Arthrosphira (Spirulina) platensis apresenta substâncias de interesse nas indústrias alimentícia, farmacêutica e cosmética. A produção industrial envolve uma quantidade muito grande de água e sua viabilidade deve contemplar o reuso do meio, visando uma diminuição de custos com nutrientes, bem como da poluição ambiental, tornando-se assim um processo sustentável. O presente trabalho teve como objetivo principal a avaliação do reaproveitamento do meio no cultivo de A. platensis usando tratamentos físico-químicos de floculação e adsorção. Para tanto, tal cianobactéria foi cultivada em fotobiorreator (FBR) tubular em processos de batelada alimentada e contínuo em intensidade luminosa de 120 µmol fótons m-2 s-1, sob controle de pH. Foram desenvolvidas técnicas de tratamento de meio de cultivo proveniente de processo descontínuo alimentado de A. platensis para a remoção de matéria orgânica (MO) e pigmentos (60 - 96 %), permitindo assim seu reuso em novos cultivos. A. platensis foi cultivada nos meios tratados utilizando frascos Erlenmeyer, com avaliação de parâmetros como concentração celular máxima (Xm), conteúdo de clorofila-a (Chl) e conteúdo de proteína na biomassa seca (PTN). No processo simultâneo de floculação e adsorção com carvão ativado em pó (CAP), foram testados dois agentes floculantes, cloreto férrico (F) e sulfato férrico (S) bem como diferentes tempos de contato. No processo simultâneo de floculação com F e adsorção com CAP, as condições ótimas foram: CAP = 24,4 mg L-1 e F = 20,3 mg L-1durante 30,4 min de tempo de contato; com obtenção de: Xm = 4893 ± 33 mg L-1, Chl = 24,3 ± 0,1 mg g-1, PTN = 36,1 ± 0,6 %. As condições ótimas de tratamento simultâneo de floculação com S e adsorção com CAP foram: CAP = 40,0 mg L-1 e S = 32,8 mg L-1 durante 36,1 min de tempo de contato, com obtenção de: Xm = 4863 ± 64 mg L-1, Chl = 24,5 ± 0,6 mg g-1, PTN = 60,1 ± 0,6 %. No processo sequencial de floculação com F seguido de adsorção com carvão ativado granulado (CAG), as condições ótimas foram atingidas com: CAG = 108,4 g e F = 10,0 mg L-1 durante 30,8 min de tempo de residência; obtendo-se: Xm = 3140 ± 77 mg L-1, Chl = 35,4 ± 0,2 mg g-1, PTN = 44,9 ± 0,0 %. Adicionalmente, os meios tratados nessas condições ótimas de cada tratamento, também foram testados em FBR tubulares, atingindo valores de Xm, Chl e PTN maiores do que os obtidos com meio padrão. Além disso, o processo simultâneo de cultivo celular em FBR tubulares e adsorção contínua do meio de cultivo exaurido em coluna de CAG removeu 51 - 79 % de MO e pigmentos. Foi demonstrado que uma proporção de 75 % de meio tratado no meio de alimentação não produz diminuição significativa de produtividade celular (PX) e os resultados foram: concentração celular em estado estacionário (Xs) de 1568 ± 15 mg L-1, PX = 941 mg L-1 d-1, PTN = 42,0 ± 0,6 %, com diminuição de 65 % no custo de meio de cultivo. Por fim, conclui-se que é viável a utilização de processos físico-químicos no tratamento de meio a ser reaproveitado no cultivo de A. platensis, inclusive em FBR tubulares, com apreciável incremento de clorofila-a e proteínas na biomassa obtida em meio tratado. / Arthrospira (Spirulina) platensis have compounds of interest in the food, pharmaceutical and cosmetic industries. Industrial production involves high volumes of water and its viability should contemplate medium reuse, aiming to reduce not only nutrient costs, but also environmental pollution, thus becoming a sustainable process. This work had as main objective the evaluation of A. platensis culture medium reuse through the physicochemical treatments flocculation and adsorption. Thus, this cyanobacterium was cultivated in tubular photobioreactor (PBR) by fed-batch and continuous processes at light intensity 120 µmol photons m-2 s-1 under pH control. Treatment techniques were developed for culture medium from