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A pilot study was carried out to explore the application of carbon dioxide for pH depression in a bubble column and its ability to
inhibit bromate formation for water with a low alkalinity. Results showed that in the absence of ammonia, CO2 was capable of reducing
bromate 38.0%–65.4% with one-unit pH depression. CO2 caused a slightly lower bromate reduction (4.2%) than did H2SO4 when the
pH was depressed to 7.4, and a more a pronounced lower reduction (8.8%) when the pH was depressed to 6.9. In the presence of 0.20
mg/L-N ammonia, bromate was largely inhibited with 73.9% reduction. When the pH was depressed to 7.4, CO2 and H2SO4 showed an
11.3% and 23.5% bromate reduction respectively, demonstrating that the joint use of CO2 and ammonia might be a plausible strategy of
blocking all three bromate formation pathways. CO2 could be applied through the aeration diffuser together with ozone gas, resulting
in a similar bromate reduction compared with the premixing method through Venturi mixer. 相似文献
714.
近海富营养化的结果与对策 总被引:18,自引:0,他引:18
本文综述了国内外有关近海海水富营养经的结果及对策方面的研究成果,对引起近海海水富营养化和外在因素进行了分析与总结。对其可能造成的正面及负面结果进行了逐个剖析,并在此基础上提出了防止健康水体发生富营养化的措施及对已经发生富营养化的水体应采取的切实可行的政策上和和科学上的(物理的、化学的和生物的)对策。 相似文献
715.
Removing nitrogen from wastewater with low chemical oxygen demand/total nitrogen (COD/TN) ratio is a difficult task due to the insufficient carbon source available for denitrification. Therefore, in the present work, a novel sequencing batch biofilm reactor (NSBBR) was developed to enhance the nitrogen removal from wastewater with low COD/TN ratio. The NSBBR was divided into two units separated by a vertical clapboard. Alternate feeding and aeration was performed in the two units, which created an anoxic unit with rich substrate content and an aeration unit deficient in substrate simultaneously. Therefore, the utilization of the influent carbon source for denitrification was increased, leading to higher TN removal compared to conventional SBBR (CSBBR) operation. The results show that the CSBBR removed up to 76.8%, 44.5% and 10.4% of TN, respectively, at three tested COD/TN ratios (9.0, 4.8 and 2.5). In contrast, the TN removal of the NSBBR could reach 81.9%, 60.5% and 26.6%, respectively, at the corresponding COD/TN ratios. Therefore, better TN removal performance could be achieved in the NSBBR, especially at low COD/TN ratios (4.8 and 2.5). Furthermore, it is easy to upgrade a CSBBR into an NSBBR in practice. 相似文献
716.
A preliminary investigation on the occurrence and distribution of antibiotic resistance genes in the Beijiang River, South China 总被引:6,自引:0,他引:6
The occurrence of antibiotic resistance genes (ARGs) was investigated and quantified in 20 water samples collected in the Beijiang River, South China. Sulfonamide- and tetracycline-resistant bacteria were present in 17 and 14 of the collected 20 samples. For sulfonamide ARGs, sulI and sulII were frequently observed in the Beijiang River. The levels of sulI were higher than sulII (p < 0.05), with the mean values of (1.41 ± 1.12) × 10-2 and (1.58 ± 1.71) × 10-3 copies/16S rDNA, respectively. For tetracycline ARGs, tetG had the highest frequency, 100%, followed by tetA (85%), tetO (85%), tetC (70%), tetX (60%), tetM (40%) and tetQ (20%), while tetE and tetS were not detected in all the samples from the Beijiang River. On the other hand, tetC had the highest concentration, ranging from 8.30 × 10-2 to 13.20 copies/16S rDNA. The poor correlation between ARGs and antibiotic concentrations revealed that the self-amplification and persistence of ARGs were the reasons that made ARGs exist in the water environment even though the antibiotic selecting pressure was absent. Because so few field measurements have been conducted for investigating the levels of ARGs in rivers in South China, this study provides an important insight on better understanding the occurrence and spread of ARGs in such an ecosystem. 相似文献
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农药生产过程中产生的苯胺废水,COD浓度高、生物毒性强、可生化性差,一般生化方法很难处理。研究了Fenton与PAC联用处理苯胺废水。结果表明,Fenton氧化处理苯胺废水在最佳条件为pH=6、m(H2O2)/m(COD)=1.8、n(H2O2)/n(Fe2+)=8时,COD和色度去除率分别为78.4%和92.3%。Fenton氧化后废水B/C值由0.037提高到0.324。最佳条件下联用PAC,在投加量为320 mg/L时COD与色度去除率分别为83.6%和94.8%,并且处理时间显著缩短,实际应用中可减少水力停留时间和构筑物体积。 相似文献
719.
4.20芦山地震灾区临街自建单开间砌体结构房屋震害特别严重,本文基于现场调查研究该类特殊房屋的建造习惯、震害特征与损伤机理,研究表明:单开间砌体房屋是芦山地震灾区等四川小城镇比较常见的临街建筑模式,其平面狭长,建造随意,结构体系不合理,构造措施不到位,抗震能力弱;芦山地震地震烈度8、9度灾区单开间砌体房屋底层纵墙剪切破坏,普遍出现严重的贯通整片墙体的斜裂缝或X形裂缝。底层前部房间横墙无纵向支撑,独立墙段过长,横墙压弯破坏出现贯通整片墙体的水平裂缝,并且墙体外鼓;结构刚度中心与质量中心严重偏离,房屋扭转震动加剧墙体裂缝开展,相邻建筑反复碰撞作用是上部楼层震害的主要原因;鞭梢效应加重突变楼层结构损伤,引起出屋面附属建筑严重破坏甚至倒塌,横墙端部剪切断裂乃至溃散。据此,提出了既有单开间砌体房屋加固工作的建议。 相似文献
720.