Integrated water treatment: softening and ultrafiltration

textIntegrated water treatment with softening and ultrafiltration is proposed as a promising option for hard waters, as a means to balance risks from microorganisms and disinfection/disinfectant by-products in drinking water systems. The biggest impediment for applying membrane processes is to control fouling. Therefore, the objectives of this research were to understand the nature of the fouling mechanisms for ultrafiltration when used for hard waters and to use that understanding to determine options for the use of softening as a pretreatment before ultrafiltration. To understand fouling mechanisms in the integrated system, three conditions in softening were selected: standard softening, enhanced softening, and Mg softening conditions based on results from two natural waters (i.e., Lake Austin water and Missouri River water). Each condition corresponded to three different levels of softening performance in terms of removal of inorganics and organic matter. Experiments were performed using both the natural waters and synthetic waters with similar (but separable) inorganic, organic, and particulate characteristics. Based on their behavior in softening, alginic acid and dextran with nominal molecular weight of 60 kD were chosen as reasonable surrogates for natural organic matter (NOM). Four possible fouling mechanisms were investigated: inorganic fouling by precipitates, organic fouling, particle fouling, and combined fouling by particle and organic matter. The organic fouling and the combined fouling by particle and organic matter were the major fouling mechanisms. The integrated treatment with softening and ultrafiltration proves to be a promising option for hard waters since softening pretreatment effectively reduced the foulants prior to ultrafiltration. The degree of softening to improve water flux should be determined with the raw water to be applied because it depends on the raw water characteristics. Fouling was investigated with flux decline and extents of recovery by three different cleaning methods. Surface analyses of fouled membranes were performed with scanning electron microscopy and X-ray photoelectron spectroscopy.Civil, Architectural, and Environmental Engineerin

2(5H)-Furanone: a prospective strategy for biofouling-control in membrane biofilm bacteria by quorum sensing inhibition

Biofouling of membranes demands costly periodic cleaning and membrane replacement. A sustainable and environmentally friendly solution for maintenance is not available and would be of great interest for many purposes including economical. As complex biofilm formation by environmental strains is the major cause of biofouling and biofilm formation in most cases are controlled by N-Acylhomoserine lactone (AHL)mediated Quorum Sensing (QS). An effort was made to understand the appropriateness of 2(5H)-furanone, to use against biofouling of membranes. QS inhibition activity by 2(5H)-furanone was studied using bioindicator strains and known AHLs of different acyl chain lengths. The biofilm inhibition was studied by growth analysis on polystyrene plate of Aeromonas hyrdrophila, an environmental biofilm strain isolated from a bio-fouled reverse osmosis (RO) membrane. Results showed a QS inhibition activity against a wide range of AHLs and also biofilm formation by 2(5H)-furanone, which is believed to act as a potential quorum inhibition agent in a bacterial biofilm community

Styrene-Based Copolymer for Polymer Membrane Modifications

Poly(vinylidene fluoride) (PVDF) was modified with a styrene-based copolymer. The crystalline behavior, phase, thermal stability, and surface morphology of the modified membranes were analyzed. The membrane surface roughness showed a strong dependence on the styrene-acrylonitrile content and was reduced to 34% for a PVDF/styrene-acrylonitrile blend membrane with a 40/60 ratio. The thermal and crystalline behavior confirmed the blend miscibility of both polymers. It was observed in X-ray diffraction (XRD) experiments that the modified PVDF membranes show a drastic reduction in their crystallinity. The neat PVDF membrane has the highest degradation rate, which decreased with the addition of the styrene-based copolymer

Silicon optrode array with monolithically integrated SU-8 waveguide and single LED light source

Objective. This paper presents a conventional light emitting diode (LED) and polymer waveguide coupled silicon optrode array. Approach. Unique lens design at the waveguide inlet enables a high light coupling efficiency with a single LED light source, and provides small power consumption compatible with a wireless optogenetic neuromodulation system. To increase the light intensity at the waveguide tip, a lensed waveguide is fabricated with epoxy-based photoresist SU-8, which has a plano-convex lens shape at the waveguide inlet to focus the light in the horizontal direction. In addition, a cylindrical lens is assembled in front of the waveguide inlet to focus the source light in the vertical direction. Main results. The glass cylindrical lens and SU-8 plano-convex lens increased the light coupling efficiency by 6.7 dB and 6.6 dB, respectively. The fabricated 1 x 4 array of optrodes is assembled with a single LED with 465 nm wavelength, which produces a light intensity of approximately 2.7 mW mm(-2) at the SU-8 waveguide outlet when 50 mA input current is applied to the LED. Each optrode has four recording electrodes at the SU-8 waveguide outlet. The average impedance of the iridium oxide (IrO (x) ) electroplated recording electrodes is 43.6 k omega. Significance. In-vivo experiment at the hippocampus region CA1 and CA2 demonstrated the capability of optical stimulation and neural signal recording through the LED and SU-8 waveguide coupled silicon optrode array.N