fed-batch process to properly removal of organic matter (OM) and pigments (60 - 96 %), thus allowing its reuse in new cultures. A. platensis was cultivated in treated medium using Erlenmeyer flasks, with the evaluation of parameters such as maximum cell concentration (Xm), chlorophyll content (Chl) and protein content in dry biomass (PTN). For simultaneous flocculation and adsorption with powdered activated carbon (PAC), two flocculants were used: ferric chloride (F) and ferric sulfate (S), as well as different contact times. In the simultaneous process of F flocculation and PAC adsorption, optimum conditions were: PAC = 24.4 mg L-1 and F = 20.3 mg L-1 for 30.4 min contact time; results were: Xm = 4893 ± 33 mg L-1, Chl = 24.3 ± 0.1 mg g-1, PTN = 36.1 ± 0.6 %. Optimal conditions in the simultaneous process of S flocculation and PAC adsorption were: PAC = 40.0 mg L-1 and S = 32.8 mg L-1 for 36.1 min contact time; results were: Xm = 4863 ± 64 mg L-1, Chl = 24.5 ± 0.6 mg g-1, PTN = 60.1 ± 0.6 %. In the sequential process of F flocculation followed by adsorption with granular activated carbon (GAC), optimal conditions were reached at GAC = 108.4 g and F = 10.0 mg L-1 for 30.8 min of residence time, at which Xm = 3140 ± 77 mg L-1, Chl = 35.4 ± 0.2 mg g-1 and PTNPTN = 44.9 ± 0.0 % were obtained. Moreover, medium treated at each optimal condition were also tested in tubular PBRs, reaching values of Xm, Chl and PTN higher than those obtained with standard medium. Furthermore, the simultaneous process of cell cultivation in tubular PBR and continuous adsorption of spent cultivation medium through GAC column removed 51 - 79 % of OM and pigments. It was showed that 75 % of treated medium in the feed medium does not cause significant decrease in cell productivity (PX) and results were: steady-state cell concentration (Xs) = 1568 ± 15 mg L-1, PX = 941 mg L-1 d-1, PTN = 42.0 ± 0.6 %, with 65 % reduction in medium price. At last, it can be inferred that the use of physicochemical processes in medium treatment is feasible for reuse in A. platensis cultivation, including that in tubular PBR, leading to considerable increase in chlorophyll and protein contents of the biomass obtained with treated medium.

Polyacrylamides (PAMs) are a class of polymers formed from acrylamide alone or copolymerized with other monomers. PAMs have been used in drinking water treatment as flocculants or coagulants in the highest volume among all the polymer types. In potable water treatment processes, polyacrylamides are often exposed to oxidants (e.g. chlorine and permanganate) and UV irradiation from sunlight or artificial sources. The purpose of this study is to evaluate the possible degradation of PAMs caused by chemical oxidation and/or UV irradiation. Three types of PAM products (nonionic, cationic and anionic) were studied under free chlorine and permanganate oxidation, UV irradiation, and their combined effects. It has been found that the cationic PAM was the most unstable polymer among the three types of polymer sample studies, however, only partial degradation was observed. Acrylamide residual in the cationic PAM C-3280 was higher than the U.S. guideline value, and exposure to either chlorine or permanganate resulted in decline of acrylamide level to some extent. UV irradiation did not cause reduction of total polymer contents and acrylamide residuals, but did accelerate chemically induced degradation. Exposure to chlorine or permanganate for one hour resulted in about 20-35% loss in flocculation performance for each polymer sample. Short time exposure (5 minutes) did not result in loss of flocculation performance for the nonionic and anionic PAMs. However, for the cationic PAM, even short time exposure to chlorine led to loss of flocculation performance of 25-35 %, which indicated that the cationic PAM was more susceptible to oxidation.

