5,999 research outputs found
The importance of pretreatment tailoring on the performance of ultrafiltration membranes to treat two-phase olive mill wastewater
In this work, the performance of an ultrafiltration (UF) membrane in the treatment of the effluents
by-produced by olive mills is addressed by applying different pretreatments on the raw effluents. By conducting
a photo-catalytic process (UV/TiO2 PC) after pH-temperature flocculation (pH-T F) higher threshold
flux values were observed for all feed stocks than by applying solely the pH-T F process, with an 18.8–34.2%
increment. In addition, the performance of the UF membrane was also improved in terms of rejection efficiency,
such that higher rejection values were yielded by the membrane for the organic pollutants (RCOD) by
48.5 vs. 39.9% and 53.4 vs. 42.0%. The UF membrane performance was also improved in terms of the volume
feed recovery factor (VFR), achieving up to 88.2 vs. 87.2% and 90.7 vs. 89.3%. Results in the same line were
also observed when the highly polluted olives oil washing wastewater raw stream was previously mixed with the
effluent stream coming from the washing of the olives. This permits the UF to permeate, achieving the standard
limits to reuse the purified effluent for irrigation purposes (COD values below 1000 mg·L−1), which makes the
treatment process cost-effective and results in making the olive oil production process environmentally friendly.En este estudio se aborda el rendimiento de una
membrana de ultrafiltración (UF) para el tratamiento de los efluentes generados por la industria oleícola, mediante
la aplicación de distintos pretratamientos. Tras aplicar un proceso fotocatalítico (UV/TiO2 PC) después
de una floculación pH-temperatura (pH-T F) se observaron flujos límite para todos los efluentes mayores que
tras la aplicación únicamente del proceso pH-T F, con incrementos del 18.8–34.2 %. Además, el rendimiento de
la membrana de UF mejoró en términos de eficiencia de rechazo, con mayores valores de rechazo respecto de
los contaminantes orgánicos (RCOD), 48.5 vs. 39.9 % y 53.4 vs. 42.0 %. El rendimiento de la membrana mejoró
también en términos de recuperación de volumen de alimentación (VRF), alcanzando hasta un 88.2 vs. 87.2 % y
90.7 vs. 89.3 %. Se observaron resultados en la misma línea cuando las aguas residuales del lavado del aceite,
altamente contaminadas, fueron previamente mezcladas con el efluente generado en el lavado de las aceitunas.
Esto permite que el permeado de la UF cumpla con los límites estándar para la utilización del efluente para riego
(valores de la DQO inferiores a 1000 mg L−1), favoreciendo la eficiencia económica del proceso de tratamiento
y permitiendo que el proceso de producción del aceite de oliva pueda ser respetuoso con el medio ambiente.The membrane pilot plant was constructed in the
framework of the European project PHOTOMEM
(contract no.FP7-SME-2011, grant 262470) and
revamped under the European project ETOILE (contract
no. FP7-SME-2007-1, grant 222331). Funding by the EC is gratefully acknowledged. The Spanish
Ministry of Science and Innovation is also gratefully
acknowledged for having funded the projects
CTQ2007-66178 and CTQ2010-21411, as well as the
University of Granada
About the limits of microfiltration for the purification of wastewaters
In the past, microfiltration was widely used as a
pretreatment step for wastewater stream purification
purposes. Experiences performed during the last years
shows that microfiltration fails to maintain its
performances for longer period of times. Many case studies
demonstrate that the adoption of microfiltration leads to
the failure of the overall process; the severe fouling of the
microfiltration membranes leads to high operating costs
with the consequence to make the treatment of the
wastewater economically unfeasible. The boundary flux
concept is a profitable tool to analyze fouling issues in
membrane processes. The boundary flux value separates an
operating region characterized by reversible fouling
formation from irreversible one. Boundary flux values are
not content, but function of time, as calculated by the subboundary
fouling rate value. The knowledge of both
parameters may fully describe the membrane performances
in sub-boundary operating regimes. Many times, for
wastewater purification purposes, ultrafiltration
membranes appear to be suits better to the needs, even they
exhibit lower permeate fluxes compared to microfiltration.
