Optimization of Operation Parameters in Ultrafiltration by Experiment Design, Mathematical Modelling and Fouling Characterization of the Membranes Used to Remove Dissolved and Colloidal Substances from a Treated Paper Mill Effluent

[ES] En la presente Tesis Doctoral se investigó la aplicación del proceso de ultrafiltración (UF) y el fenómeno de ensuciamiento de las membranas en la eliminación de sustancias disueltas y coloidales (DCS) de efluentes tratados de la industria papelera (PMTE) para su reutilización en los diferentes procesos de fabricación de papel y cartón reciclado. El objetivo general de esta investigación se dividió en tres partes principales: i) describe cómo encontrar las condiciones óptimas de operación de cuatro parámetros de proceso: presión transmembrana (TMP), velocidad de flujo cruzado (CFV), temperatura y corte de peso molecular (MWCO) para maximizar el flujo promedio de permeado (Jp) y rechazo de la demanda química de oxígeno (COD) y minimizar el descenso del flujo de permeado acumulado (SFD) utilizando el método de Taguchi (Design Robusto) y utility concept aplicado a un proceso de UF a flujo cruzado, para remover DCS de efluentes tratados de la industria papelera, ii) el descenso del flujo de permeado y los mecanismos de ensuciamiento de las membranas de UF ensuciadas con PMTE se examinaron mediante modelos matemáticos semi-empíricos. Los resultados para los diferentes ensayos de UF se expresaron en términos de variación del Jp en función del tiempo para verificar la precisión del ajuste (mayor valor de R2 y menor valor de desviación estándar) de los distintos modelos de Hermia adaptados a flujo tangencial y del modelo de formación de torta en filtración a presión constante ajustados a los datos experimentales, y iii) describe métodos de identificación, caracterización y posibles orígenes de las sustancias contaminantes (foulants) en las membranas de UF. Técnicas como el análisis físico-química, FESEM, SEM-EDS, ATR-FTIR y 3DEEM se llevaron a cabo para comprender qué fracción de los contaminantes son responsables por la formación de incrustaciones en las membranas. Los resultados obtenidos durante la etapa de optimización de parámetros del procesos demostraron que TMP y MWCO tienen la mayor contribución en el Jp y SFD. En el caso de la tasa de rechazo de COD, los resultados mostraron que MWCO tiene la mayor contribución seguida de CFV. Por consiguiente, las condiciones óptimas se encontraron para el segundo nivel de TMP (2.0 bar), el tercer nivel del CFV (1.041 m/s), el segundo nivel de la temperatura (15°C) y el tercer nivel de MWCO (100 kDa). Bajo estas condiciones óptimas de operación Jp, rechazo de COD y SFD alcanzaron respuestas de 81.15 L/m2.h, 43.90% y 6.01 (alrededor de 28.96 % para (FD), respectivamente, valores dentro del rango previsto del intervalo de confianza del 95%. Además, los modelos de Hermia adaptados a UF en flujo tangencial fueron capaces de predecir con gran precisión el descenso del Jp y los mecanismos de ensuciamiento en función del tiempo para todas las membranas seleccionadas (10, 30 y 100 kDa) y bajo diferentes condiciones ensayadas de UF. Por lo tanto, los modelos que presentan un mayor grado de ajuste son el bloqueo completo de poros (coeficiente de determinación R2 >0.97) y bloqueo intermedio (R2 >0.96), seguido por el modelo de formación de torta (R2 >0.94), lo que indica que estés son los principales mecanismos de ensuciamiento de las membranas. Análisis de 3DEEM revelaron que la mayoría de la materia orgánica fluorescentes en las membranas sucias eran proteínas coloidales (componentes similares a proteínas I + II) y proteínas macromoleculares (componentes similares a SMP). Además, polisacáridos (especie celulósica) y sustancias como ácidos grasos y resinosos fueron identificadas en las membranas contaminadas mediante análisis ATR-FTIR. Por fin, análisis SEM-EDS para las membranas ensuciadas con PMTE se detectó concentración de contaminantes inorgánicos (iones metálicos multivalentes) especialmente el Ca2+ que podría acelerar la formación torta en la superficie de la membrana.[CA] En la present Tesi Doctoral es va investigar l'aplicació del procés d'ultrafiltració (UF) i el fenomen d'embrutiment de les membranes en l'eliminació de substàncies dissoltes i col·loïdals (DCS) d'efluents tractats de la indústria paperera (PMTE) per al seu reutilització en els diferents processos de fabricació de paper i cartó reciclatge. L'objectiu general d'aquesta investigació es va dividir en tres parts principals: i) descriu com trobar les condicions òptimes d'operació de quatre paràmetres de procés: pressió transmembrana (TMP), velocitat de flux creuat (CFV), temperatura i tall de pes molecular (MWCO) per a maximitzar el flux mitjà de permeat (Jp) i rebuig de la demanda química d'oxigen (COD) i minimitzar el descens del flux de permeado acumulat (SFD) utilitzant el mètode de Taguchi (Design Robust) i utility concept aplicat a un procés de UF a flux creuat en escala pilot, per a remoure DCS d'efluents tractats de la indústria paperera (PMTE), ii) el descens del flux de permeat i els mecanismes de embrutiment (fouling) de les membranes de UF embrutades amb PMTE es van examinar mitjançant models matemàtics semi-empírics. Els resultats per als diferents assajos de UF es van expressar en termes de variació del flux de permeat (Jp) en funció del temps per a verificar la precisió de l'ajust (major valor de R2 i menor valor de desviació estàndard) dels diferents models de Hermia adaptats a flux tangencial i del model de formació de coca en filtració a pressió constant ajustats a les dades experimentals, i iii) descriu mètodes d'identificació, caracterització i possibles orígens de les substàncies contaminants (foulants) en les membranes de UF. Tècniques com l'anàlisi física-química, FESEM, SEM-EDS, ATR-FTIR i 3DEEM es van dur a terme per a