Effect of physico-chemical conditions and operating parameters on flux and retention of different components in ultrafiltration and nanofiltration fractionation of sweet whey

Tässä väitöstutkimuksessa tutkittiin fysikaaliskemiallisten olosuhteiden ja toimintaparametrien vaikutusta juustoheran fraktiointiin. Kirjallisuusosassa on käsitelty heran ympäristövaikutusta, heran hyödyntämistä ja heran käsittelyä kalvotekniikalla. Kokeellinen osa on jaettu kahteen osaan, joista ensimmäinen käsittelee ultrasuodatusta ja toinen nanosuodatusta juustoheran fraktioinnissa. Ultrasuodatuskalvon valinta tehtiin perustuen kalvon cut-off lukuun, joka oli määritetty polyetyleeniglykoliliuoksilla olosuhteissa, joissa konsentraatiopolariosaatioei häiritse mittausta. Kriittisen vuon konseptia käytettiin sopivan proteiinikonsentraation löytämiseksi ultrasuodatuskokeisiin, koska heraproteiinit ovat tunnetusti kalvoa likaavia aineita. Ultrasuodatuskokeissa tutkittiin heran eri komponenttien suodattumista kalvon läpi ja siihen vaikuttavia ominaisuuksia. Herapermeaattien peptidifraktiot analysoitiin kokoekskluusiokromatografialla ja MALDI-TOF massaspektrometrillä. Kokeissa käytettävien nanosuodatuskalvojen keskimääräinen huokoskoko analysoitiin neutraaleilla liukoisilla aineilla ja zeta-potentiaalit virtauspotentiaalimittauksilla. Aminohappoja käytettiin malliaineina tutkittaessa huokoskoon ja varauksen merkitystä erotuksessa. Aminohappojen retentioon vaikuttivat pH ja liuoksen ionivahvuus sekä molekyylien väliset vuorovaikutukset. Heran ultrasuodatuksessa tuotettu permeaatti, joka sisälsi pieniä peptidejä, laktoosia ja suoloja, nanosuodatettiin happamassa ja emäksisessä pH:ssa. Emäksisissä oloissa tehdyssä nanosuodatuksessa foulaantumista tapahtui vähemmän ja permeaattivuo oli parempi. Emäksisissä oloissa myös selektiivisyys laktoosin erotuksessa peptideistä oli parempi verrattuna selektiivisyyteen happamissa oloissa.

The Influence of Process Conditions on the Deresination Efficiency in Mechanical Pulp Washing

The aim of this thesis was to produce information for the estimation of the flow balance of wood resin in mechanical pulping and to demonstrate the possibilities for improving the efficiency of deresination in practice. It was observed that chemical changes in wood resin take place only during peroxide bleaching, a significant amount of water dispersed wood resin is retained in the pulp mat during dewatering and the amount of wood resin in the solid phase of the process filtrates is very small. On the basis of this information there exist three parameters related to behaviour of wood resin that determine the flow balance in the process: 1. The liberation of wood resin to the pulp water phase 2. Theretention of water dispersed wood resin in dewatering 3. The proportion of wood resin degraded in the peroxide bleaching The effect of different factors on these parameters was evaluated with the help of laboratory studies and a literature survey. Also, information related to the values of these parameters in existing processes was obtained in mill measurements. With the help of this information, it was possible to evaluate the deresination efficiency and the effect of different factors on this efficiency in a pulping plant that produced low-freeness mechanical pulp. This evaluation showed that the wood resin content of mechanical pulp can be significantly decreased if there exists, in the process, a peroxide bleaching and subsequent washing stage. In the case of an optimal process configuration, as high as a 85 percent deresination efficiency seems to be possible with a water usage level of 8 m3/o.d.t.

Development of fibre recovery process

The fiber recovery process is an essential part of the modern paper mill. It creates the basisfor mill's internal recirculation of the most important raw materials ¿ water and fiber. It is normally also a start point for further treatment of wastewater and if it works efficiently, it offers excellent basis to minimize effluents. This dissertation offers two different approaches to the subject. Firstly a novel save-all disc filter feeding system is developed and presented. This so-called precoat method is tested both in the laboratory and full-scale conditions. In laboratory scale it beats the traditional one clearly, when low freeness pulps are used as a sweetener stock. The full-scale application needs still some development work before it can be implemented to the paper mills. Secondly, the operationenvironment of save-all disc filter is studied mostly in laboratory conditions.The focus of this study is in cases, where low-freeness pulps are used as a sweetener stock of save-all filter. The effects of CSF-value, pressure drop, suspension consistency and retention chemicals to the quantity and quality of the filtrate was studied. Also the filtration resistance of the low freeness pulps was one studied.