Key to this choice is that ultrafiltration appears to resist
better to fouling issues, with a limited reduction of the
performances as a function of time. In other words, it
appears that ultrafiltration exhibit higher boundary flux
values and lower sub-boundary fouling rates. In this work,
after a brief introduction to the boundary flux concept, for
many different wastewater streams (more than 20,
produced by the most relevant industries in food,
agriculture, manufacture, pharmaceutics), the boundary
flux and sub-boundary fouling rate values of different
microfiltration and ultrafiltration membranes will be
discussed and compared. The possibility to successfully
use microfiltration as a pretreatment step strongly depends
on the feedstock characteristics and, in detail, on the
particle size of the suspended matter. In most cases,
microfiltration demonstrates to be technically unsuitable
for pretreatment purposes of many wastewater streams; as
a consequence, the adoption of microfiltration pushes
operators to exceed boundary flux conditions, therefore
triggering severe fouling, that leads to economic
unfeasibility of the process in long terms
Chromium recovery by membranes for process reuse in the tannery industry
Leather tanning is a wide common industry all over the
world. In leather processing, water is one of the most
important medium, almost 40-45 L water kg-1 raw-hide or
skin is used by tanneries for processing finished leathers.
The composition of tannery wastewater presents
considerable dissimilarities in the concentration range of
pollutants both of inorganic (chlorides, with concentration
ranging from several hundred to over 10,000 mg L-1 Cl–;
sulphate (VI), ammonium ions and sulphide ions,
exhibiting concentration that ranges from tens to several
hundred mg L-1) and organic (the COD value is usually
several thousand mg L-1 O2). Throughout the years, many
conventional processes have been carried out to treat
wastewater from tannery industry: unfortunately, in this
case, biological treatment methods give rise to an
excessive production of sludge, whereas physical and
chemical methods are too expensive in terms of energy and
reagent costs. In this work, a membrane process based on
NF membrane modules was adopted to treat the tannery
feedstock after primary conventional treatment. In a first
step, the determination of all boundary flux parameters, in
order to inhibit severe fouling formation during operation,
were performed. After this, experimental work was carried
out to validate the approach. The target of water
purification was reached, that is the legal discharge to
municipal sewer system in Italy of 90% of the initial
wastewater stream volume. This allows having an
immediate cost saving of 21%. Moreover, the developed
process leads to a second benefit, that is the production of
5% of the initial volume as a highly chromium-rich
concentrate at no cost suitable to tannery process recycle
and reuse. In this case, cost saving rates exceeds 40%. At
the end, scale-up of the investigated process will be
discussed from technical and economic point of view
Comparison between refinement results of apatites from Celia mine (Murcia, Spain) using X-ray diffraction powder and single-crystal data
The results of crystal structure refinement of apatites, Ca5(PO4)3(OH,F,Cl), found in Celia mine (Murcia, Spain) using X-ray powder diffraction single crystal data are compared. According chemical and X-ray results these apatites are fluorapatites. Finally this study shows that the X-ray powder diffraction technique can be successfully applied in mineralogy to crystal structure studies with a precision probably sufficient for most purposes
Regarding the rejection performance of a polymeric reverse osmosis membrane for the final purification of two-phase olive mill effluents previously treated by an advanced oxidation process
In previous works on olive mill wastewater (OMW), secondary advanced oxidation treatment solved the problem related to the presence of phenolic compounds and considerable chemical oxygen demand. However, the effluent presented a significant salinity after this treatment. In this work, an adequate operation of a reverse osmosis (RO) membrane is addressed to ensure constant performance over a long period of time. In this paper, the effect of the operating parameters on the dynamic membrane rejection performance towards the target species was examined and discussed. Rejection efficiencies of all species were observed to follow a similar pattern, which consisted of slight initial improvement that further decreased over time. Rejection of both divalent ions remained constant at over 99% regardless of the operating conditions. Rejections were noticed to follow the order SO42- > Cl- > NO3- and Ca2+ > Mg2+> K+> Na+, as a rule. Divalent species were moderately more highly rejected than monovalent ones, in accordance with their higher charge and molecular size, and sulfate anions were consistently rejected by over 99%. Finally, the RO membrane exiting treated effluent was depleted of the high electro conductivity initially present (above 97% rejection), permitting its re-use as good quality irrigation water (below 1 mS/cm)
Tris(5-methyl-3-phenyl-1H-pyrazol-1-yl)methane
The first crystal structure of a second-generation tris(pyrazolyl)methane, namely the title compound, C31H28N6, is reported. The molecule exhibits a helical conformation with an average twist of 35.1°. In addition, there are C—H⋯π interactions of 3.202 (2) Å between the pyrazole C—H group and neighbouring phenyl groups
Sobre la eficiencia del rechazo de una membrana polimérica de ósmosis inversa para la purificación del agua residual de almazara de dos fases, previamente tratada mediante un proceso avanzado de oxidación
