Treatment of Synthetic Olefin Plant Wastewater at Various Salt Concentrations in a Membrane Bioreactor

The objective of this study was to investigate the effect of salt concentration on performance of a membrane bioreactor (MBR) for treating an olefin plant wastewater. For this purpose, a lab‐scale submerged MBR with a flat‐sheet ultrafiltration membrane was used for treatment of synthetic wastewater according to oxidation and neutralization unit of olefin plant. The synthetic wastewater was adjusted to have 500 mg/L chemical oxygen demand (COD). Trials on different concentrations of sodium sulfate (Na₂SO₄) (0–20 000 ppm) in the feed were conducted under aerobic conditions in the MBR. The results showed that increasing the salt concentrations causes an increase in the effluent COD, phenol, and oil concentrations. These results are due to reduction of the membrane filtration efficiency and also decline in the microbial activity that it is indicated by decreasing the sOUR in MBR. But in all the trials, the effluent COD and oil concentration was well within the local discharge limit of 100 and 10 mg/L, respectively. These results indicate that the MBR system is highly efficient for treating the olefin plant wastewater, and although high salt concentrations decreased organic contaminant removal rates in the MBR, the effluent still met the discharge limits for treating the olefin plant wastewater.     

Recovery of Plant Nutrients from Dilute Solutions of Human Urine and Preliminary Investigations on Pot Trials

Within the context of Ecological Sanitation (ECOSAN), human urine has been the subject of research and practice as a potential fertilizer in the recent years. Although quite a lot had been done with original undiluted urine with promising outcomes, not much appears in the literature which concentrates on dilute solutions of urine. This is important because unless waterless toilets are employed, urine will be diluted with flush water in actual use. In this work, dilute solutions of urine are investigated with emphasis on the recovery of plant nutrients. A natural zeolite namely clinoptilolite was loaded with nitrogen, phosphorus, and potassium as an indirect route of processing urine. The results have revealed that hydrolysis is completed in shorter times in dilute samples. Clinoptilolite could successfully remove plant nutrients from all dilute solutions. Nitrogen could be recovered up to 86% with higher efficiencies at higher concentrations in general. Recovery of orthophosphates increases with increasing concentration to reach 96%, however, potassium could not be recovered. The preliminary experiments with grass have revealed that nutrient loaded clinoptilolite was as effective as chemical fertilizers while direct application of original and diluted solutions of urine had shown inferior yields.     

腾格里沙漠典型植物含水率与地物光谱的关系分析

地物光谱特征不仅是遥感机理研究的重要内容,亦是遥感应用分析的重要依据。用ASD手持式光谱仪测定了腾格里沙漠10种典型植物的冠层光谱,对测得光谱数据进行包络线去除和一阶微分处理,并在实验室采用烘干法得到植物的含水率,运用相关系数法分析植物含水率与经包络线去除的光谱数据之间的关系,同时分析了不同含水率植物的红边特征。结果表明：研究区植物最大含水率为88.19%,最小含水率为37.34%;含水率与包络线去除的光谱数据在可见光（561~718 nm）和近红外（861 nm,894 nm）波段均存在极显著相关性,并建立了两者之间的回归模型,说明可见光近红外波段可以反映沙漠植物的水分状况;不同含水率植物的红边参数有所差异。     

Effects of temperature, algae biomass and ambient nutrient on the absorption of dissolved nitrogen and phosphate by Rhodophyte Gracilaria asiatica

Gracilaria asiatica,being highly efficient in nutrient absorption,is cultivated in sea cucumber ponds to remove nutrients such as nitrogen and phosphate.It was cultured in a laboratory simulating field conditions,and its nutrient absorption was measured to evaluate effects of environmental conditions.Ammonia nitrogen(AN),nitrate nitrogen(NN),total inorganic nitrogen(TIN),and soluble reactive phosphorus(SRP) uptake rate and removal efficiency were determined in a 4×2 factorial design experiment in water temperatures(T) at 15℃ and 25℃,algae biomass(AB) at 0.5 g/L and 1.0 g/L,total inorganic nitrogen(TIN) at 30 μmol/L and 60 μmol/L,and soluble reactive phosphorus(SRP) at 3 and 6 μmol/L.AB and ambient TIN or SRP levels significantly affected uptake rate and removal efficiency of AN,NN,TIN,and SRP(P<0.001).G.asiatica in AB of 0.5 g/L showed higher uptake rate and lower removal efficiency relative to that with AB of 1.0 g/L.Nitrogen and phosphorus uptake rate rose with increasing ambient nutrient concentrations;nutrient removal efficiency decreased at higher environmental nutrient concentrations.The algae preferred to absorb AN to NN.Uptake rates of AN,NN,and SRP were significantly affected by temperature(P<0.001);uptake rate was higher for the 25℃ group than for the 15℃ group at the initial experiment stage.Only the removal efficiency of AN and SRP showed a significant difference between the two temperature groups(P<0.01).The four factors had significant interactive effects on absorption of N and P,implying that G.asiatica has great bioremedial potential in sea cucumber culture ponds.     

Replacement of culvert styles has minimal impact on benthic macroinvertebrates in forested,mountainous streams of Northern California

Culvert styles are being replaced on many road-stream crossings to provide long-term (>2 years) benefits, but these projects may result in short-term (0–2 years) biological impacts. We quantified the short-term effects of replacing steel-pipe culverts with open-arch structures on the benthic-macroinvertebrate communities of 6 streams in the Klamath National Forest of Northern California USA. Physical habitat showed notable site-specific effects in channel form and sedimentation, but no significant change among sites. In contrast, we observed small though significant impacts of the culvert style replacement on benthic macroinvertebrates among sites, including a statistically significant reduction in both taxa richness (p = 0.012) and abundance of intolerant taxa (p = 0.004). Moreover, there was also modest evidence of slightly elevated variability in the benthic-macroinvertebrate communities downstream following the replacement of culvert style. The long-term benefits of culvert style replacement that have been observed in other studies may outweigh the minor, short-term biological impacts observed in these streams.     

气举反循环清理地下连续墙槽底沉渣数值分析

为了深入研究用气举反循环清除地下连续墙槽底沉渣的效果,采用Fluent软件,运用模拟数值分析的方法,建立二维模型,并以气举混合器安置深度、空压机清槽压力、沉渣直径为研究对象,得出了如下结论：气举反循环技术能够有效地将沉渣从连续墙基坑底部返出,沉渣的出口速度范围在0.014～1.098 m/s,粘粒的逃逸速度比其它粒径的逃逸速度大;沉渣厚度越大,沉渣清理出来越难。