Deposition of submicron particles in deep bed filtration under unfavorable surface conditions

Deterioration in the filter removal efficiency of submicron particles (λ/λ_o) under unfavorable surface conditions is affected by the number of deposited particles per filter grain. In the case of above micron particles, the deterioration of filter removal efficiency has been mainly due to the blocking effect of deposited particles and not by the number of deposited particles. Deposition of large number of submicron particles changed the surface characteristics of collectors (filter grain associated with deposited particles) and enhanced unfavorable surface conditions. Filtration experiments were conducted with monodispersed suspensions of known sizes of submicron latex particles at different ionic strengths, using glass beads as filter grains. The filtration performance was predicted by using a mathematical model, assuming a linear relationship between λ/ λ_o and Σ (i.e. λ/λ_o=1 − kΣ). For both particles, k was found to decrease andλ _o was found to increase with the increase in the ionic strength. A comparison was made of the importance of blocking effect for the filtration of submicron particles.     

Urban stormwater quality and treatment

Stormwater runoff from urban and suburban areas generates numerous pollutants. The areas include residential areas, parks, commercial areas, industrial areas and road/highways. Land use and human activities largely determine the nature and level of pollutants. Among the various types of pollutants that can contribute to adverse water quality impact in receiving water bodies, of concern are suspended solids, heavy metals, polycyclic aromatic hydrocarbons and nutrients. This paper provides a critical review of the characteristics and sources of urban stormwater pollutants and the manner in which the pollution occurs. Treatment systems for urban stormwater runoff and for urban stormwater harvesting are discussed.     

The integral divalent cation within the intermolecular purine*purine. pyrimidine structure: a variable determinant of the potential for and characteristics of the triple helical association

In vitro assembly of an intermolecular purine*purine.pyrimidine triple helix requires the presence of a divalent cation. The relationships between cation coordination and triplex assembly were investigated, and we have obtained new evidence for at least three functionally distinct potential modes of divalent cation coordination. (i) The positive influence of the divalent cation on the affinity of the third strand for its specific target correlates with affinity of the cation for coordination to phosphate. (ii) Once assembled, the integrity of the triple helical structure remains dependent upon its divalent cation component. A mode of heterocyclic coordination/chelation is favorable to triplex formation by decreasing the relative tendency for efflux of integral cations from within the triple helical structure. (iii) There is also a detrimental mode of base coordination through which a divalent cation may actively antagonize triplex assembly, even in the presence of other supportive divalent cations. These results demonstrate the considerable impact of the cationic component, and suggest ways in which the triple helical association might be positively or negatively modulated.     

A combined photocatalytic slurry reactor–immersed membrane module system for advanced wastewater treatment

Photocatalysis with titanium dioxide semiconductor catalyst can effectively degrade recalcitrant organic pollutants present in biologically treated sewage effluents. Focusing on process efficiency and sustainability within a broader program, this study presents results obtained with a bench-scale hybrid treatment system. The process train comprised of a slurry (suspension) type continuous photocatalytic (CP) system and an immersed hollow fibre membrane micro-ultrafilter (MF/UF) unit. The CP reactor charged with 1 g/L P-25 catalyst removed 63% dissolved organic carbon (DOC) from a synthetic wastewater (representing biologically treated sewage effluent). The addition of 0.05 g/L of powdered activated carbon (PAC) increased DOC removal up to 76%. The start-up times to achieve 60% DOC removal were 31 min and 15 min, respectively. These results show a 16 times improvement in volumetric load over a comparable batch reactor system used in previous studies by our group.Slurry type photocatalytic reactors need subsequent particle separation to retain the catalyst in the system and allow the discharge of treated effluent. The immersed membrane module accomplished this without prior slurry settling step. Membrane feed pre-treatment with pH adjustment and particle charge neutralisation with aluminium chloride coagulant led to improved critical membrane fluxes, 15.25 L/m² h and 19.05 L/m² h, respectively. In each experiment MF/UF produced near zero turbidity permeate, completely retained the photocatalyst, and flocculation also improved the efficiency of DOC removal. Membrane fouling was controlled by particle aggregation rather than feed DOC levels, but the latter had significant impact on coagulant demand. The complete treatment train achieved up to 92% DOC reduction with 12 mg/L AlCl₃ dosage using in-line coagulation conditions. The results show that in-line coagulation offers a simple yet effective means to improve the performance of slurry type photocatalytic–MF/UF hybrid systems for advanced water and wastewater treatment applications.     

