2D and ASM3, Scientific and Technical Report No. 9. IWA Publishing, London, UK. JUSPIN H., VASEL J.-L. (2000). Influence of hydrodynamics on oxygen transfer in the activated sludge process. IWA, Paris - France.

Nitrogen removal in a sequencing batch biofilm reactor with liquid circulation: Effect of feed strategy and carbon source in the denitrifying step

Ammonium nitrogen removal from a synthetic wastewater by nitrification and denitrification processes were performed in a sequencing batch biofilm reactor containing immobilized biomass on polyurethane foam with circulation of the liquid-phase. It was analyzed the effect of four external carbon sources (ethanol, acetate, carbon synthetic medium and methanol) acting as electron donors in the denitrifying process. The experiments were conducted with intermittent aeration and operated at 30+/-1 degrees C in 8-h cycles. The synthetic wastewater (100 mgCOD/L and 50 mgNH(4)(+)-N/L) was added batch-wise, while the external carbon sources were added fed-batch-wise during the periods where aeration was suspended. Ammonium nitrogen removal efficiencies obtained were 95.7, 94.3 and 97.5% for ethanol, acetate and carbon synthetic medium, respectively. As to nitrite, nitrate and ammonium nitrogen effluent concentrations, the results obtained were, respectively: 0.1, 5.7 and 1.4 mg/L for ethanol; 0.2, 4.1 and 1.8 mg/L for acetate and 0.2, 6.7 and 0.8 for carbon synthetic medium. On the other hand using methanol, even at low concentrations (50% of the stoichiometric value calculated for complete denitrification), resulted in increasing accumulation of nitrate and ammonium nitrogen in the effluent over time.

Sustainability of Wood Productivity of Pinus TaedaBased on Nutrient Export and Stocks in the Biomass and in the Soil

ABSTRACT The impact of intensive management practices on the sustainability of forest production depends on maintenance of soil fertility. The contribution of forest residues and nutrient cycling in this process is critical. A 16-year-old stand of Pinus taeda in a Cambissolo Húmico Alumínico léptico (Humic Endo-lithic Dystrudept) in the south of Brazil was studied. A total of 10 trees were sampled distributed in five diameter classes according to diameter at breast height. The biomass of the needles, twigs, bark, wood, and roots was measured for each tree. In addition to plant biomass, accumulated plant litter was sampled, and soil samples were taken at three increments based on sampling depth: 0.00-0.20, 0.20-0.40, 0.40-0.60, 0.60-1.00, 1.00-1.40, 1.40-1.80, and 1.80-1.90 m. The quantity and concentration of nutrients, as well as mineralogical characteristics, were determined for each soil sample. Three scenarios of harvesting intensities were simulated: wood removal (A), wood and bark removal (B), and wood + bark + canopy removal (C). The sum of all biomass components was 313 Mg ha-1.The stocks of nutrients in the trees decreased in the order N>Ca>K>S>Mg>P. The mineralogy of the Cambissolo Húmico Alumínico léptico showed the predominance of quartz sand and small traces of vermiculite in the silt fraction. Clay is the main fraction that contributes to soil weathering, due to the transformation of illite-vermiculite, releasing K. The depletion of nutrients from the soil biomass was in the order: P>S>N>K>Mg>Ca. Phosphorus and S were the most limiting in scenario A due to their low stock in the soil. In scenario B, the number of forest rotations was limited by N, K, and S. Scenario C showed the greatest reduction in productivity, allowing only two rotations before P limitation. It is therefore apparent that there may be a difference of up to 30 years in the capacity of the soil to support a scenario such as A, with a low nutrient removal, compared to scenario C, with a high nutrient removal. Hence, the effect of different harvesting intensities on nutrient availability may jeopardize the sustainability of P. taeda in the short-term.

Removal of organic matter and nutrients from slaughterhouse wastewater by using Eichhornia crassipes and evaluation of the generated biomass composting

The objective of this research was to evaluate the performance of the aquatic macrophyte Eichhornia crassipes applied in situ in a slaughter house treatment system, located in the west of the Paraná state, Brazil, regarding the nutrients removal and organic matter. Moreover, it aimed to obtain data from the production, management and composting practices of the biomass generated in the system. During 11 months of macrophytes development, physic and chemical parameters were monitored and plant density was controlled by periodical removal of excess biomass, which was weekly monitored and it is expressed in kg of aquatic plant per m² covered area. The degradation of the macrophytes removed from the treatment system was evaluated at the pilot scale in eight composting piles of 0.60 m³ that underwent four different treatments and two repetitions: T1 - water hyacinth (Eichhornia crassipes); T2 - water hyacinth and swine excrement (7:1), T3 - water hyacinth, swine excrement and earth (7:1:0,67), and T4 - water hyacinth, swine excrement and cellulosic gut (7:1:0,67), for a period of 90 days. The results indicated maximum removal efficiencies of 77.2% for COD; 77.8% for BOD, 87.9% for total nitrogen, 47.5% for ammonia nitrogen and 38.9% for total phosphorus for a five-day retention time. For biomass stabilization by composting, considering the C:N ratio as an indicator of compost maturity, it was observed that treatment T4 resulted in the shortest stabilization period (60 days). No difference was verified in the biostabilization rates at 5% level by the F test.