In previous works on olive mill wastewater (OMW), secondary advanced oxidation treatment solved the problem related to the presence of phenolic compounds and considerable chemical oxygen demand. However, the effluent presented a significant salinity after this treatment. In this work, an adequate operation of a reverse osmosis (RO) membrane is addressed to ensure constant performance over a long period of time. In this paper, the effect of the operating parameters on the dynamic membrane rejection performance towards the target species was examined and discussed. Rejection efficiencies of all species were observed to follow a similar pattern, which consisted of slight initial improvement that further decreased over time. Rejection of both divalent ions remained constant at over 99% regardless of the operating conditions. Rejections were noticed to follow the order SO42- > Cl- > NO3- and Ca2+ > Mg2+> K+> Na+, as a rule. Divalent species were moderately more highly rejected than monovalent ones, in accordance with their higher charge and molecular size, and sulfate anions were consistently rejected by over 99%. Finally, the RO membrane exiting treated effluent was depleted of the high electro conductivity initially present (above 97% rejection), permitting its re-use as good quality irrigation water (below 1 mS/cm).En trabajos previos con agua residual de almazara, se solucionó el problema en relación a la presencia de compuestos fenólicos y la considerable concentración de material orgánico. Sin embargo, el efluente presentaba una salinidad significativa tras éste. Este trabajo tiene por objetivo estudiar la adecuada operación de una membrana de ósmosis inversa (OI) para asegurar rendimientos constantes por largos períodos de tiempo de operación. Se examina y discute el efecto de los parámetros de operación en el rendimiento dinámico del rechazo de especies diana. Se observó que la eficiencia de rechazo de todas las especies siguió un patrón similar, consistente en una mejora inicial que posteriormente minoró con el tiempo de operación. El rechazo de iones divalentes se mantuvo constante sobre 99% independientemente de las condiciones de operación. La selectividad del rechazo siguió el orden SO42- > Cl- > NO3- y Ca2+ > Mg2+ > K+> Na+ en general. Las especies divalentes fueron moderadamente más rechazadas que las monovalentes, en concordancia con su mayor carga y tamaño molecular, y los iones sulfato fueron consistentemente rechazados al 99%. Finalmente, el efluente a la salida de la membrana de OI se encontraba exento de los altos valores de conductividad inicialmente presentes (rechazo superior al 97%), permitiendo su reutilización como agua de regadío de buena calidad (inferior a 1 mS/cm)
Recovery of iron after Fenton-like secondary treatment of olive mill wastewater by nano-filtration and low-pressure reverse osmosis membranes
In this work, the performances of novel nano-filtration (NF) and low-pressure reverse osmosis (RO) polymeric membranes were examined with the aim of recovering the iron used as catalyst in former secondary treatment based on the Fenton-like advanced oxidation of olive mill wastewater (OMW). Results highlight that both membranes exhibit a good performance towards the rejection of iron (99.1% for the NF membrane <em>vs.</em> 100% for the low-pressure RO membrane) in the secondary-treated OMW effluent, thus permitting the recovery of iron in the concentrate stream in order to recycle it back into the oxidation reactor to reduce catalyst consumption. Finally, the permeate streams could be re-used for irrigation. Major productivity was observed by the selected NF membrane, about 47.4 L/hm<sup>2</sup> upon 9 bar, whereas 30.9 L/hm<sup>2</sup> could be yielded with the RO membrane under an operating pressure of 8 bar. Moreover, a sensibly lower fouling index was measured on the NF membrane (0.0072 in contrast with 0.065), which ensures major steady-state performance on this membrane and a longer service lifetime. This also results in lower required membrane area and membrane plant over dimension (4 modules in case of RO operation whereas only 2 modules for NF).<br><br>En este trabajo, se examinó el rendimiento de membranas modernas de nanofiltración (NF) y ósmosis inversa (OI) poliméricas con el objetivo de recuperar el hierro utilizado como catalizador en un tratamiento secundario previo de agua residual oleícola (OMW) basado en oxidación avanzada tipo Fenton. Los resultados ponen de relieven que ambas membranas exhiben buen rendimiento en cuanto al rechazo de hierro (99.1 % para la membrana de NF vs. 100 % para la membrana de OI de bajas presiones) en el efluente oleícola tras tratamiento secundario, permitiendo en consecuencia la recuperación de hierro en la corriente de concentrado para su recirculación de nuevo al reactor de oxidación para reducir el consumo de catalizador. Finalmente, las corrientes de permeado podrían ser reutilizadas para riego. Por otro lado, la productividad asegurada por la membrana de NF seleccionada fue mayor, en torno a 47.4 L/hm<sup>2</sup> a 9 bar, mientras que 30.9 L/hm<sup>2</sup> pudieron ser producidos por la membrana de OI bajo una presión operativa de 8 bar. Además, un índice de fouling sensiblemente menor fue medido en la membrana de NF (0.0072 en contraste con 0.065), lo que asegura mayor rendimiento en estado estacionario para esta membrana, y mayor vida de servicio. Además, ello también resultó en una menor área de membrana y sobredimensionamiento de la planta requeridas (4 módulos en caso de OI mientras que sólo para NF)
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