Removal of ametryn using membrane bioreactor process and its influence on critical flux

Compared to the Conventional Activated Sludge Process (ASP), Membrane Bioreactors (MBRs) have proven their superior performance in wastewater treatment and reuse during the past two decades. Further, MBRs have wide array of applications such as the removal of nutrients, toxic and persistent organic pollutants (POPs), which are impossible or difficult to remove using ASP. However, fouling of membrane is one of the main drawbacks to the widespread application of MBR technology and Extra-cellular Polymeric Substances (EPS) secreted by microbes are considered as one of the major foulants, which will reduce the flux (L/m2/h) through the membrane. Critical flux is defined as the flux above which membrane cake or gel layer formation due to deposition of EPS and other colloids on the membrane surface occurs. Thus, one of the operating strategies to control the fouling of MBRs is to operate those systems below the critical flux (at Sub-Critical flux). This paper discusses the critical flux results, which were obtained from short-term common flux step method, for a lab-scale MBR system treating Ametryn. This study compares the critical flux values that were obtained by operating the MBR system (consisting of a submerged Hollow-Fibre membrane with pore size of 0.4μm and effective area of 0.2m2) at different operating conditions and mixed liquor properties. This study revealed that the critical flux values found after the introduction of Ametryn were significantly lower than those of obtained before adding Ametryn to the synthetic wastewater. It was also revealed that the production of carbohydrates (in SMP) is greater than proteins, subsequent to the introduction of Ametryn and this may have influenced the membrane to foul more. It was also observed that a significant removal (40-60%) of Ametryn from this MBR during the critical flux determination experiments with 40 minutes flux-step duration.

Coagulation and nano-filtration: a hybrid system for the removal of lower molecular weight organic compounds (LMWOC)

The removal of lower molecular weight organic compounds (LMWOC) from water is of increasing concern. While, nano-fi ltration (NF) is a good option, it removes only a fraction of the LMWOC. In this paper, NF experiments were conducted to remove oxalic acid and diuron in combination with coagulation using poly-aluminum chloride (PAC) as the coagulant. The results showed that this hybrid treatment system was effective in removing oxalic acid where almost a 100% removal effi ciency of oxalic acid was achieved. However, using PAC as coagulant to remove diuron from water was not effective. In order to improve the removal efficiency of diuron, 0.02 M NaCl was added to diuron and a 40% increase in the removal of diuron was achieved. Higher removal of diuron was achieved when the solution was treated with reverse osmosis (RO) when compared to the nano-filtration.

Pretreatment of seawater for biodegradable organic content removal using membrane bioreactor

Reverse osmosis (RO) is currently one of the most prevalent methods used for seawater desalination. During the past four decades, the research anddevelopment has reduced the energy consumption from about 20 to 4 kWh/m3, while improvements in membrane science has led to a 20-fold increase in the specific membrane flux. Nevertheless, research is still underway to reduce the operation and maintenance problems and thus improve the performance of RO systems. The most important maintenance problem associated with RO operation is the membrane fouling, especially biological fouling (biofouling). This work focuses on the aspects to eliminate biofouling in RO membranes, by adopting a proper pretreatment system. The experimental results revealed that fluidized bed biological granular activated carbon, at 15 min empty bed contact time (with dissolved organic carbon, DOC concentration of 6–8 mg/L) can be utilized effectively to remove nearly 100% biodegradable DOC from seawater. Continuous experiments of membrane bioreactor (MBR) have been conducted concomitantly to gain insight into the long-term effects of MBR on biodegradable organic content removal and biofouling control. The results show that MBR system produced better effluent with 78% DOC removal and quasi-total biodegradable DOC removal. Dissolved oxygen was not a limiting factor for the DOC degradation. Short-term experimental runs were conducted with RO membrane using both pretreated and non-pretreated seawater. The results showed that filtrate from MBR yielded the highest permeate flux improvement, which was approximately 300% compared with non-pretreated seawater.

