Evaluation and validation of passive aeration simultaneous nitrification and denitrification (PASND) in a biofilm reactor for Low-Energy wastewater treatment

In today’s rapidly urbanized and industrialized society, there is an increasing need for cost-effective and environmentally sustainable technologies for the removal of nutrients from the polluted water. Wastewater treatment principally relies on microorganisms for their ability to take up organic substrate and nutrients (i.e., nitrogen) from wastewater. The need for active aeration of the bulk wastewater to provide oxidation power to micro-organisms makes the wastewater treatment process extremely energy intensive. However, a recent study suggests that by exposing the biomass directly to air (passive aeration), the cost associated with aeration could be reduced. This thesis aimed to establish such a pas-sively aerated biofilm (to remove organics and nitrogen from wastewater) from activated sludge in order to investigate its real-world feasibility. To enable cost-effective removal of organic compounds, a biofilm enriched with glyco-gen accumulating organism (GAO) was developed by selective enrichment from acti-vated sludge using sequences of anaerobic flooding followed by aerobic exposure of the biofilm directly to the atmosphere. The transition of activated sludge to the GAO biofilm was completed within eight weeks of continuous selective operation. The GAO biofilm enabled anaerobic removal of organic carbon (biochemical oxygen demand or BOD) from wastewater which was stored intracellularly as poly-hydroxyalkanoate (PHA). The PHA was oxidized in the subsequent aerobic stage to regenerate the biofilm’s BOD stor-age capacity. With using acetate as synthetic BOD, the biofilm demonstrated efficient (>99%) and stable removal of organic carbon at an average rate of 256 mg BOD L-1 h-1. Long-term operation of the established GAO biofilm leads to the very low amount of excess sludge produced. This is of particular interest since sludge disposal cost is the second greatest operational expense in traditional wastewater treatment facilities. The av-erage excess sludge (volatile suspended solids or VSS) production rate was found to be 0.05 g VSS g-1 BOD removed which is about 10-times lower than that of activated sludge process. Factors such as the high biomass content (21.41 g VSS L-1 of reactor) and the low growth yield of GAO were found to be associated with little sludge production. In addition, a high number of a predatory protozoan (Tetramitus) was found inhabiting the biofilm that minimized sludge production by effectively grazing on cells. In order to allow next to organic carbon also nitrogen removal from wastewater, a hybrid biofilm system was developed by incorporating zeolite (an ion-exchange material) into the GAO biofilm and activated sludge as the sole source of nitrifying bacteria. During the anaerobic phase, zeolite adsorbed ammonium which was removed in the subsequent aer-obic stage by the combined action of nitrifying and GAO bacteria via simultaneous nitri-fication and denitrification (SND). The occurrence of SND under full atmospheric partial pressure was confirmed by trickling nitrate solution over the biofilm system which resulted in nitrate reduction in full atmospheric condition. Over four months of continu-ous operation, the biofilm reactor demonstrated sustained BOD (>90%) and nitrogen (about 70%) removal performance with a short hydraulic retention time (HRT) of 5 h (2 h anaerobic and 3 h aerobic phase). The inadequate nitrogen removal efficiency was attributed to the limited capacity (1.474 mg NH4+-N g-1) of the zeolite used in this study. However, a subsequent repeat treatment of the effluent in the same biofilm reactor re-sulted in about 96 % ammonium removal from wastewater. The capability of the GAO biofilm to treat high-strength (up to 4-times) wastewater was evaluated while keeping the same anaerobic duration (2 h). The amount of ammonium adsorbed onto zeolite was found to increase proportionally with influent feed concentration. However, the aerobic time required for zeolite regeneration was longer. Compared to single (1x) and double (2x) strength wastewater, the quadruple (4x) strength synthetic wastewater resulted in nitrite accumulation which took about 5 h (aerobic phase) for complete reduction. Similarly, the BOD removal rate of the biofilm system increased from 543 to 2308 mg L-1 h-1 for 1x and 4x strength wastewater, respectively. The in-creased uptake of BOD by GAO biofilm resulted in the improved storage of PHA (5.02 and 18.6 mmol L-1 for 1x and 4x wastewater, respectively) which contributed to the effi-cient regeneration of zeolite. The biofilm system showed its stability for the treatment of different strength wastewater over a period of 2-months operation suggesting the feasi-bility of 4x or more concentrated wastewater treatment using the proposed biofilm tech-nology with low aeration energy input. To further optimize nitrogen removal performance in the zeolite amended GAO biofilm, several anaerobic and aerobic phases were used while keeping the total treatment time the same (8 h). An increase in the treatment cycles from 2 to 8, increased the nitrogen removal efficiency from 79% to >99%. A simple numerical model was developed that could effectively explain the trends of nitrogen removal in multiple treatment cycles on the basis of the Langmuir ion-exchange isotherm. The main conclusion drawn from the study is that passively aerated GAO biofilm system can be established from standard activated sludge within a reasonable time. The amend-ment of the GAO biofilm by the addition of zeolite as an ammonium adsorbent enables nitrogen removal from wastewater. The proposed biofilm technology has the potential to reduce the energy cost associated with aeration while significantly improving nitrogen removal from high-strength wastewater

Does Energy Consumption, Economic Growth, and Foreign Direct Investment Contribute to CO2 Emission? Evidence from Bangladesh