comprendre quina fracció dels contaminants són responsables per la formació d'incrustacions sobre la superfície i adsorció dins dels porus de les membranes. Els resultats obtinguts durant l'etapa d'optimització de paràmetres del processos van demostrar que TMP i MWCO tenen la major contribució en el Jp i SFD. En el cas de la taxa de rebuig de COD, els resultats van mostrar que MWCO té la major contribució seguida de CFV. Per consegüent, les condicions òptimes es van trobar per al segon nivell de TMP (2.0 bar), el tercer nivell del CFV (1.041 m/s), el segon nivell de la temperatura (15°C) i el tercer nivell de MWCO (100 kDa). Sota aquestes condicions òptimes d'operació Jp, rebuig de COD i SFD van aconseguir respostes de 81.15 L/m².h, 43.90% i 6.01 (al voltant de 28.96% per a (FD)), respectivament, valors dins del rang previst de l'interval de confiança del 95%. A més, els models de Hermia adaptats a UF en flux tangencial van ser capaços de predir amb gran precisió el descens del Jp i els mecanismes de embrutiment en funció del temps per a totes les membranes seleccionades (10, 30 i 100 kDa) i baix diferents condicions assajades de UF. Per tant, els models que presenten un major grau d'ajust són el bloqueig complet de porus (coeficient de determinació R2 >0.97) i bloqueig intermedi (R2 >0.96), seguit pel model de formació de coca (R2 >0.94), la qual cosa indica que estigues són els principals mecanismes de embrutiment de les membranes. Anàlisi de 3DEEM van revelar que la majoria de la matèria orgànica fluorescents en les membranes brutes eren proteïnes col·loidals (components similars a proteïnes I + II) i proteïnes macromoleculars (components similars a SMP). A més, polisacàrids (espècie cel·lulòsica) i substàncies com a àcids grassos i resinosos van ser identificades en les membranes contaminades mitjançant anàlisis ATR-FTIR, tals substàncies exerceixen un paper important en el embrutiment de les membranes. Per fi, anàlisi SEM-EDS per a les membranes embrutades amb PMTE es va detectar concentració de contaminants inorgànics (ions metàl·lics multivalents) especialment el Ca2+ que podria accelerar la formació coca en la àrea de la membrana.[EN] In this PhD Thesis, the application of ultrafiltration process (UF) and membrane fouling phenomenon used to remove dissolved and colloidal substances (DCS) from paper mill treated effluent (PMTE) for reuse in different recycled paper and cardboard manufacturing processes was investigated. The overall goal of this research has been divided into three main parts: i) describes how to find optimal operating conditions of four controlling parameters, such as transmembrane pressure (TMP), cross-flow velocity (CFV), temperature and molecular weight cut-off (MWCO) for maximizing the average permeate flux (Jp) and chemical oxygen demand (COD) rejection, and minimizing the cumulative flux decline (SFD) using Taguchi method and utility concept for a cross-flow UF in pilot scale, used to remove DCS from a paper mill treated effluent (PMTE), ii) flux decline and fouling mechanisms of UF membranes fouled with PMTE were examined by theoretical modelling. The results from UF tests were expressed in terms of permeate flux (Jp) as a function of time to check modified Hermia's models adapted to crossflow filtration and cake formation in constant-pressure filtration, and iii) describes the Identification, characterization and possible origins of UF membrane foulants. Techniques such as chemical analysis, FESEM, SEM-EDS, ATR-FTIR and 3DEEM analysis were applied to understand which fraction of the foulants caused the fouling. This research found that the TMP and MWCO have the greatest contribution to the average permeate flux and SFD. In the case of the COD rejection rate, the results showed that MWCO has the highest contribution followed by CFV. The optimum conditions were found to be the second level of TMP (2.0 bar), the third level of the CFV (1.041 m/s), the second level of the temperature (15°C), and the third level of MWCO (100 kDa). Under these optimum conditions Jp, COD rejection and SFD resistance of 81.15 L/m2/h, 43.90% and 6.01 (around 28.96 % of (FD), respectively, were obtained and they were within of the predicted range at the 95% confidence interval. Furthermore, the results showed that the predictions of the modified Hermia's models adapted to cross-flow UF had good agreements with experimental data, under different conditions tested for PMTE. Therefore, it can be concluded that for all cases the best fit (higher accuracy) to the experimental data corresponds to the complete (coefficient of determination R2 >0.97) and intermediate (R2 >0.96) blocking, followed by the cake layer formation (R2 >0.94). Moreover, measurements of particle size distribution and zeta potential near the isoelectric point, showed a substantial reduction in colloidal compounds. The 3DEEM analysis revealed that the majority of the organic foulants with fluorescence characteristics on the fouled membranes were colloidal proteins (protein-like substances I+II) and macromolecular proteins (SMP-like substances). Further, polysaccharide (cellulosic specie), fatty and resin acid substances were identified on the fouled membrane by the ATR-FTIR analysis and they play an important role in membrane fouling. In addition, the membrane SEM-EDS analysis showed accumulate and adsorbed onto the membrane surfaces of inorganic foulants, such as multivalent metal ions and especially Ca2+ (acts as a binding agent) that could accelerate cake layer formation on the membrane.Santos Sousa, MR. (2020). Optimization of Operation Parameters in Ultrafiltration by Experiment Design, Mathematical Modelling and Fouling Characterization of the Membranes Used to Remove Dissolved and Colloidal Substances from a Treated Paper Mill Effluent [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/155975TESI