Effect of natural organic compounds on the removal of organic carbon in coagulation and flocculation processes

Natural organic matter (NOM) in water contains organic compounds that are both hydrophobic and hydrophilic with a wide range of molecular weights. It is composed of non-homogeneous organic compounds such as humic substances, amino acids, sugars, aliphatic and aromatic acids, and other chemical synthetic organic matters. NOM in water is a major concern not only because of its contribution to the formation of disinfection by-products (DBPs) and taste and odor, but also its influence on the demand for coagulants and disinfectants, the removal efficiency of water treatment processes, etc. This research aims at identifying the influence of NOM in coagulation and flocculation processes in order to optimize the coagulation and flocculation conditions. In this study, pretreated pond water was used as the source water. It was observed from the experimental results that: (1) The optimum pH for coagulation to remove NOM is around 7. (2) The optimum alum dose at this pH can vary from 125-1,225 mgl-1 when the TOC is increased from 4 to 25 mgl-1. (3) The presence of secondary compounds such as Ca2+, Mg2+ divalent cations had no significant effect on the removal of organic matter. (4) The presence of clay increased the organic removal by 15%. (5) The organic compound with higher molecular weight has higher removal affinity in coagulation process. (6) Floc size and settling velocity of floc and sludge production all increased with the increase in NOM concentration. From the results of Capillary Suction Time (CST) tests, the floc formed with lower TOC readily released the water to make the dewatering process easier. (7) The organic removal efficiency was significantly different for natural water containing non-homogeneous organic compounds compared to the synthetic water containing humic acid only (homogeneous organic matter). For example, the NOM removal efficiency was 80% for the synthetic water containing humic acid with TOC of 7 mgl-1 at pH 7; but the NOM removal for the pretreated pond water was 60%.

Matching objects across the textured-smooth continuum

The problem of 3D object recognition is of immense practical importance, with the last decade witnessing a number of breakthroughs in the state of the art. Most of the previous work has focused on the matching of textured objects using local appearance descriptors extracted around salient image points. The recently proposed bag of boundaries method was the first to address directly the problem of matching smooth objects using boundary features. However, no previous work has attempted to achieve a holistic treatment of the problem by jointly using textural and shape features which is what we describe herein. Due to the complementarity of the two modalities, we fuse the corresponding matching scores and learn their relative weighting in a data specific manner by optimizing discriminative performance on synthetically distorted data. For the textural description of an object we adopt a representation in the form of a histogram of SIFT based visual words. Similarly the apparent shape of an object is represented by a histogram of discretized features capturing local shape. On a large public database of a diverse set of objects, the proposed method is shown to outperform significantly both purely textural and purely shape based approaches for matching across viewpoint variation.

The nature and scope of rights of removal

The rationale underlying the fixtures and accession presumptions is the need to protect the value of the chattel as well as the need to protect third-party interests. The destruction of the independent legal status of an attached chattel is generally deemed appropriate where the value of the co-mingled asset will be diminished if the chattel retains a separate legal title and this would generate unfairness because third parties have dealt with the co-mingled asset on the basis of its overall value. Rights to remove have evolved under both common law and equity to moderate the scope of these presumptions. Common law will uphold the right of a tenant to remove chattels that have been attached to leased premises during the currency of the lease. Equity on the other hand will uphold the right to remove affixed chattels in circumstances where the enforcement of such an entitlement is consistent with contractual intention and transactional fairness. This article examines the different rights of removal that have evolved under Australian law to date and the emergent statutory framework supporting these rights. It discusses the historical purpose and structural utility of these entitlements within a land framework that supports fixtures presumptions. Rights of removal, whether validated at law or in equity, confer positive entitlements upon the holder to access and remove affixed goods in circumstances where, because of the fixtures and accession presumptions, those goods no longer retain any separate legal status. The capacity of the holder to enforce this right against third parties is illustrative of their distinctive proprietary perspective.