Increases in the treatment of water to meet the growing water demand ultimately result in unmanageable quantities of residuals,the handling,and disposal of which is a major environmental issue.Consequently,research in...Increases in the treatment of water to meet the growing water demand ultimately result in unmanageable quantities of residuals,the handling,and disposal of which is a major environmental issue.Consequently,research into beneficial reuse of water treatment residuals continues unabated.This study investigated the applicability of lime-iron sludge for phosphate adsorption by fixed-bed column adsorption.Laboratory-scale experiments were conducted at varying flow rates and bed depths.Fundamental and empirical models(Thomas,Yan,Bohart-Adams,Yoon-Nelson,and Wolboroska)as well as artificial intelligence techniques(Artificial neural network(ANN)and Adaptive neuro-fuzzy inference system(ANFIS))were used to simulate experimental breakthrough curves and predict column dynamics.Increase in flow rate resulted in reduced adsorption capacity.However,adsorption capacity was not affected by bed depth.ANN was superior in predicting breakthrough curves and predicted breakthrough times with high accuracy(R^2>0.9962).Na OH(0.5 mol·L^-1)was successfully used to regenerate the adsorption bed.After nine cyclic adsorption/desorption runs,only a marginal decrease in adsorption and desorption efficiencies of 10%and 8%respectively was observed.The same regenerate Na OH solution was reused for all desorption cycles.After nine cycles the eluent desorbed a total of 1550 mg phosphate exhibiting potential for further reuse.展开更多
Expansive soils present a significant geohazard to light infrastructure world-wide,causing costly damage through swelling and shrinkage cycles driven by moisture content changes.One key property controlling this behav...Expansive soils present a significant geohazard to light infrastructure world-wide,causing costly damage through swelling and shrinkage cycles driven by moisture content changes.One key property controlling this behavior,the Cation Exchange Capacity(CEC),is complex and expensive to measure directly,making it necessary to find reliable and affordable proxies for initial site assessments.This study introduces and validates a novel parameter,the weighted plasticity index(wPI),for classifying the swelling potential of expansive clays.Twenty-six soil samples,representing a range from low to high plasticity clays from Trinidad,underwent standard geotechnical laboratory tests,including Atterberg limits and grain size analysis.The wPI was calculated for each sample as the product of its Plasticity Index(PI)and the percentage of fine particles(percent passing the 425-μm sieve).A strong linear relationship(R^(2)=0.94)was found between the wPI and the Liquid Limit(LL).Using a previously established relationship between LL and CEC,a robust mathematical model connecting wPI directly to CEC was derived.This model formed the basis for a new four-tiered swelling potential classification system(Low,Medium,High,and Very High)based on the calculated wPI values.The wPI method provides a reliable,quick,and cost-effective tool for geotechnical engineers to evaluate swelling potential,promoting the design of more resilient and sustainable infrastructure in areas prone to expansive soils.展开更多
文摘Increases in the treatment of water to meet the growing water demand ultimately result in unmanageable quantities of residuals,the handling,and disposal of which is a major environmental issue.Consequently,research into beneficial reuse of water treatment residuals continues unabated.This study investigated the applicability of lime-iron sludge for phosphate adsorption by fixed-bed column adsorption.Laboratory-scale experiments were conducted at varying flow rates and bed depths.Fundamental and empirical models(Thomas,Yan,Bohart-Adams,Yoon-Nelson,and Wolboroska)as well as artificial intelligence techniques(Artificial neural network(ANN)and Adaptive neuro-fuzzy inference system(ANFIS))were used to simulate experimental breakthrough curves and predict column dynamics.Increase in flow rate resulted in reduced adsorption capacity.However,adsorption capacity was not affected by bed depth.ANN was superior in predicting breakthrough curves and predicted breakthrough times with high accuracy(R^2>0.9962).Na OH(0.5 mol·L^-1)was successfully used to regenerate the adsorption bed.After nine cyclic adsorption/desorption runs,only a marginal decrease in adsorption and desorption efficiencies of 10%and 8%respectively was observed.The same regenerate Na OH solution was reused for all desorption cycles.After nine cycles the eluent desorbed a total of 1550 mg phosphate exhibiting potential for further reuse.
文摘Expansive soils present a significant geohazard to light infrastructure world-wide,causing costly damage through swelling and shrinkage cycles driven by moisture content changes.One key property controlling this behavior,the Cation Exchange Capacity(CEC),is complex and expensive to measure directly,making it necessary to find reliable and affordable proxies for initial site assessments.This study introduces and validates a novel parameter,the weighted plasticity index(wPI),for classifying the swelling potential of expansive clays.Twenty-six soil samples,representing a range from low to high plasticity clays from Trinidad,underwent standard geotechnical laboratory tests,including Atterberg limits and grain size analysis.The wPI was calculated for each sample as the product of its Plasticity Index(PI)and the percentage of fine particles(percent passing the 425-μm sieve).A strong linear relationship(R^(2)=0.94)was found between the wPI and the Liquid Limit(LL).Using a previously established relationship between LL and CEC,a robust mathematical model connecting wPI directly to CEC was derived.This model formed the basis for a new four-tiered swelling potential classification system(Low,Medium,High,and Very High)based on the calculated wPI values.The wPI method provides a reliable,quick,and cost-effective tool for geotechnical engineers to evaluate swelling potential,promoting the design of more resilient and sustainable infrastructure in areas prone to expansive soils.