Development of advanced oxidation processes for the Finnish pulp and paper industry water treatment

Advanced oxidation processes (AOP) have been developed as a pinnacle of chemical water treatment to face the more tightening environmental limits during the last three decades. Whenever either pure coagulation & flocculation or/and biological technologies cannot reach the required environmental limits, then AOP technologies can be used. This thesis presents four AOP methods to treat different pulp and paper water types. The first study object is to enhance the conventional treatment CODcr removal by placing the AOPs as a tertiary treatment step after the existing activated sludge process. The second study focuses on reducing chemical and investment costs associated with the first study by placing the AOP before the activated sludge by modifying the difficult biodegradable matter to more readily biodegradable. The more biodegradable wastewater can then be removed more efficiently in the following activated sludge stage. The third study uses AOP for more environmentally friendly and economical biocides used on paper machines for biological growth control, simultaneously reducing the recalcitrant compounds found in wastewater. The fourth study aims at removing manganese from the incoming raw water using a new non-toxic, environmentally friendly oxidation method. This new environmentally friendly oxidation method can replace used recalcitrant compounds used in the pulp and paper process. The presented AOP shows its ability to adapt and reach high removal efficiencies for CODCr and Ptot removal in cases known to be challenging to biological treatment only. Suggestions for further AOP development include maximising the utilisation of the existing equipment and chemistries already at the site to lower the initial operational and capital expenses needed to obtain the suggested AOP. Simultaneously, simplifying the presented new AOP toward a more straightforward process with less process and required chemicals is preferred.Avancerade Oxidation Processer (AOP) har utvecklats för den finska massa- och pappersindustrin under de senaste tre senaste decennierna för situationer då processer baserade på sedimentation, kemisk fällning och biologisk rening inte uppnår satta gränsvärden. Finland fick sin första miljölagstiftning 1961. I lagstiftningen var fokus på reglering av avfallsvattenvolymen, på vattnets pH-värde samt på mängden suspenderade ämnen. I slutet av 1970-talet uppstod en diskussion kring behovet av nya begränsningar för att minska utsläppen av biologiskt nedbrytbara ämnen och fosfor. Dessa utsläpp orsakade kraftigt tillväxt av alger och annan mikroskopisk biomassa som i sin tur ledde till syrebrist i vattenströmmarna. De nya kraven ledde till byggande av biologiska reningsverk, vars design togs från kommunala reningsverk. Kort efter de första biologiska reningsverken hade tagits i bruk i mitten av 1980-talet upptäckte man att den förväntade BOD-reningen inte kunde uppnås. I slutet av 1980-talet trädde begräsningar på kemisk syreförbrukning (COD) och fosfor (P) i kraft. COD lämpar sig bättre än BOD för styrning av biologiska reningsverk då det kan analyseras snabbare och mer exakt. I slutet av 1980-talet började skogsindustrin sluta vattenkretsloppen för att minimera mängden avfallsvatten och på sätt minska på byggkostnaderna för reningsverken. I början av 1990-talet konstaterade man att de nya kraven på COD var mycket svårare att nå än de tidigare kraven på BOD. Så småningom blev det klart att en del av analyserade COD-värden inte var nedbrytbart i det biologiska reningsverket. För den här delen började den engelska termen hard COD användas. Den del av COD som inte bryts ner biologiskt består främst av långkedjiga organiska molekyler eller toxiska ämnen. I denna avhandling presenteras fyra AOP-metoder för att behandla olika typer processvatten inom massa- och pappersindustrin. Gemensamt för AOP är in situ produktion av hydroxylradikaler. Fenton-processen är den mest kända AOP-tekniken. Fenton-processen grundar sig på användning av tvåvärt järn som metallkatalyt för att spjälka väteperoxid. I andra vanliga AOP används väteperoxid, ozon och UV bestrålning samt deras blandningar