The effect of shear on the evolution of floc properties was investigated to analyse the flocculation mechanisms. Little fundamental attention has been given to the shear influence that often creates compact aggregates, while the floc characteristics might differ in other aggregating conditions. It is thus crucial to understand how flocs evolve to steady state, if their properties are to be 'tailored' to suit subsequent solids-liquid separation processes. In this work, flocculation of monodisperse latex particles of various sizes (60, 380, and 810 nm diameter) via electrolyte addition was carried out in a couette-flow and also in shear fields generated by an axial-flow impeller (Fluid foil A310) and a radial-flow impeller (Rushton R100) in standard mixing tanks. A small-angle light scattering technique was used to acquire information regarding the time variation of floc properties in a non-intrusive manner. The structure was quantified by a measure of fractal dimension, signifying the degree of floc compactness. Estimates of the average floc mass were also obtained from the aggregate scattering patterns. By monitoring the changes in floc structure and mass, corresponding to the size evolution; mechanisms of floc formation, fragmentation, and restructuring were identified. Aggregates of 60 and 380 nm particles were observed to grew larger initially, before decreasing to their equilibrium sizes at moderate shear rates (32 - 100 s-1) in a homogeneous shear environment. Floc restructuring at large length scales occurred extensively, and was responsible for the drop in size, particularly at the early stage of the process. Aggregates of 810 nm particles did not, however, display this behaviour. Flocs of larger primary particles were presumably susceptible to breakage rather than deformation, as they were weaker under comparable conditions. Denser aggregates were found when restructuring transpired, while comparatively tenuous flocs were observed when formation and breakage kinetics were the governing mechanisms. The disparity in floc behaviour at higher shear rates (246 s-1 - 330 s-1) was less apparent. The intense hydrodynamic stresses in those instances inevitably caused fragmentation, regardless of the intrinsic particle properties; hence the observed floc compaction was the product of break-up and re-aggregation. A population balance model, incorporating variation in floc structure, displayed comparable trends in size evolution; verifying that restructuring indeed took an important role under certain flocculation conditions. Similar phenomena were likewise observed with the flocculation in stirred tanks. The results reinforced findings in literature; that while circulation time controlled the process kinetics; the floc size was determined by the turbulent stresses. In addition, the maximum shear levels also influenced the floc structures, with denser aggregates produced in a shear field generated using the radial-flow impeller at equivalent energy dissipation per-unit mass. A correlation between non-dimensional floc factor that embodied the aggregate size and structure, and aggregation factor comprising the significant parameters from flocculation conditions, was proposed. The proposed relationship takes into account aspects such as the aggregate structure, interparticle forces, and particle concentration that are often overlooked in existing relationships, which usually only relate the maximum floc size to the applied energy dissipation rate. It thus provides an improved manner of presenting general flocculation data, as well as a means to predict floc properties produced under a specific aggregation condition. Future studies with increasingly complex systems that resemble real conditions are recommended in order to establish a practical understanding of the flocculation mechanisms, for the purpose of optimising the aggregate properties.

The effectiveness of partial ozonation of return activated sludge for enhancing denitrification and waste sludge minimization were examined. A pair of nitrifying sequencing batch reactors was operated in either aerobic or alternating anoxic/aerobic conditions, with one control and one ozonated reactor in each set. The amount of solids decreased with the ozone dose. Biomass in the anoxic/aerobic reactor was easier to destroy than in the aerobic one, generating approximately twice as much soluble chemical oxygen demand (COD) by cell lysis. Increased COD favoured production of extracellular polymers in ozonated reactors, enhancing flocculation and improving settling. Floc stability was also strengthened in prolonged operation in alternating treatment, resulting in declined solids destruction. Dewaterability was better in alternating reactors than in aerobic ones indicating that incorporation of an anoxic zone for biological nutrient removal leads to improvement in sludge dewatering. The