Decentralized wastewater containing elevated salinity is an emerging threat to the local environment and sanitation in remote coastal communities.Regarding the cost and treatment efficiencies,we propose a passive aera...Decentralized wastewater containing elevated salinity is an emerging threat to the local environment and sanitation in remote coastal communities.Regarding the cost and treatment efficiencies,we propose a passive aeration ditch(PAD)using non-woven polyester fabric as a feasible bubbleless aerator and biofilm carrier for wastewater treatment.Consideration has been first given to PAD’s efficacy in treating saline decentralized wastewater,and then to the impact of chemical oxygen demand-to-nitrogen(C/N)ratio and salinity on biofilm formation.A multispecies model incorporating the salinity effect has been developed to depict the system performance and predict the microbial community.Results showed that the PAD system had great capacity for pollutants removal.The biofilm thickness increased at a higher C/N ratio because of the boost of aerobic heterotrophs and denitrifying bacteria,which consequently improved the COD and total nitrogen removal.However,this led to the deterioration of ammonia removal.Moreover,while a higher salinity benefited the biofilm growth,the contaminant removal efficiencies decreased because the salinity inhibited the activity of aerobic heterotrophs and reduced the abundance of nitrifying bacteria inside the biofilm.Based on the model simulation,feed water with salinity below 2%and C/N ratio in a range of 1 to 3 forms a biofilm that can reach relatively high organic matter and ammonia removal.These findings not only show the feasibility of PAD in treatment of saline decentralized wastewater,but also offer a systematic strategy to predict and optimize the process performance.展开更多
The aim of this study was to uncover ways to mitigate greenhouse gas（GHG） emissions and reduce energy consumption during the composting process. We assessed the effects of different aeration rates（0, 0.18, 0.36, an...The aim of this study was to uncover ways to mitigate greenhouse gas（GHG） emissions and reduce energy consumption during the composting process. We assessed the effects of different aeration rates（0, 0.18, 0.36, and 0.54 L/（kg dry matter（dm）·min）） and methods（continuous and intermittent） on GHG emissions. Pig feces and corn stalks were mixed at a ratio of 7：1. The composting process lasted for 10 weeks, and the compost was turned approximately every 2 weeks. Results showed that both aeration rate and method significantly affected GHG emissions. Higher aeration rates increased NH3 and N2O losses,but reduced CH4 emissions. The exception is that the CH4 emission of the passive aeration treatment was lower than that of the low aeration rate treatment. Without forced aeration,the CH4 diffusion rates in the center of the piles were very low and part of the CH4 was oxidized in the surface layer. Intermittent aeration reduced NH3 and CH4 losses, but significantly increased N2 O production during the maturing periods. Intermittent aeration increased the nitrification/denitrification alternation and thus enhanced the N2 O production. Forced aeration treatments had higher GHG emission rates than the passive aeration treatment. Forced aeration accelerated the maturing process, but could not improve the quality of the end product. Compared with continuous aeration, intermittent aeration could increase the O2 supply efficiency and reduced the total GHG emission by 17.8%, and this reduction increased to 47.4% when composting was ended after 36 days.展开更多
Landfilled organic waste, in the presence of oxygen, can undergo aerobic decomposition facilitated by heterotrophic microorganisms. Aerobic degradation of solid waste can quickly consume available oxygen thus curtaili...Landfilled organic waste, in the presence of oxygen, can undergo aerobic decomposition facilitated by heterotrophic microorganisms. Aerobic degradation of solid waste can quickly consume available oxygen thus curtailing further degradation. The aim of this study was the investigation of a low-cost method of replenishing oxygen consumed in landfilled waste. Three 2D lysimeters were established to investigate the effectiveness of stand-alone, vertical ventilation pipes inserted into waste masses. Two different configurations of ventilation were tested with the third lysimeter acting as an unventilated control. Lysimeters were left uninsulated and observed over the course of 6 months with