Implementação e validação do método de determinação do carbono orgânico total em matrizes líquidas da indústria de pasta e papel

The pulp and paper (P&P) industry is one of the most important industries in the world and also one of the largest consumers of water. High water consumption implies the production of a high volume of effluents, being one of its characteristics the high concentration of organic compounds, which can have an environmental impact in the receiving aquatic systems, due to the decrease in the oxygen concentration. Chemical oxygen demand (COD) is widely used for monitoring the organic matter present in wastewater but, due to the production of hazardous wastes during the analysis, has increased the interest in replacing this method by total organic carbon (TOC). Following the acquisition of a TOC analyser by the RAIZ laboratory, the present study consisted in validating the direct method (NPOC) for TOC analysis. The evaluated parameters were the working range, linearity, sensitivity, limit of quantification (LQ) and precision. The factory working range, [0.3–3.0] μg was tested, having been the homoscedasticity condition of the data confirmed. The calibration curve, of the NPOC peak area as a function of NPOC weight, showed good linearity, proven statistically and by the correlation coefficient (r=0.99989). Sensitivity, assessed by the slope of the calibration curve, proved to be satisfactory. Also, the average slope deviation (4.9 %) from the factory slope was within the established acceptance criteria, i.e., 5 %. The quantification limit (LQ – 0.24 μg) proved to be appropriate for the method. The repeatability and intermediate precision (IP) were assessed for untreated and treated effluent. The former was acceptable for both matrices, with both CVr values below 10 %, 4.3 %, for untreated influent, and 8.9 %, for treated effluent. The repeatability limits were also defined for untreated (Δr=0.093 μg) and treated (Δr=0.071 μg) effluents. The IP was evaluated by range control charts, which showed that the process was under control for both types of samples. Reproducibility (CVR=8.2 %) was assessed through the participation in an interlaboratory test. The TOC consensus value of the wastewater sample was 91.9 mg/L and a Z-score of 0.12 was attributed to RAIZ. The uncertainty of the NPOC method was also calculated for both untreated (U=28.3 %) and treated effluent (U=22.3 %) matrices. Also, a study was carried out to establish COD:NPOC correlation factors for untreated and treated effluents from the P&P industry. The y=bx+a model was used to establish equations for both matrices, and b values of 3.02 and 2.36 were obtained, respectively. The validation of the difference method (DM) for TOC analysis was also started. However, the factory calibration proved not to be in effect and a new calibration was performed and properly validated by the analysis of a certified reference material. Finally, due to the total nitrogen (TNb) analysis capability of the TOC analyser purchased by RAIZ, the equipment was also calibrated for the surface waters matrix analysisA indústria da pasta e do papel (P&P) é uma das mais importantes do mundo e também uma das maiores consumidoras de água. Um elevado consumo de água traduz-se na produção de um elevado volume de efluentes, sendo uma das suas características a elevada concentração de compostos orgânicos, que podem ter um impacto ambiental negativo nos sistemas aquáticos recetores, devido à diminuição da concentração de oxigénio. A carência química de oxigênio (CQO) é usada para monitorizar a matéria orgânica presente nas águas residuais, mas devido à produção de resíduos perigosos durante a análise, tem aumentado o interesse na sua substituição pelo carbono orgânico total (COT). Após a aquisição de um analisador de COT pelo laboratório do RAIZ, o presente estudo consistiu em validar o método direto (NPOC) para análise de COT. Os parâmetros avaliados foram a gama de trabalho, linearidade, sensibilidade, limite de quantificação (LQ) e precisão. A gama de trabalho da fábrica, [0,3–3,0] μg foi testada, tendo-se confirmado a condição de homocedasticidade. A curva de calibração, da área do pico de NPOC em função da massa de NPOC, apresentou boa linearidade, comprovada estatisticamente e pelo coeficiente de correlação (r = 0,99989). A sensibilidade, avaliada pelo declive da curva de calibração, foi satisfatória. Além disso, o desvio médio do declive (4,9 %) relativamente ao de fábrica ficou dentro do critério de aceitação estabelecido, i.e., 5 %. O limite de quantificação (LQ - 0,24 μg) mostrou-se adequado para o método. A repetibilidade e a precisão intermediária (PI) foram avaliadas para as matrizes de efluente não tratado e tratado. A primeira foi aceitável para ambas as matrizes, com ambos os valores de CVr inferiores a 10 %, 4,3 % para efluente não tratado, e 8,9 % para efluente tratado. Os limites de repetibilidade foram também definidos para os efluentes não tratados (Δr=0,093 μg) e tratados (Δr=0,071 μg). A PI foi avaliada por cartas de controlo de amplitudes que mostraram que o processo estava sob controlo, para ambos os tipos de amostras. A reprodutibilidade (CVR=8,2%) foi avaliada através da participação num ensaio interlaboratorial. O valor consensual de TOC da amostra de água residual foi de 91,9 mg/L e um score-Z de 0,12 foi atribuído ao RAIZ. Além disso, a incerteza expandida (U) do método NPOC foi calculada para efluente não tratado (U=28,3 %) e efluente tratado (U=22,3 %). Foi realizado um estudo para estabelecer fatores de correlação COD:NPOC, para as matrizes de efluente não tratado e tratado, da indústria de P&P. O modelo do tipo y=bx+a foi usado para estabelecer equações para ambas as matrizes, tendo sido obtidos os valores de b de 3,02 e 2,36, respetivamente. A validação do método da diferença (DM) para análise de COT também foi iniciada no presente trabalho. No entanto, a calibração de fábrica provou não estar em vigor e foi realizada uma nova calibração que foi devidamente validada pela análise de um material de referência certificado. Finalmente, devido à capacidade de análise de azoto total ligado (TNb) do analisador de COT do RAIZ, o equipamento foi calibrado para a análise da matriz águas superficiaisMestrado em Biotecnologi