Fouling, prevention of fouling, and clearing in filtration

In this thesis fouling of conventional filter fabrics and membranes was studied. In the beginning of the thesis fouling and how it can be measured and predicted is reviewed. Information on different methods on how fouling canbe decreased or cleaned away is also given. The experimental part is divided into two sections; fabric filtration and membrane filtration. Fouling of the filter fabrics was studied with silica or cupper slurries and fouling of the membranes was studied with pulp and paper mill waters. The fouled filter materials were characterised according to many different methods. The most useful way to observe fouling is to measure the changes in the permeate flux. Fouling can also be seen visually e.g. with scanning electron microscopy. Consequently, also the reason for the fouling in question might be found. Different filtration characteristics affect fouling e.g. as the filtration pressure was increased it did not have much influence on the permeate flux, but the pressure caused the membrane to get fouled faster. Also, an increase of shear rate on the membrane surface decreased fouling. Different pretreatment methods for the effluent were tested in membrane filtration to decrease fouling. The tested methods; biological treatment, ozonation, enzymatic treatment and flocculation, did not have a clear influence on the fouling of the membrane, but e.g. a biological treatment combined with ultrafiltration made the tested groundwood mill circulation water purer than ultrafiltration alone.

Gas exchange of the umbu tree under semi-arid conditions

A study was carried out at Embrapa Semi-Árido, Petrolina-PE, Brazil, aiming to understand the gas exchange process of the umbu tree (Spondias tuberosa Arr. Cam.) in the dry and rainy seasons. Stomatal conductance, transpiration, photosynthesis and internal CO2 concentration were obtained with a portable infrared gas analyzer (IRGA). During the dry season the umbu tree showed a much lower stomatal conductance early in the morning, as soon as the vapor pressure deficit increased, apparently affecting CO2 assimilation more than transpiration. The highest values were detected around 6:00 am but decreased to the lowest points between 10:00 am and 2:00 pm. During the rainy season, however, stomatal conductance, transpiration and photosynthesis were significantly higher, reaching the highest values between 8:00 and 10:00 am and the lowest around 2:00 pm. It was also observed at 4:00 pm, mainly during the rainy season, an increase on these variables indicating that the umbu tree exhibits a two-picked daily course of gas exchange.

Variation of grain nitrogen content in relation with grain yield in old and modern Spanish wheats grown under a wide range of agronomic conditions in a Mediterranean region

Wheat yield and grain nitrogen concentration (GNC; mg N/g grain) are frequently negatively correlated. In most growing conditions, this is mainly due to a feedback process between GNC and the number of grains/m2. In Mediterranean conditions, breeders may have produced cultivars with conservative grain set. The present study aimed at clarifying the main physiological determinants of grain nitrogen accumulation (GNA) in Mediterranean wheat and to analyse how breeding has affected them. Five field experiments were carried out in north-eastern Spain in the 2005/06 and 2006/ 07 growing seasons with three cultivars released at different times and an advanced line. Depending on the experiment, source-sink ratios during grain filling were altered by reducing grain number/m2 either through pre-anthesis shading (unshaded control or 0.75 shading only between jointing and anthesis) or by directly trimming the spikes after anthesis and before the onset of the effective grain filling period (un-trimmed control or spikes halved 7–10 days after anthesis). Grain nitrogen content (GN content ; mg N/grain) decreased with the year of release of the genotypes. As the number of grains/m2 was also increased by breeding there was a clear dilution effect on the amount of nitrogen allocated to each grain. However, the increase in GN content in old genotypes did not compensate for the loss in grain nitrogen yield (GNY) due to the lower number of grains/m2. GN content of all genotypes increased (increases ranged from 0.13 to 0.40 mg N/grain, depending on experiment and genotype) in response to the post-anthesis spike trimming or pre-anthesis shading. The degree of source-limitation for GNA increased with the year of release of the genotypes (and thus with increases in grain number/m2) from 0.22 (mean of the four manipulative experiments) in the oldest cultivar to 0.51 (mean of the four manipulative experiments) in the most modern line. It was found that final GN content depended strongly on the source-sink ratio established at anthesis between the number of grains set and the amount of nitrogen absorbed at this stage. Thus, Mediterranean wheat breeding that improved yield through increases in grain number/m2 reduced the GN content by diluting a rather limited source of nitrogen into more grains. This dilution effect produced by breeding was further confirmed by the reversal effect produced by grain number/m2 reductions due to either pre-anthesis shading or post-anthesis spike trimming.

