Optimal Policies for Aggregate Recycling from Decommissioned Forest Roads

To mitigate the adverse environmental impact of forest roads, especially degradation of endangered salmonid habitat, many public and private land managers in the western United States are actively decommissioning roads where practical and affordable. Road decommissioning is associated with reduced long-term environmental impact. When decommissioning a road, it may be possible to recover some aggregate (crushed rock) from the road surface. Aggregate is used on many low volume forest roads to reduce wheel stresses transferred to the subgrade, reduce erosion, reduce maintenance costs, and improve driver comfort. Previous studies have demonstrated the potential for aggregate to be recovered and used elsewhere on the road network, at a reduced cost compared to purchasing aggregate from a quarry. This article investigates the potential for aggregate recycling to provide an economic incentive to decommission additional roads by reducing transport distance and aggregate procurement costs for other actively used roads. Decommissioning additional roads may, in turn, result in improved aquatic habitat. We present real-world examples of aggregate recycling and discuss the advantages of doing so. Further, we present mixed integer formulations to determine optimal levels of aggregate recycling under economic and environmental objectives. Tested on an example road network, incorporation of aggregate recycling demonstrates substantial cost-savings relative to a baseline scenario without recycling, increasing the likelihood of road decommissioning and reduced habitat degradation. We find that aggregate recycling can result in up to 24% in cost savings (economic objective) and up to 890% in additional length of roads decommissioned (environmental objective).     

Universally improving effect of mixed electron donors on the CO2 fixing efficiency of nonphotosynthetic microbial communities from marine environments

The universality of improved CO2 fixing upon the addition of mixed electron donors（MEDs）composed of Na2 S,NO2-,and S2O32-to non-photosynthetic microbial communities（NPMCs）obtained from 12 locations in four oceans of the world was validated. The CO2 fixing efficiencies of NPMCs were universally enhanced by MED compared with those obtained using H2 alone as electron donor,with average increase of about 276%. An increase in microbial inoculation concentration could increase the net amount of CO2 fixing to853.34 mg/L in the presence of MED. NO2-and S2O32-may play the roles of both electron acceptor and electron donor under aerobic conditions,which may improve the energy utilization efficiency of NPMC and enhance the CO2 fixation efficiency. The sequence determination of 16 S ribosomal deoxyribonucleic acid（rDNA） from 150 bacteria of NPMC showed that more than 50% of the bacteria were symbiotic and there were many heterotrophic bacteria such as Vibrio natriegens. These results indicate that NPMC acts as a symbiotic CO2 fixing system. The interaction between autotrophic and heterotrophic bacteria may be a crucial factor supporting ladder utilization and recycling of energy/carbon source.     

贵州普定喀斯特关键带土壤重金属形态特征及风险评价

采用BCR分步提取法对普定喀斯特关键带不同土地利用方式下土壤重金属(如Cd、 Cr、 Zn、 Fe、 Ni和Mn)的分布及其形态进行分析,评估了重金属的生物有效性以及生态环境潜在风险.结果表明,土壤重金属Fe、 Zn、 Cr和Ni主要以残渣态的形式存在,不易被生物所利用;而Cd和Mn的有效态含量较高,有较强的迁移性和生物有效性.普定土壤中丰富的有机质有利于重金属Cd、 Fe、 Cr和Ni的可氧化态转化,Ni、 Fe和Mn的可氧化态倾向于富集在土壤大团聚体内.风险评估指数法(RAC)和次生相与原生相分布比值法(RSP)评估结果显示,普定土壤表现出轻微生态危害,土壤中大部分重金属(除Cd)对生态环境有较低的风险,耕地和弃耕地中Cd对环境构成的风险更高,与施肥和喷洒农药等活动造成土壤中外源金属元素输入有关.     

活性污泥耗氧速率的测定及其影响因素试验分析

本文首先介绍了活性污泥净化能力判别指标——耗氧速率的原电池氧测定法,继而通过试验研究了一些相关的影响因素同比耗氧速率的关系,最后分析说明了比耗氧速率在监控活性污泥系统运行中所起的作用。     

Scrap Iron Filings assisted nitrate and phosphate removal in low C/N waters using mixed microbial culture