Using TiO2 to Optimize the Photocatalytic Degradation of Kraft Black Liquor Using Response Surface Methodology

The Canadian pulp and paper industry has been concerned with reducing annual emissions of pollutants into water bodies, air and landfills. Black liquor is a major byproduct from pulp mills such as Kraft. Black liquor is utilized in boilers to produce steam and electricity. Black liquor is a low-value chemical and researchers have employed thermal and chemical processes to produce products such as oils, adhesives, and dispersants. In recent years, photocatalysis has become an alternative to degrade black liquor into short chain carbon chemicals. This study aims to optimize the performance of black liquor photocatalytic degradation using the TiO2/UV system. Five practical factors were selected to develop the optimal total organic carbon (TOC) reduction. A two-level 2k design was used as the preliminary study for examining the optimal initial concentration of black liquor and TiO2. A three-level Box-Behnken design (BBD) with three factors that included pH, temperature, and particle size was then applied to further enhance the photocatalytic performance. The greatest TOC removal of 36.2±4.0% after 4 hours UV irradiation was obtained for 230 mg TS·L-1 black liquor and 2 g·L-1 TiO2. The black liquor concentration had larger impact on TOC removal in comparison with TiO2 concentration. A response surface methodology (RSM) model was developed to predict the maximum 4-hour TOC reduction of 51.6% under optimal conditions of a pH of 7.87, 37 ℃, and a catalyst particle size of 5 nm. Compared with the preliminary study, an additional improvement of 15% TOC removal efficiency was observed using the BBD

Interactions of chemical variations and biocide performance at paper machines

The objective of this thesis was to study the interactions of microbial activity, biocide usage and creation, and chemical changes in the papermaking process. The main focus was on oxidative biocide systems. In addition, new measurement and biocide production methods were applied to papermaking, and evaluated for the monitoring and control of the microbiological state and biocide usage. The measurement methods were based on portable handheld online equipments whereas the biocide production was based on electrochemical generation of biocides. The trials were mainly performed in pilot scale with actual process samples and complemented with a few laboratory trials. Most of the pilot results were verified in several field studies at paper machines. In the studies also the applicability of monitoring tools were evaluated. Biocide dosing itself, paper machine breaks, and poor management of broke generated chemical variations, which were detrimental to the papermaking process. Spoilage of broke due to poor broke management and poor biocide performance decreased the system pH, increased the conductivity, and caused the defects to the web. These chemical variations were also observed to cause variations in the cationic demand values. This probably caused unwanted particle flocculation generating the spots and holes to the web. Base paper defects were observed to cause runnability problems also at the coating machine. This cyclicity, where chemical variations cause breaks and breaks cause chemical variations, should be eliminated in order to restore good runnability. When revealing many such cause-effect relations and hidden phenomena, hand-held instrumentation gives additional references for existing basic measurements such as pH, conductivity, and redox potential. This work also took in use measurements which have not been traditionally used in papermaking such as measurement of halogens, dissolved calcium, and dissolved oxygen contents. ATP content measurement using a portable luminometer was found to be useful and easy-to-use method for evaluating microbial activity and optimizing biocide performance at paper mills. This thesis introduces a new biocide concept which can be used to prevent both microbial and biocidal problems described above. The results demonstrate how electrochemical on-site production can decrease chemical variations and improve biocide performance compared to current best practices offering an efficient and economically attractive alternative for microbial control

Mesophilic submerged anaerobic membrane bioreactor for pulp and paper secondary sludge treatment