regular collection of gas and leachate samples. Lysimeters were then simulated for Oxygen (O<sub>2</sub>) and Nitrous oxide (N<sub>2</sub>O) to analyze the denitrification contributions of each. The experiment revealed that a single ventilation pipe can increase the mean oxygen level of a 1.7 m × 1.0 m area by up to 13.5%. It also identified that while increasing the density of ventilation pipes led to increased O<sub>2</sub> levels, this increase was not significant at the 0.05 probability level. A single vent averaged 13.67% O<sub>2</sub> while inclusion of an additional vent in the same area only increased the average to 14.59%, a 6.7% increase. Simulation helped to verify that lower ventilation pipe placement density may be more efficient as in addition to the effect on oxygenation, denitrification efficiency may increase. Simulations of N<sub>2</sub>O production estimated between 8% - 20% more N<sub>2</sub>O being generated with lower venting density configurations.展开更多
The aims of this study are to determine the effect of Sabah ragi on food waste and dry leaves composting as well as to compare the composting performance from a previous study that had no addition of Sabah ragi.The co...The aims of this study are to determine the effect of Sabah ragi on food waste and dry leaves composting as well as to compare the composting performance from a previous study that had no addition of Sabah ragi.The composting process was conducted using an in-vessel passive aerated bioreactor with turning every 3 days for 40 days.Based on the physiochemical analysis,the stability and maturity of the compost were evaluated.Parameters such as temperature,total organic carbon,moisture content,pH,conductivity,and C/N were monitored.During the composting process,the highest temperature of 54.2℃ and the highest heat generation rate per initial mass of compost dry matter of 4098 kJ kg^(-1) day^(-1) was achieved on day 7.Furthermore,when compared to previous studies,this study achieved a faster thermophilic phase(≥45℃),a longer thermophilic period(4 days),and a higher cumulative temperature.Elementary kinetic analysis was performed based on the TOC profile and evaluated using coefficient correlation(R^(2)).In this study,application of the second-order model resulted in good responses.Low pathogen levels and higher nitrogen content were detected in the final compost,while some of the nutrients were not in the recommended range.An estimated ragi cost of RM 1.22 was required for every 1 kg of compost with a selling price of RM 6.00/kg of compost.展开更多
基金supported by Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(China)(No.GML2019ZD0403)the Program for Guangdong Introducing Innovative and Entrepreneurial Teams(China)(No.2019ZT08L213)+1 种基金the China Postdoctoral Science Foundation(No.2020M672540)the joint Fund Project of Guangdong Basic and Applied Basic Research Fund(China)(No.2020A1515110309).
文摘Decentralized wastewater containing elevated salinity is an emerging threat to the local environment and sanitation in remote coastal communities.Regarding the cost and treatment efficiencies,we propose a passive aeration ditch(PAD)using non-woven polyester fabric as a feasible bubbleless aerator and biofilm carrier for wastewater treatment.Consideration has been first given to PAD’s efficacy in treating saline decentralized wastewater,and then to the impact of chemical oxygen demand-to-nitrogen(C/N)ratio and salinity on biofilm formation.A multispecies model incorporating the salinity effect has been developed to depict the system performance and predict the microbial community.Results showed that the PAD system had great capacity for pollutants removal.The biofilm thickness increased at a higher C/N ratio because of the boost of aerobic heterotrophs and denitrifying bacteria,which consequently improved the COD and total nitrogen removal.However,this led to the deterioration of ammonia removal.Moreover,while a higher salinity benefited the biofilm growth,the contaminant removal efficiencies decreased because the salinity inhibited the activity of aerobic heterotrophs and reduced the abundance of nitrifying bacteria inside the biofilm.Based on the model simulation,feed water with salinity below 2%and C/N ratio in a range of 1 to 3 forms a biofilm that can reach relatively high organic matter and ammonia removal.These findings not only show the feasibility of PAD in treatment of saline decentralized wastewater,but also offer a systematic strategy to predict and optimize the process performance.