Grain yield, carbon isotope discrimination and mineral content in mature kernels of barley under irrigated and rainfed conditions

The relationship between yield, carbon isotope discrimination and ash content in mature kernels was examined for a set of 13 barley (Hordeum vulgare) cultivars. Plants were grown under rainfed and well-irrigated conditions in a Mediterranean area. Water deficit caused a decrease in both grain yield and carbon isotope discrimination (Δ). The yield was positively related to Δ and negatively related to ash content, across genotypes within each treatment. However, whereas the correlation between yield and Δ was higher for the set of genotypes under well-irrigated (r=0.70, P<0.01) than under rainfed (r=0.42) conditions, the opposite occurred when yield and ash content were related, ie r=-0.38 under well-irrigated and r=-0.73, (P<0.01) under rainfed conditions. Carbon isotope discrimination and ash content together account for almost 60% of the variation in yield, in both conditions. There was no significant relationship (r=-0.15) between carbon isotope discrimination and ash content in well-irrigated plants, whereas in rainfed plants, this relationship, although significant (r=-0.54, P< 0.05), was weakly negative. The concentration of several mineral elements was measured in the same kernels. The mineral that correlated best with ash content, yield and A, was K. For yield and Δ, although the relationship with K followed the same pattern as the relationhip with ash content, the correlation coefficients were lower. Thus, mineral accumulation in mature kernels seems to be independent of transpiration efficiency. In fact, filling of grains takes place through the phloem pathway. The ash content in kernels is proposed as a complementary criterion, in addition to kernel Δ, to assess genotype differences in barley grain yield under rainfed conditions.

Effect of water velocity on the uptake of polychlorinatedd biphenyls (PCBs) by silicone rubber (SR) and low-density polyethylene (LDPE) passive samplers: an assessment of the efficiency of performance reference compounds (PRCs) in river-like flow conditions

One aim of this study is to determine the impact of water velocity on the uptake of indicator polychlorinated biphenyls (iPCBs) by silicone rubber (SR) and low-density polyethylene (LDPE) passive samplers. A second aim is to assess the efficiency of performance reference compounds (PRCs) to correct for the impact of water velocity. SR and LDPE samplers were spiked with 11 or 12 PRCs and exposed for 6 weeks to four different velocities (in the range of 1.6 to 37.7 cm s−1) in river-like flow conditions using a channel system supplied with river water. A relationship between velocity and the uptakewas found for each iPCB and enables to determine expected changes in the uptake due to velocity variations. For both samplers, velocity increases from 2 to 10 cm s−1, 30 cm s−1 (interpolated data) and 100 cm s−1 (extrapolated data) lead to increases of the uptake which do not exceed a factor of 2, 3 and 4.5, respectively. Results also showed that the influence of velocity decreased with increasing the octanol-water coefficient partition (log Kow) of iPCBs when SR is used whereas the opposite effect was observed for LDPE. Time-weighted average (TWA) concentrations of iPCBs in water were calculated from iPCB uptake and PRC release. These calculations were performed using either a single PRC or all the PRCs. The efficiency of PRCs to correct the impact of velocity was assessed by comparing the TWA concentrations obtained at the four tested velocities. For SR, a good agreement was found among the four TWA concentrations with both methods (average RSD b 10%). Also for LDPE, PRCs offered a good correction of the impact of water velocity (average RSD of about 10 to 20%). These results contribute to the process of acceptance of passive sampling in routine regulatory monitoring programs.

Nitrogen replacement value of alfalfa to corn and wheat under irrigated Mediterranean conditions

In crop rotations that include alfalfa (Medicago sativa L.), agronomic and environmental concerns mean that it is important to determine the N fertilizer contribution of this legume for subsequent crops in order to help to increase the sustainability of cropping systems. To determine the N fertilizer replacement value (FRV) of a 2-yr alfalfa crop on subsequent crops of corn (Zea mays L.) followed by wheat (Triticum aestivum L.) under irrigated Mediterranean conditions, two 4-yr rotations (alfalfa-corn-wheat and corn-corn-corn-wheat) were conducted from 2001 to 2004 in a Typic Xerofluvent soil. Corn yields were compared after two years of alfalfa and a third year of corn under monoculture and wheat yields were also compared after both rotations. Corn production after alfalfa outyielded monoculture corn at all four rates of N fertilizer application analyzed (0, 100, 200 and 300 kg N/ha). The FRV of 2-yr alfalfa for corn was about 160 kg N/ha. Wheat grown after the alfalfa-corn rotation outyielded that grown after corn under monoculture at both the rates of N studied (0 and 100 kg N/ha). The FRV of alfalfa for wheat following alfalfa-corn was about 76 kg N/ha. Soil NO3 -N content after alfalfa was greater than with the corn monoculture at all rates of N fertilizer application and this higher value persisted during the second crop after alfalfa. This was probably one of the reasons for the better yields associated with the alfalfa rotation. These results make a valuable contribution to irrigated agriculture under mediterranean conditions, show reasons for interest in rotating alfalfa with corn, and explain how it is possible to make savings when applying N fertilizer.