The production of pulp and paper is associated with the generation of large quantities of wastewater that has to be purified to avoid severe pollution of the environment. Wastewater purification in pulp and paper mills uses sedimentation, biological treatment, chemical precipitation, flotation and anaerobic treatment, and the specific combination of techniques is determined by the local conditions. Wastewater treatment generates large volumes of organic solid waste (primary and secondary sludge) that after dewatering can be incinerated and thus used for bio-energy production. Sludge is currently viewed as biofuel of poor quality due to its high water content, and some mills treat it solely as a disposal problem. In this study, a new technology Submerged Anaerobic Digestion Membrane Bioreactor (SAnMBR) was developed in order to treat pulp and paper mill sludge, which can not only improve the quality of effluent after pretreatment, but also can recycle the value of PPMSS (pulp and paper mill secondary sludge). In this thesis, a laboratory-scale SAnMBR was operated for 330 days under 37 °C to explore the feasibility of PPMS treatment at different hydraulic retention times (HRTs), besides, alkali pretreatment was adopted to PPMS in order to explore its effects on performance of SAnMBR for the treatment, included biogas production, biogas yield, solids destruction ratio and effluent COD. COD removal efficiencies were all excellent (over 95%). The solids reduction ratio was in the range of 20%-50% and there was no significant difference in solids reduction ratio under different HRTs and alkali pretreatment. The biogas production rate decreased with an increase in HRT before and after alkali pretreatment had no significant impact on biogas production rate, and these two factors also influenced extracellular polymeric substances (EPS), soluble microbial products (SMP) and solids destruction ratio. Membrane performance was affected by PSDs of supernatant and SCOD, alkali pretreatment caused sludge deflocculation and a larger amount of fine colloidal flocs, which resulted in increasing of membrane fouling rate. However, the results shown that the biogas production in lower HRT was better comparing with it in higher HRTs, and quality of effluent was kept excellent during the experimental period, the pretreatment increased membrane fouling rate, and it had no significant effect on biogas production. SAnMBR was feasibility from this study, but membrane fouling should be an issue

Tratamento de águas residuais industriais com nanomateriais sintetizados para um ambiente sustentável

Quality of the final discharged effluents from industrial activities has been the subject of significant efforts over several decades to improve the performance of the methods applied for their treatment, either by physico-chemical, biological, or a combination of these processes. Among the emerging technologies, the application of various types of engineered nanomaterials (ENMs) has gained a particular attention in recent years. The present thesis aimed to carry out either experimental studies, surveys and critical reviews in order to synthesize the most sustainable nanomaterials for the treatment of recalcitrant pollutants from the content of industrial effluents. In parallel, the sustainability of other biological and physicochemical methods has been critically assessed and the most sustainable treatment methods have been suggested to be adopted by the industries. It was demonstrated in this thesis that the application of Tagguchi approach can considerably aid to control the properties of iron-based nanoscale particles synthesized by a liquidphase reduction process. Working with this system revealed that both the (reductant/Fe3+) ratio, (R), and the Fe3+concentration, [Fe3+], are the parameters that determine critical characteristics including particle crystalline phase composition, crystallinity and surface area although R has been revealed as the most important one. Nano zero valent iron particles with enhanced properties, synthesized by utilization of ultrasonic irradiation, was successfully tested to degrade organic dyes (methylene blue, as a case study) which are dominant in the wastewater from some industries such as textile factories. Recovery of the nanomaterials after being applied for the treatment purposes is also among the most important parameters for the selection and synthesis of the most sustainable nanomaterials for environmental applications. A novel ZnO/Fe3O4 on Bentonite nanocomposite prepared in this thesis showed acceptable photocatalytic decomposition of 2,4 dichlorophenol besides the ability to be recovered after being used. Magnetic nanocomposites were also tested for the degradation of AOXs from pulp and paper mill effluents and showed acceptable performance in such applications. A framework was also developed in this thesis for the sustainability assessment of the best available technologies to deal with industrial effluents, showing the efficiency of biological treatment methods to deal with industrial effluents although having some limitation to deal with phenolic industrial effluents. With a precise acclimatization process, very high efficiency for the biodegradation of phenol with a high degree of resistance to the shock of initial phenol concentration was achieved using activated sludge process. The results of a critical review, as the future outlook of this thesis, indicated the possibility of integration of engineered nanomaterials and also biological treatment with the membrane technologies in order to overcome the existing barriers for the rapid development of membrane technologies for the treatment of industrial effluents.A qualidade dos efluentes finais de atividades industriais tem sido, ao longo de várias décadas, objeto de esforços significativos para melhorar o desempenho dos seus métodos de tratamento, seja por via físico-química, biológica ou uma combinação destes. Entre as tecnologias emergentes, o recurso a nanomateriais sintetizados (ENMs) tem sido alvo de especial atenção nos últimos anos. A presente tese teve como objetivo realizar estudos experimentais, levantamentos de informação e revisões críticas, a fim de sintetizar nanomateriais sustentáveis para o tratamento de poluentes recalcitrantes existentes em efluentes industriais. Paralelamente, a sustentabilidade de outros métodos biológicos e físico-químicos foi avaliada criticamente, tendo-se sugerido os métodos de tratamento mais sustentáveis para serem adotados pelas indústrias. Foi demonstrado nesta tese que o recurso à abordagem de Tagguchi pode auxiliar consideravelmente no controlo das propriedades de partículas nanométricas à base de ferro, sintetizadas por um processo de redução em fase líquida. O estudo deste sistema revelou que tanto a razão (agente redutor/ Fe3+) como a concentração de Fe3+ são os parâmetros que determinam características críticas dos precipitados, incluindo a sua composição de fases cristalinas, grau de cristalinidade e área superficial específica. As nanopartículas de ferro de valência zero com propriedades melhoradas, sintetizadas pela utilização de irradiação por ultrasons, foram testadas com sucesso para degradar corantes orgânicos (azul de metileno como corante modelo) que são compostos dominantes nas águas residuais de algumas indústrias, designadamente de fábricas de têxteis. A recuperação dos nanomateriais após a sua aplicação em tratamentos de efluentes também é um dos aspectos mais importantes a ter em consideração na seleção e síntese de nanomateriais sustentáveis para aplicações ambientais. Um novo nanocompósito de ZnO/Fe3O4 sobre Bentonite, produzido neste trabalho, revelou uma capacidade aceitável para decomposição fotocatalítica do 2,4 diclorofenol, além da capacidade de ser recuperado após utilização. Testaram-se também nanocompósitos magnéticos na degradação de AOXs de efluentes da indústria do papel e celulose que evidenciaram um desempenho aceitável nessas aplicações. Definiu-se também nesta tese um contexto para a avaliação da sustentabilidade das melhores tecnologias disponíveis para lidar com efluentes industriais, tendo-se revelado a eficiência dos métodos de tratamento biológico para lidar com efluentes industriais, embora com alguma limitação para lidar com efluentes industriais fenólicos. Com um processo de aclimatação preciso, conseguiu-se uma eficiência muito elevada para a biodegradação do fenol, com alto grau de resistência ao choque da concentração inicial de fenol, utilizando-se o processo de lamas ativadas. Mediante uma revisão crítica da literatura, e como perspectivas de futuro a extrair do presente trabalho, aponta-se a possibilidade de integrar nanomateriais sintetizados e tratamento biológico nas tecnologias de membrana, para superar as barreiras actualmente existentes ao rápido desenvolvimento das tecnologias de membrana para o tratamento industrial efluentes.Programa Doutoral em Ciências e Engenharia do Ambient