negative impact of ozonation on dewaterability was minimal in terms of the long-term operation. Ozone successively destroyed indicator estrogenic compounds, contributing to total estrogen removal from wastewater. Denitrification rate improved up to 60% due to additional carbon released by ozonation. Nitrification rates deteriorated much more in the aerobic than in the alternating reactor, possibly as a result of competition created by growth of heterotrophs receiving the additional COD. Overall, ozonation provided the expected benefits and had less negative impacts on processes in the alternating treatment, although after prolonged operation, benefits could become less significant. The alternating anoxic/aerobic reactor achieved twice the nitrification rates of its aerobic counterpart. Higher removal rates of estrogens were associated with higher nitrification rates, supporting the contention that the nitrifying biomass was responsible for their removal. The alternating treatment offered the better estrogen biodegradation. Microbial populations in both reactors were examined with fluorescent in situ hybridization. Dominance of rapid nitrifiers like Nitrosomonas and Nitrobacter (79.5%) in the alternating reactor, compared to a dominance of slower nitrifiers like Nitrosospira and Nitrospira (78.2%) in the aerobic reactor were found. The findings are important to design engineers, as reactors are typically designed based on nitrifiers’ growth rate determined in strictly aerobic conditions. / October 2008

In order to avoid harmful substances ending up at the municipal sewage treatment plants, it is important to purify the wastewater at the source. One such source is the wheel washers available in many tire garages which are used to wash the wheels on our vehicles when we change between summer and winter tires. It is important to wash the wheels before storage, to extend the tires lifetime. The purpose of this study is to find a green innovative solution for reduction of emissions of heavy metals at the source, so that the sludge from the sewage treatment plants can be used as fertilizer. The target is to find a wheel wash method which leads to compliance with the guidelines for car washers, and that also provides a better washing result than with the existing method. Chemical analyzes of water samples have been performed and the cleanliness of the wheels has been checked visually. As there are no specific emission requirements for wheel washes, the results have mainly been compared with current guidelines for vehicle washes. A new washing and flocculation method have been developed during the study. The proposed new method is suitable as pretreatment of the water before discharging it, as it reduces metal emissions and provides better washing results compared to the old method. Significantly larger number of wheels may be washed in one session, which leads to a reduction of water- and energy consumption since the machine can be emptied and cleaned less often. For many years there has been an environmental adaption to eco-friendly car washers, so the opportunities should be good for wheel washers to win goodwill and market advantages by being profiled with an environmentally adapted washing method. / För att undvika att miljöskadliga ämnen hamnar i de kommunala reningsverken är det viktigt att rena avloppsvattnet vid källan. En sådan källa är de hjultvättmaskiner som finns på många verkstäder och som används för att tvätta hjulen på våra fordon i samband med skifte mellan sommar- och vinterdäck. Det är viktigt att tvätta hjulen före förvaring, för att förlänga däckens livslängd. Syftet med denna undersökning är att hitta en grön innovativ lösning för att främja uppströmsarbetet, dvs att rena utsläppen av tungmetaller vid källan, så att slammet från våra reningsverk kan användas som gödningsmedel. Målet är att finna en metod för hjultvätt som medför att riktlinjerna för fordonstvättar uppfylls, och som samtidigt ger ett bättre tvättresultat än befintlig metod. Kemiska analyser av vattenprover har utförts och renheten har kontrollerats visuellt. Eftersom det saknas specifika utsläppskrav för hjultvättar, har resultaten i första hand jämförts med gällande riktlinjer för fordonstvättar. En ny tvätt- och flockningsmetod har utvecklats under studiens gång. Den föreslagna nya metoden är lämplig som förbehandling av vattnet innan utsläpp, eftersom den sänker metallutsläppen samt ger ett bättre tvättresultat jämfört med den gamla metoden. Betydligt fler hjul kan tvättas per tvättomgång vilket innebär en minskning av vatten- och energiförbrukningen eftersom maskinen behöver tömmas och rengöras mer sällan. Under många år har det skett en miljöanpassning av fordonstvättar, så möjligheterna borde vara goda för att även hjultvättar ska kunna vinna goodwill och marknadsmässiga fördelar genom att profilera sig med en miljöanpassad tvättmetod.