• Microbes enhance denitrification under varying DO concentrations and SIF dosages. • Abiotic nitrate reduction rates are proportional to SIF age and dosage. • Over 80% of the simultaneously loaded NO₃⁻-N and PO₄³⁻ is removed biologically. This study focuses on identifying the factors under which mixed microbial seeds assist bio-chemical denitrification when Scrap Iron Filings (SIF) are used as electron donors and adsorbents in low C/N ratio waters. Batch studies were conducted in abiotic and biotic reactors containing fresh and aged SIF under different dissolved oxygen concentrations with NO₃⁻-N and/or PO₄^3- influent(s) and their nitrate/phosphate removal and by-product formations were studied. Batch reactors were seeded with a homogenized mixed microbial inoculum procured from natural sludges which were enriched over 6 months under denitrifying conditions in the presence of SIF. Results indicated that when influent containing 40 mg/L of NO₃⁻-N was treated with 5 g SIF, 79.9% nitrate reduction was observed in 8 days abiotically and 100% removal was accomplished in 20 days when the reactor was seeded. Both abiotic and seeded reactors removed more than 92% PO₄³⁻ under high DO conditions in 12 days. Abiotic and biochemical removal of NO₃⁻-N and abiotic removal of PO₄³⁻ were higher under independent NO₃⁻-N/PO₄³⁻ loading, while 99% PO₄^3- was removed biochemically under combined NO₃⁻-N and PO₄³⁻ loading. This study furthers the understandings of nitrate and phosphate removal in Zero Valent Iron (ZVI) assisted mixed microbial systems to encourage the application of SIF-supported bio-chemical processes in the simultaneous removals of these pollutants.     

改良的SBR新工艺在抚顺市三宝屯污水处理厂的应用

通过DAT-IAT工艺应用于抚顺市三宝屯污水处理厂的工艺流程特点,主要处理构筑物的构造形式及设计参数,处理系统的运行效果及处理成本,分析设计与运行中存在的主要问题及应对措施,为SBR新工艺在北方寒冷地区应用提供设计参数和运行管理经验。     

环氧氯丙烷生产废水处理工程实例

针对某集团公司排放的环氧氯丙烷生产废水、造纸废水,采用高温碱破对环氧氯丙烷生产废水预处理后,与等体积的造纸废水（经混凝沉淀－厌氧预处理后的排水）形成混合废水,该混合废水采用“水解酸化+卡鲁塞尔氧化沟”组合工艺进行处理。工程实践表明,该组合工艺能够稳定有效处理混合废水,出水水质能达到当地工业园区污水处理厂的排放标准（ρ（COD）≤500 mg/L）,组合工艺处理成本约为5.47元/t,具有处理效果好、运行成本低等优点。     

Determination of renewable energy yield from mixed waste material from the use of novel image analysis methods

Two novel techniques are presented in this study which together aim to provide a system able to determine the renewable energy potential of mixed waste materials. An image analysis tool was applied to two waste samples prepared using known quantities of source-segregated recyclable materials. The technique was used to determine the composition of the wastes, where through the use of waste component properties the biogenic content of the samples was calculated. The percentage renewable energy determined by image analysis for each sample was accurate to within 5% of the actual values calculated. Microwave-based multiple-point imaging (AutoHarvest) was used to demonstrate the ability of such a technique to determine the moisture content of mixed samples. This proof-of-concept experiment was shown to produce moisture measurement accurate to within 10%. Overall, the image analysis tool was able to determine the renewable energy potential of the mixed samples, and the AutoHarvest should enable the net calorific value calculations through the provision of moisture content measurements. The proposed system is suitable for combustion facilities, and enables the operator to understand the renewable energy potential of the waste prior to combustion.     

Enhanced catalytic complete oxidation of 1,2-dichloroethane over mesoporous transition metal-doped γ-Al_2O_3

High-surface-area mesoprous powders of γ-Al2O3 doped with Cu2+, Cr3+, and V3+ions were prepared via a modified sol–gel method and were investigated as catalysts for the oxidation of chlorinated organic compounds. The composites retained high surface areas and pore volumes comparable with those of undoped γ-Al2O3 and the presence of the transition metal ions enhanced their surface acidic properties. The catalytic activity of the prepared catalysts in the oxidation of 1,2-dichloroethane(DCE) was studied in the temperature range of 250–400°C. The catalytic activity and product selectivity were strongly dependent on the presence and the type of dopant ion. While Cu2+- and Cr3+-containing catalysts showed100% conversion at 300°C and 350°C, V3+-containing catalyst showed considerably lower conversion. Furthermore, while the major products of the reactions over γ-alumina were vinyl chloride(C2H3Cl) and hydrogen chloride(HCl) at all temperatures, Cu- and Cr-doped catalysts showed significantly stronger capability for deep oxidation to CO2.     

国外物质流分析研究进展

回顾了国外物质流分析研究的起源和发展,并对其主流研究方法作一概述;探讨了物质流分析研究框架及指标体系的发展及应用,对30余个国家的指标体系使用情况做一统计;总结了国外已研究物质流分析的主要国家物质流分析信息的应用情况;指出了国外物质流分析研究的不足之处。