Combined biological and advance oxidation processes for paper and pulp effluent treatment

A thesis submitted in fulfilment of the requirements f Master of Science in Engineering to the School of Chemical and Metallurgical Engineering, Faculty of Engineering, University of the Witwatersrand, Johannesburg, 2017Recently, the South African paper and pulp industry has become increasingly interested in the development of suitable wastewater treatment technologies able to assist in the closure of the water network and also to minimize their environmental footprint at their sites. Factors such as the rising cost of fresh water, stricter environmental legislation and socio-political pressure have forced water intensive users to become less dependent on the municipalities. The research described here addresses wastewater problems from two separate mills. Mill X (Case A) is relying on the municipality for fresh water and the treatment of their effluent. The mill wants to become less dependent on the municipality by closing the water network (zero effluent discharge). A wastewater treatment plant (WWTP) would be required to reduce the chemical oxygen demand (COD), total suspended solids (TSS) and colour before any processes water could be reused. Mill Y (Case B) is currently using their effluent for the irrigation of the local plantation. The mill would like a wastewater treatment plant able to reduce the biodegradable material prior to irrigation. Excessive amounts of biodegradable organics in the effluents can cause bacterial and fungal growth in the irrigations systems and consequently clogging problems. More advanced treatment steps would also be required to lower the bio-recalcitrant COD to environmental discharge limits (<400 mg/L). As a result, this study investigated the potential of combining biological and advanced oxidation processes (AOP) for effluent treatment at both mill effluents. An extensive literature study on the treatment of paper and pulp mill effluents was conducted to get a comprehensive understanding of the treatment technologies/combinations. The treatment of paper and pulp mill effluents can be divided into three distinct treatment stages namely: Primary treatment: For the removal of the total suspended solids (TSS) Secondary treatment: For the removal of the biochemical oxygen demand (BOD) Tertiary treatment: Mainly for the removal of bio-recalcitrant chemical oxygen demand (COD) and colour Mill X and Mill Y already contained primary clarifiers to remove the majority of the total suspended solids (TSS). Consequently, the secondary and tertiary treatment steps were evaluated. A detailed technology selection assessment was done to select the best suited secondary and tertiary treatment technologies for the purpose of this project. The work demonstrated that an aerobic MBBR could be used in combination with Fenton related treatment technologies in order to comply with the individual mill specifications. The applicability of both these biological and AOP treatment solutions was therefore extensively investigated. The results indicated that the aerobic moving bed biofilm reactor (MBBR) was able to remove the majority of the biodegradable organics from the recycle and neutral semisulfite chemical pulping mill effluents. The optimal COD removal efficiency ranged between 46% and 57% for the various effluents. The effluent from Mill X was generally found to be more readily biodegraded than the effluents from Mill Y. Experimental results indicated that certain effluents contain organics that display antimicrobial properties. The maximum substrate removal rate decreased linearly with an increase in phenols. As a result, it was therefore assumed that lignin derived alkyl phenols might have inhibited aerobic and anaerobic microbial digestion processes. The results indicate that the MBBR system was not fully acclimatized for high phenolic wastewaters. It is therefore recommended that future experimental studies consider the effects of phenolic content and employ longer acclimatization periods. A significant fraction of the paper and pulp mill effluents were considered to be bio-recalcitrant and required tertiary treatment to be removed. It was found that both the Fenton (Fe3+/H2O2) and Fenton-like (Fe3+/H2O2) oxidation processes can remove bio-recalcitrant organics from biologically treated mill effluents (BTME). However, preliminary experimental results indicated that the Fenton process had a faster oxidation rates. For the Fenton process, the optimal COD removal efficiencies ranged between 40% and 67% for the BTMEs. The experimental results also demonstrated that a combination of Fenton oxidation and slaked lime treatment can effectively remove the colour of BTMEs (97%). The COD removal rates for the neutral sulfite semi-chemical (NSSC) effluents were found to be higher than that of the recycle mill effluent (RME). The aromatic and volatile organic acid (VOA) content of the BTMEs had an important role in the oxidizing processes. The BTMEs with a higher volatile organic acid (VOA) content generally had slower oxidizing rates. The experimental results indicated that the combination of an aerobic MBBR and Fenton process can be implemented at both paper and pulp mills to assist with their individual treatment requirements. An economic study for Case A (Mill X) was also conducted. The data obtained throughout this study was linked to previous water optimization work done at the mill. The economic analysis demonstrated that the aerobic moving bed biofilm reactor (MBBR) and Fenton treatment combination could treat the recycle mill effluent for reuse in a cost-effective manner. The total capital investment cost of the treatment plant was estimated to be R28.5 million and the operational cost was found to be R12.21/m3 of wastewater. The implementation of this treatment solution on the water network could save the mill approximately R 1.25 million/year. The rising cost of fresh water and discharge might increase the economic feasibility of such a WWTP in the near future.XL201