This work used the Johansen Cointegration Test and the Vector Error Correction Model (VECM) cointegration methodology to assess the long-run cointegrating relationship and short-run dynamics in Bangladesh between energy consumption economic growth, foreign direct investment, urbanization, population growth, and carbon emissions. To assess the long-term association between these variables, we examined data from 1972 to 2014, and empirical estimation revealed that all factors are significant at the 1% level of significance in the case of Bangladesh. Thus, energy consumption, economic growth, foreign direct investment, urbanization, population growth, and carbon emissions  all have shown the predicted sign and are statistically significant, indicating that increased energy consumption, gross domestic product, and population increase all are responsible for increased carbon emissions in Bangladesh. Higher FDI inflows, on the other hand, cut per capita carbon emissions in Bangladesh. On the other hand, the empirical outcome has revealed that there is no substantial causal association between carbon emissions and urbanization. Keywords: CO2; FDI; GDP; population growth; energy consumption; VECM DOI: 10.7176/JESD/12-12-05 Publication date:June 30th 202

Sonochemical Synthesis, Characterization, and Photocatalytic Performance Evaluation of Au/ZnO Nanocomposite for Methyl Orange Degradation

This study examines the impact of gold (Au) incorporation on zinc oxide (ZnO) nanoparticles. Both pure ZnO and Au/ZnO nanocomposite have been synthesized using a unique and environmentally friendly sonochemical approach. The as-synthesized Au/ZnO nanocomposite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) spectroscopic techniques. Under UV-visible irradiation, the photocatalytic effectiveness of ZnO nanoparticles and Au/ZnO nanocomposites for the degradation of dye was examined. The results demonstrated that the nanocomposite has greater photocatalytic activity than ZnO nanoparticles. This is due to the effective electron transfer from ZnO to Au prolonging the lifetime of photogenerated holes, which play the most important role in the dye degradation process.&nbsp

INDUCED SPAWNING AND LARVAL DEVELOPMENT OF VIETNAMESE KOI, Anabas testudineus (Bloch, 1792), USING SALMON GONADOTROPIN RELEASING HORMONE ANALOGUE (S-GnRHA)

The present research work has been carried out to obtain evidence on breeding and embryonic growth of A. testudineus by using S-GnRHa. Fish were injected with three different doses (0.25, 0.5, and 1.0 mL/kg body weight) of synthetic hormone S-GnRHa each with three replications, where male brood fish received half of the doses of female. The fecundity of A. testudineus was ranged from 47,227 to 77,561 during the study period and except control group all the hormone received group ovulated within 12 hours of hormone injection. Among all groups, the highest fertilization rate (89.33%), highest hatching rate (79.5%) as well as highest survival rate (67.0%) was obtained at 0.5 mL/kg body weight hormone dose recipient group. The fertilized egg’s diameter was recorded as 77.59 ± 3.50 µm. The first cleavage had appeared within 18-25 min of fertilization and eventually the morula, blastula, and gastrula stages were observed at 3:10 h, 4 h, and 5:30 h, respectively after fertilization. Larvae with distinguished head, body form and tail appendage spotted between 17-22 h and the larvae started hatching at 19 h after fertilization. The average length of larvae accounted as 105.41 ± 3.73 µm. The findings of present study revealed that 0.5 mL/kg S-GnRHa could be efficient dose for successful induced breeding of A. testudineus

Multi-Perspective, Simultaneous Embedding

We describe MPSE: a Multi-Perspective Simultaneous Embedding method for visualizing high-dimensional data, based on multiple pairwise distances between the data points. Specifically, MPSE computes positions for the points in 3D and provides different views into the data by means of 2D projections (planes) that preserve each of the given distance matrices. We consider two versions of the problem: fixed projections and variable projections. MPSE with fixed projections takes as input a set of pairwise distance matrices defined on the data points, along with the same number of projections and embeds the points in 3D so that the pairwise distances are preserved in the given projections. MPSE with variable projections takes as input a set of pairwise distance matrices and embeds the points in 3D while also computing the appropriate projections that preserve the pairwise distances. The proposed approach can be useful in multiple scenarios: from creating simultaneous embedding of multiple graphs on the same set of vertices, to reconstructing a 3D object from multiple 2D snapshots, to analyzing data from multiple points of view. We provide a functional prototype of MPSE that is based on an adaptive and stochastic generalization of multi-dimensional scaling to multiple distances and multiple variable projections. We provide an extensive quantitative evaluation with datasets of different sizes and using different number of projections, as well as several examples that illustrate the quality of the resulting solutions

128-QAM Based mm-Wave Communication (5G) Architecture

Demand for bandwidth can never be fulfilled with any definite amount. Population is growing at a high speed which also causes an increase in the demand for bandwidth. Currently available bands ranging up-to 10 GHz is at the edge of saturation. So a newer and unutilized bandwidth is mandatory for the fulfillment of the increasing bandwidth demand. The millimeter wave band which is fully used. This band offers a wide range of bandwidth (30 GHz ~ 300 GHz). A slight part of this band, the E-band, has been used in the design of the 5G network proposed in this paper. Single-carrier frequency-division multiple access (SC-FDMA) and orthogonal frequency-division multiple access (OFDMA) have been proposed for the uplink and downlink multiple access respectively. A Rayleigh fading channel is used as the propagation environment along with considering different losses at sea level (T = 0 ˚C, P = 760 mm Hg, H2O = 1 gm/m3). 128-quadrature amplitude modulation (QAM) has been used as the principle modulation technique. Also, the use of adaptive beam-forming antennas ensure an increased coverage of about 2 km