基金supported by the National Natural Science Foundation of China (No. 41201282)part of the Chinese National Science and Technology Support Program (2012BAD14B01/06/18)Leshan Normal University Foundation Z1159
文摘The aim of this study was to uncover ways to mitigate greenhouse gas（GHG） emissions and reduce energy consumption during the composting process. We assessed the effects of different aeration rates（0, 0.18, 0.36, and 0.54 L/（kg dry matter（dm）·min）） and methods（continuous and intermittent） on GHG emissions. Pig feces and corn stalks were mixed at a ratio of 7：1. The composting process lasted for 10 weeks, and the compost was turned approximately every 2 weeks. Results showed that both aeration rate and method significantly affected GHG emissions. Higher aeration rates increased NH3 and N2O losses,but reduced CH4 emissions. The exception is that the CH4 emission of the passive aeration treatment was lower than that of the low aeration rate treatment. Without forced aeration,the CH4 diffusion rates in the center of the piles were very low and part of the CH4 was oxidized in the surface layer. Intermittent aeration reduced NH3 and CH4 losses, but significantly increased N2 O production during the maturing periods. Intermittent aeration increased the nitrification/denitrification alternation and thus enhanced the N2 O production. Forced aeration treatments had higher GHG emission rates than the passive aeration treatment. Forced aeration accelerated the maturing process, but could not improve the quality of the end product. Compared with continuous aeration, intermittent aeration could increase the O2 supply efficiency and reduced the total GHG emission by 17.8%, and this reduction increased to 47.4% when composting was ended after 36 days.
文摘Landfilled organic waste, in the presence of oxygen, can undergo aerobic decomposition facilitated by heterotrophic microorganisms. Aerobic degradation of solid waste can quickly consume available oxygen thus curtailing further degradation. The aim of this study was the investigation of a low-cost method of replenishing oxygen consumed in landfilled waste. Three 2D lysimeters were established to investigate the effectiveness of stand-alone, vertical ventilation pipes inserted into waste masses. Two different configurations of ventilation were tested with the third lysimeter acting as an unventilated control. Lysimeters were left uninsulated and observed over the course of 6 months with regular collection of gas and leachate samples. Lysimeters were then simulated for Oxygen (O<sub>2</sub>) and Nitrous oxide (N<sub>2</sub>O) to analyze the denitrification contributions of each. The experiment revealed that a single ventilation pipe can increase the mean oxygen level of a 1.7 m × 1.0 m area by up to 13.5%. It also identified that while increasing the density of ventilation pipes led to increased O<sub>2</sub> levels, this increase was not significant at the 0.05 probability level. A single vent averaged 13.67% O<sub>2</sub> while inclusion of an additional vent in the same area only increased the average to 14.59%, a 6.7% increase. Simulation helped to verify that lower ventilation pipe placement density may be more efficient as in addition to the effect on oxygenation, denitrification efficiency may increase. Simulations of N<sub>2</sub>O production estimated between 8% - 20% more N<sub>2</sub>O being generated with lower venting density configurations.
基金The authors acknowledge University Malaysia Sabah for the financial aid(SDG03-2020)Dana Inovasi Sekolah(DIS0005-2020)postdoctoral awarded to Dr.Junidah Lamaming.
文摘The aims of this study are to determine the effect of Sabah ragi on food waste and dry leaves composting as well as to compare the composting performance from a previous study that had no addition of Sabah ragi.The composting process was conducted using an in-vessel passive aerated bioreactor with turning every 3 days for 40 days.Based on the physiochemical analysis,the stability and maturity of the compost were evaluated.Parameters such as temperature,total organic carbon,moisture content,pH,conductivity,and C/N were monitored.During the composting process,the highest temperature of 54.2℃ and the highest heat generation rate per initial mass of compost dry matter of 4098 kJ kg^(-1) day^(-1) was achieved on day 7.Furthermore,when compared to previous studies,this study achieved a faster thermophilic phase(≥45℃),a longer thermophilic period(4 days),and a higher cumulative temperature.Elementary kinetic analysis was performed based on the TOC profile and evaluated using coefficient correlation(R^(2)).In this study,application of the second-order model resulted in good responses.Low pathogen levels and higher nitrogen content were detected in the final compost,while some of the nutrients were not in the recommended range.An estimated ragi cost of RM 1.22 was required for every 1 kg of compost with a selling price of RM 6.00/kg of compost.