Application of membrane filtration in system closure of white water systems in newsprint mills.

M. Sc. Eng. University of KwaZulu-Natal, Pietermaritzburg 2015.The pulp and paper industry is considered to be one of the most water intensive industries in S.A. With increasing environmental regulations and awareness the industry is leaning towards system closure. By recycling water and using it back in the process, the industry can considerably reduce its consumption of fresh water as well as its production of waste water. One method that is gaining momentum for the purification of water is membrane filtration. Membrane filtration does not require any sophisticated heat-generating equipment as compared to conventional separation methods like evaporation making it a viable choice. It is, however, prone to fouling and requires long membrane cleaning cycles. The first part of the study involved the simulation of system closure in the laboratory using a Rapid-Kothen sheet forming machine. This was conducted in order to determine the accumulation of the different contaminants as the white water is recycled. Results obtained indicate that the accumulation of contaminants with increasing number of cycles tends to exhibit a linear relationship. The burst index and brightness of the paper decreased as the level of closure increased. The main aim of the project was to evaluate ultrafiltration as the core process for purification of white water in terms of productivity, retention, flux decline, fouling and cleanability of the membrane as well as to determine the optimum operating conditions that reduce fouling. Polymer membranes having different molecular weight cut offs (10, 50, 100 and 150 kDa) were tested. Overall it was established that the 100 kDa membrane exhibited the lowest degree of irreversible fouling, the best cleanability, the highest productivity and average permeate flux and the permeate obtained from this membrane met most of the water quality requirements for the reuse of water in the paper manufacturing process. The 100 kDa membrane was used in further studies. The optimum operating conditions that reduce fouling was determined using the Taguchi method. Three parameters were investigated at three levels i.e. temperature (20, 40 and 60°C), pressure (1,2 and 3 bar) and volume reduction factor (VRF) (0.63, 0.71 and 0.86). Results obtained indicated that low temperatures, pressures and VRF values reduced the fouling hence the optimum operating conditions were a temperature of 20°C, a pressure of 1 bar and a VRF of 0.63. The permeate quality obtained at the optimum conditions is in accordance with the water quality standards for the reuse of water in the process. Alum and FeCl3 coagulation were used as pre-treatments to ultrafiltration to reduce the membrane fouling thereby increasing the membrane life. Results obtained indicate that twice as much FeCl3 than alum is required to obtain a similar reduction in suspended solids and turbidity and a low sludge volume index (SVI). FeCl3 is more expensive than Alum; requiring twice as much would considerably increase the cost of treatment. Hence alum was chosen as the coagulant to be used in further tests. It was found that the optimum dosage and pH were 288.8 mg/L and 7.68 respectively