Process regime classification and modelling of a sequencing batch reactor for producing polyhydroxybutyrate with mixed culture using neural networks

PhD ThesisIn recent years, there has been a growing incentive towards production and application of environmentally benign materials with properties similar to those obtained from irreplaceable resources or exhibiting harmful effects on the environment. In this respect, bioplastics have gained attention in quest of materials that can be used in place of conventional petro-chemical plastics. Biocompatibility, biodegradability and compostability of bioplastics are among the most favourable characteristics of the materials mostly derived from biological systems. Polyhydroxybutyrate (PHB) is a fully biodegradable bioplastic with similar physical properties to polyethylene and promising applications in various commercial fields including automation, aviation, medication, nutrition, fuel, packaging and many more. PHB production with Mixed Microbial Cultures (MMC) has recently gained attention as a cost effective production strategy by using bacteria that adapt with complex substrates presented in inexpensive waste materials. The initial research motivation was to enhance PHB production operation by means of the solutions obtained from sophisticated mathematical algorithms used for process optimisation. For this aim, a computer-based program simulating PHB batch process with MMC which was successfully validated with experimental data was available. Since mechanistic models of the simulation program could not be applied in optimisation algorithms, accurate empirical models were required. In the quest for reliable and accurate empirical models that can predict product concentration at the final stage of a batch operation, a methodology was developed in this study for classification of the batch operational regions based on the PHB critical process attributes. In the core of this research work, an innovative systematic methodology improves process understanding towards advanced process monitoring and control. This method enables operational scrutiny for generation of process knowledge regarding PHB process using MMC. The qualitative info-illustrations produced in the course of the classification method provide a sound platform for generation of considerably more accurate (quantitative) empirical models. These empirical models will be used in process optimisation studies. Abstract III In this research, PHB production occurs in a process type known as “feast and famine” or as “aerobic dynamic feeding” which is a well-known strategy applied for bacterial production with MMC. The “feast and famine” operations take place in Sequential Batch Reactors (SBR) in order to assure occurrence of the “feast” and the “famine” phases intermittently in each operational cycle. While PHB formation occurs during the “feast” phase, a “famine” phase should be followed to cause a cell physiological adaptation to maintain PHB production capability of bacteria. Establishment of the analytical methodology developed in direction of process empirical modelling realisation enables prediction of “feast” and “famine” phase occurrences based on the batch initial state documented for the first time in this work. This mathematical equation (“Phase Differentiating Equation”) plays a significant role in development of a novel SBR recipe for production of PHB with MMC. Execution of the recipe by the PHB process simulation program demonstrates high reliability of the proposed recipe. Application of the “Phase Differentiating Equation” in the SBR recipe assures favourable occurrence of the “feast” and “famine” phases in the majority of operational cycles. Reduction of operational failure rate reduces PHB production cost to improve its market position. The SBR recipe structure consists of six-stage cycles including (1) “feast” phase preparation stage, (2) “feast” phase operation, (3) operational quiescence, (4) product exploitation, (5) “famine” phase preparation stage and (6) “famine” phase operation. Operational reliability is investigated along with load disturbance rejection embedded in the SBR recipe. At the end, Sequential Quadratic Programming (SQP) is applied successfully as an optimisation algorithm to maximise PHB production under operational constrains

Utilization of Poly(Polyvinyl Alcohol-g-2-Ethylhexyl Acrylate) as Admixture for Mortar

We investigated the physico-mechanical properties of mortar mixed with copolymers based on polyvinyl alcohol (PVA) and 2-ethylhexyl acrylate (2-EHA) and synthesized by grafting using ammonium persulfate (APS) as an initiator. Increasing the amount of 2-EHA in the copolymer from 4% to 8% reduced the water/cement (W/C) ratio, the initial and final setting times, and the water absorption of mortar, while it increased its compressive strength.<br/

Distribution, Abundance And Biomass Of Phytoplankton In The Southern Part Of Caspian Sea (In Iranian Waters) [QK933. A398 2007 f rb].

