Rice straw as a source of energy could substitute for fossil fuels and reduce greenhouse gas (GHG) emissions. Thus, the aim of this paper was to analyze the energy and GHG emissions of rice straw to the energy chain in Egypt. The analysis was performed starting from paddy production, straw collection and transportation, and energy generation for two scenarios: power plant and anaerobic digestion plant. The results showed that the paddy production and transportation stage represented the highest contribution of the total energy consumption and GHG emissions for the two scenarios, respectively. The energy potential was estimated with 4193 GWh electricity and 25,647 × 106 MJ of biogas energy. It was also found that use of rice straw as an energy source could reduce the use of fossil fuel and mitigate air pollution from direct burning of rice straw by 3 Mt CO2-eq of GHG emissions.
The current study presents a detailed evaluation and comparison between two integrated anaerobic–aerobic systems for biological wastewater treatment under equal conditions in all aspects (wastewater characteristics, climatic conditions, reactor sizing, and even the measurement methods). The two examined systems are (i) a hybrid upflow anaerobic sludge blanket (hybrid UASB) coupled with integrated fixed-film activated sludge (IFAS) and (ii) a conventional UASB coupled with activated sludge (AS). The present comparative study aims to evaluate and assess the effect of adding carrier-filling media on the performance of the classical integrated UASB-AS. The two parallel pilot-scale systems, hybrid UASB-IFAS and UASB-AS, were installed and operated at a wastewater treatment plant. Three sets of experiments were conducted to examine the influence of the hydraulic retention time (HRT) on the consequent organic and hydraulic loads, temperature, and recirculation rate of the proposed systems. The main results showed that the two investigated systems had a comparably high efficiency for the removal of organic matters and ammonia. Moreover, a paired sample t-test indicated there was a statistically significant effect of the filling media, and the performance of the hybrid UASB-IFAS increased significantly compared with that of the UASB-AS system. An additional benefit of the filling media on the hybrid system was its high stability when changing the organic and hydraulic loads. The optimum HRT was 6 h, with a total chemical oxygen demand (TCOD) percentage removal of approximately 95% in both examined systems. Treatment of sewage under high and low temperatures indicated that increasing the temperature improved the efficiency of the overall process for both systems significantly.
Hexavalent chromium Cr (VI) is a toxic material used in many industries such as tanneries and electroplating industries. Most of the previous researches studied the removal of chromium at lower concentrations up to 600 mg/L but did not tackle the behavior at higher concentrations, which resemble the real concentration of studied tanneries effluents. The present research is a comparative study of different agricultural low cost adsorbents in the removal of high Chromium concentration from industrial wastewater up to 1000 mg/L, compared to a commercial activated carbon. The tested adsorbents are (Banana Waste (BW), Sawdust (SD), Phragmites Australis (PA), Sugarcane Bagasse (SCB), Pea pod peels (PPP) and Rice straw (RS)). The materials were chemically pretreated with acid-alkali except BW was treated with acid only, to improve adsorbent metal binding capacity. Batch experiments were conducted to study the effect of pH, adsorbent dosage, contact time, initial Chromium concentration and temperature on the removal efficiency of Chromium from wastewater. The experiments were conducted in two sets, one for lower concentration (25-50-100-200-400) mg/L and the other for higher concentration (600-800-1000) to simulate the concentration of Chromium in tannery industry effluents. At 1000 mg/L initial concentration, BW achieved the optimum removal efficiency of 73.28% at pH = 3, adsorbent dosage = 25 g/L and contact time of 3 hours with the adsorption capacity was 39 mg/g. For SD at pH=2, 3 hours contact time, 10 g/L dosage, and 30oC the removal ratio was 64.83% and the adsorption capacity was 86.30 mg/g. The equilibrium data for various agricultural adsorbents was being tested with various adsorption isotherm models such as Langmuir, Freundlich and Tempkin. At low concentrations, AC, BW, PA and SCB follows Freundlich isotherm model while SD follows Langmuir isotherm model. At higher concentrations, BW, SD, PA follows Langmuir isotherm while SCB follows Tempkin isotherm model. To evaluate the mechanism of Cr adsorption on different adsorbents, Pseudo-first-order and Pseudo-second-order equations were used. The adsorption process follows Pseudo-second-order for all adsorbents, which confirms the chemisorption of Cr (VI) on different adsorbents.
Vertical-flow constructed wetlands (VFCWs) are an innovative and sustainable nature-based technology for wastewater treatment in rural areas. This work aimed to evaluate the treatment performance of VFCWs using real wastewater, which can provide more accurate and reliable results compared with field-based experiments, and to investigate the use of Paulownia trees in VFCWs for wastewater treatment. To compare the efficiency of the plants based on the treatment performance of the VFCWs, three units were prepared and composed of Paulownia, the commonly used Phragmites Australis, and an unplanted unit used as a control during the experimental program. The results show significant reductions in both the chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) levels for both planted units, with removal ratios for COD and BOD5 of 60% to 98%, respectively. Both Paulownia and Phragmites Australis significantly reduced the levels of COD and BOD5 in the effluent, with removal percentages ranging from 57.1% to 98% for COD and 49.1% to 98% for BOD5. The control unit, without plantings, showed a lower but still significant removal percentage for both COD (from 55.1% to 96.1%) and BOD5 (from 48.3% to 97.8%). Thus, the results reveal that the efficiency of constructed wetlands can be significantly enhanced by the presence of suitable plant species, such as Paulownia and Phragmites Australis, and constructed wetlands can be a viable and cost-effective option for the treatment of wastewater in various settings, with the added benefit of using the relevant biodiversity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.