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Formation plays an important role in the end-use properties of paper products, but before formation can be optimized to achieve superior properties, an understanding about the causes of formation must be developed. Formation is caused by variations in the basis weight of paper that are results of fiber floc formation before and during the forming of the sheet. This project is a first step in a larger research program aimed at studying formation. By observing the effects that mechanical energy dissipation (in the form of turbulence) and retention chemical dosage have on floc formation, we may develop a better understanding of how to control formation. In this study, a rectangular cross-section flow channel was constructed to aid in the acquisition of digital images of a flowing fiber suspension. The furnish consisted of a 55:45 spruce:pine bleached market pulp mix from a Western Canadian mill. Turbulence was varied by changing the flow rate; Reynolds numbers achieved range from 20,000 to 40,000. The retention aid used was a cationic polyacrylamide with a medium charge density. Dosage of the retention aid was varied from 0 to 2 pounds per ton OD fiber. Digital images of the flowing fiber suspension were acquired with a professional digital SLR camera with a forensics-quality lens. Three separate image analysis techniques were used to measure the flocculation state of the fiber suspension: morphological image operations, formation number analysis, and fast Fourier transform analysis. Morphological image analysis was capable of measuring floc size increases seen in the acquired floc images. It was shown how floc diameter could increase simultaneously with decreasing total floc area and total floc number. A regression model relating retention aid dosage and energy dissipation was constructed in an effort to predict flocculation. The regression model was used to predict F2 (formation number squared) results from the study. The interaction effect RE was shown to have a differing effect across the retention aid dosage levels. As a result, this model and technique may prove to be a beneficial tool in optimizing retention aid applications.

This study presents quantitative results on the effect on individual fiber length during fiber flocculation. Flocculation was induced by a cationic polyacrylamide (cPAM). A high speed camera recorded 25 second video clips. The videos were image-analyzed and the fiber length and the amount of fiber in each sample were measured. Prior to the flocculation process, fibers were fractionated into short and long fibers. Trials were conducted using the unfractionated fiber, short fiber, and long fiber. The short and long fibers were mixed in several trials to study the effect of fiber length. The concentration of cPAM was varied as well as the motor speed of the impeller (RPM). It was found that the average fiber length decreased more rapidly with increasing motor speed. Increasing the concentration of cPAM also led to a greater decrease in average fiber length. A key finding was that a plateau was reached where further increasing the amount of cPAM had no effect. Hence, fibers below a critical length resisted flocculation even if the chemical dose or shear was increased. This critical length was related to the initial length of the fiber.

As high grade iron ore deposits are rapidly depleted, the minerals industry is increasingly obliged to enrich their ores and process lower grade iron ores. Production of large quantities of fine ores as tailings or by-products in mining operations and mineral liberation at fine particle sizes have led to the development of concentration methods employed to fine ores. Selective flocculation is one of the beneficial methods which can be used in recovering of very fine particles It is obvious that process water chemistry has a significant influence on the flocculation efficiency, and the water chemistry is deeply affected by carbon dioxide dissolution. Carbonate content of natural waters regulated by CO2, carbonicacid and solid carbonatesis known as &lsquo / carbonate alkalinity&rsquo / whichmay be an important factor in flocculation especially at alkaline pH. Selective flocculation of iron ores is usually run at around pH 11 where carbonate alkalinity could be rather high. There have been no reports in literature regarding the effect of carbonate alkalinity on the flocculation behavior of iron oxides, mainly hematite. In this study, the flocculation behavior of iron ores with starch under different alkalinities has been investigated. The extent of flocculation has been assessed by settling rate and suspended solid content measurements at different starch doses and pH values. Zeta potential measurements and starch adsorption studies were carried out to explain these effects by carbonate alkalinity. According to the results, flocculation is enhanced by addition of low amount of carbonate alkalinity, less than 2.4 mEq/L. However, adding the higher amount of alkalinity adversely affected the flocculation of hematite. Similar behavior was also observed during the starch adsorption tests, larger amount of starch wasadsorbed by hematite in low alkalinity compared to high alkalinity. Zeta potential measurements indicate that, by increasing the carbonate alkalinity of suspension, zeta potential values of solids will become more negativeleading to an increase in the stability of suspension and then adversely affecting flocculation. Therefore, as carbonate alkalinity has a significant effect on the flocculation of hematite, it should be seriously taken into account to optimize the selective flocculation of hematite ores.