Kajian penyebaran bermusim fitoplankton dan parameter fiziko-kimia di Lautan Caspian telah dijalankan di 6 transek, 26 stesen pada kedalaman 0 meter (permukaan), 5, 10, 20, 50 dan 100 meter. Sejumlah 260 sampel fitoplankton telah dikumpulkan daripada strata kolum air semasa persampelan di sepanjang pesisir pantai (bahagian selatan) Lautan Caspian. Seasonal distribution of phytoplankton and the physico-chemical parameters of the Caspian Sea were investigated at 6 transects with 26 stations, at the depths of surface 5,10, 20, 50 and 100m from winter (January-February), spring(May), summer(July), autumn (October-November) in 2005. A total of 260 phytoplankton samples were collected from the stratified water column during the sampling along Iranian coasts (southern part ) of the Caspian Sea

Nonconventional Ca(OH) ₂ treatment of bamboo for the reinforcement of cement composites

This study compares the structural and morphological changes in Guadua angustifolia Kunth (GAK) fiber prepared in three different ways (chips, barkless and crushed) when non-conventional alkaline treatment is applied. Moreover, it shows the improvement of mechanical properties of cement composites reinforced with these treated fibers. The three different preparations of Guadua were treated with a saturated solution of calcium hydroxide (5%) at 125 &deg;C and 1.25 kPa for 3 h to remove non-cellulosic compounds. Then, their chemical, morphological, and structural properties were examined. The fibers exhibiting the higher delignification rate were selected to prepare cement composite boards, whose mechanical properties were successively compared with those of composites reinforced with untreated G. angustifolia fibers. The water/cement ratios of the cement mixed with the Ca(OH)2-treated and the untreated fibers were, respectively, around 0.3 and 0.25. The flexural strength and toughness of the two composites were evaluated after 7, 28, and 90 days of curing. The calcium hydroxide treatment showed higher efficiency in removing non-cellulosic materials when performed on crushed bamboo; moreover, the mechanical properties of the composites reinforced with the treated fibers were higher than those mixed with the untreated ones. After 90 days of curing, the flexural strength increased by around 40% and the toughness became three times higher (p &lt; 0.05). The mechanical improvement by the Ca(OH)2 treatment of G. angustifolia fibers demonstrates its potential for the fabrication of cement composites

The impact of variation in chemical and physical properties of PFA and BPD semi-dry cement paste on strength properties

The effect of Pulverised Fuel Ash (PFA) and By-Pass-Dust (BPD) in ternary semi-dry cement pastes was reported. As well as this, the variability over 6 months in chemical composition and particle distribution was reviewed to determine impact on strength. The addition of BPD in ternary pastes resulted in a reduced strength when combined with PFA. PFA and BPD samples obtained over a 6 month period showed variability in both chemical composition and particle distribution. For PFA, it was reported that at 14 days the particle size distribution had greatest impact on strength and at 28 days the SiO2 content had greatest impact. The high variability in BPD particle size distribution resulted in finer particles achieving the greatest strength

Distribution pattern of phytoplankton (Chrysophyta and Pyrrophyta) in the southern Caspian Sea

In regard to study the distribution pattern of phytoplanktons (with emphasize on chrysophyta and pyrrophyta), a series of 4 cruises were carried out seasonlly in 1996. A total of 93 species belong to 2 main phyllums of chrysophyta (mainly diatoms) and pyrrophyta were identified consist of73 and 20 species, respectively. The diatoms have an important role in the whole Caspian Sea from point of species diversity and on the other hand contain the most abundance and biomass in all seasons. There are two main species of Rhizosolenia calcaravis (belong to chrysophyta) and Exuviealla cordata (from Pyrrophyta) inhabit in the southern Caspian Sea. Comparing the density and biomass of different phyllums of phytoplanktons showed that chrysophyta with 75% and pyrrophyta with 17% are the most abundant phytoplanktons in the said region