A hybrid approach for the optimization of quality of service metrics of WSN

The core objective behind this research paper is to implement a hybrid optimization technique along with proactive routing algorithm to enhance the network lifetime of wireless sensor networks (WSN). The combination of two soft computing techniques viz. genetic algorithm (GA) and bacteria foraging optimization (BFO) techniques are applied individually on destination sequence distance vector (DSDV) routing protocol and after that the hybridization of GA and BFO is applied on the same routing protocol. The various simulation parameters used in the research are: throughput, end to end delay, congestion, packet delivery ratio, bit error rate and routing overhead. The bits are processed at a data rate of 512 bytes/s. The packet size for data transmission is 100 bytes. The data transmission time taken by the packets is 200 s i.e. the simulation time for each simulation scenario. Network is composed of 60 nodes. Simulation results clearly demonstrates that the hybrid approach along with DSDV outperforms over ordinary DSDV routing protocol and it is best suitable under smaller size of WSN.

     

Performance evaluation and mathematical modelling of granular activated carbon biofiltration in wastewater treatment

Biological filtration is an effective technique for removing organic matter from wastewater. The performance of a biofilter can be influenced by a range of operational conditions. In this study the performance of biofilters was investigated for the influence of filter media depth, influent concentrations, filtrations rates and backwashing. The results show that performance of GAC filters decreased with shallower filter bed depths. In addition, the GAC performed better at lower influent concentration and lower filtration rates. The daily backwash adopted to avoid the physical clogging of the biofilter did not have any significant effect on the organic removal efficiency of the filter. The concentration, activity and characteristics of the biomass are quantified and described. A mathematical model was developed to simulate the organic removal of the GAC biofiltration system. The performance of the GAC filter under different influent organic concentration levels, filtration rates and filter bed depths was adequately simulated by the mathematical model developed for this study.     

Determination of rate constants and half-lives for the simultaneous biodegradation of several cyanobacterial metabolites in Australian source waters

The fate of five cyanobacterial metabolites was assessed in water sourced from Lake Burragorang (Warragamba Dam) in New South Wales, Australia. All of the studied metabolites were shown to be biodegradable in this water source. For some metabolites, biodegradation was influenced by factors, including temperature, location (within the water body) and seasonal variations. The biodegradation of the metabolites was shown to follow pseudo-first-order kinetics with rate constants ranging from 8.0 × 10⁻⁴ to 1.3 × 10⁻² h⁻¹. Half-lives of the metabolites were also estimated and ranged from 2.2 to 36.1 d. The order of ease of biodegradability in this water source followed the trend: microcystin-LR ≥ cylindrospermopsin > saxitoxins > geosmin ≥ 2-methylisoborneol. The lack of detection of the mlrA gene during microcystin biodegradation suggests that these toxins may be degraded via a different pathway. While no metabolite-degrading organisms were isolated in this study, the inoculation of previously isolated geosmin- and microcystin-degrading bacteria into Lake Burragorang water resulted in efficient biodegradation of the respective metabolites. For example, microcystin-degrading isolate TT25 was able to degrade three microcystin variants to concentrations below analytical detection within 24 h, suggesting that inoculation of such bacteria has the potential to enhance biodegradation in Lake Burragorang.     

Exploring next generation of IOT devices compatible few mode assisting ring core elliptical cladding optical fiber

Wireless Networks - In this paper, the design method of few mode elliptical ring core fiber (E-RCF) supporting up to 10 spatial linearly polarized (LP) modes is proposed. With the support of...     

Performance analysis of mode division multiplexing based free space optics system incorporating on–off keying and polarization shift keying under dynamic environmental conditions

In this paper, we propose a novel mode division multiplexing (MDM) based FSO transmission system incorporating polarization shift keying (PolSK) to enhance the information carrying capacity of the system. Using numerical simulations, we report the transmission of two independent 40 Gbps information signals using distinct Laguerre Gaussian modes up to an FSO transmission reach of 90 km under the influence of clear environmental conditions using the proposed system. Further, the influence of different environmental conditions such as rain, haze, and fog on the performance of the proposed link using bit error rate as performance metrics has also been investigated in this paper. Also, we report a comparative analysis of PolSK and on–off keying modulation formats in the proposed MDM-FSO link under the same environmental conditions. The simulation results show that under different weather conditions, PolSK based MDM-FSO transmission system demonstrates better performance.