High nitrite is a known operation parameter to inhibit the biological oxidation of nitrite to nitrate. The phenomenon is traditionally expressed using a Monod-type equation with non-competitive inhibition, in which the reaction associated with the biomass growth is reduced when high nitrite is present. On the other hand, very high nitrite is also known to slay nitrifiers. To clarify the difference between the growth inhibition and the poisoning, cell counting for living microorganisms in the nitrite oxidiser-enriched activated sludge was conducted in batch conditions under various nitrite concentrations together with measurements of biomass chemical oxygen demand (COD) concentration and oxygen uptake rate. The experiments demonstrated that these measureable parameters were all decayed when nitrite concentration exceeded 100-500 mgN/L at pH 7.0 in the system, indicating that nitrite poisoning took place. Biomass growth was recognised in lower range of nitrite which was expressed with growth inhibition only. Based on the response, a kinetic model for the biological nitrite oxidation was developed with a modification of IWA ASM1. The model was further utilised to calculate a possibility to wash out nitrite oxidiser in the aeration tank where a part of the return activated sludge was exposed to high nitrite liquor in a side-stream partial nitritation reactor.
Purpose This study aims to evaluate the potential negative effects of rice husk as a source of fertilizer on plant growth. Methods Growth tests were conducted on komatsuna (Brassica rapa var. perviridis) using three types of experiment. A pot experiment was conducted to compare different fertilizers on an individual basis. A second pot experiment was conducted to compare different mixtures of fertilizers. Finally, a field experiment was performed to determine the effects of the application of different quantities of silica. Results The results showed that komatsuna grew better with the application of silica mixed with fertilizer, and that there was an optimal quantity of silica to be used, when used on its own. It was found that, in all cases, the silica in the rice husk ash did not have any measurable negative effects on the growth of the komatsuna. Conclusions We, therefore, conclude that rice husk silica can undoubtedly be used for plant cultivation.
In Hanoi, the capital of Vietnam, lakes and rivers are polluted by both point pollution sources such as discharge from sewerage system; and by non-point pollution sources such as washoff from land surface and leakage from septic tanks. Several studies had mentioned about water pollution but were mainly focusing on organic pollution, feacal contamination and pollutant sources from surface runoff were not considered. To investigate the characteristics of pollutant variation in runoff water and feacal contamination by pathogenic indicators, water samples were collected in August and September 2008, by the roadside and at the inflows of lakes under wet weather condition in the downtown of Hanoi. Monitoring results showed high pollutant concentration, especially pathogenic indicators as E.coli and total coliform (TC), both in road runoff and water that flowed into lakes. Runoff water quality was much different depending on the sampling locations and patterns of rainfall. Pollutant concentration collected by the roadside tend to increase at the end of rainfall. It might be attributed to the discharge of domestic wastewater from individual households or leakage from septic systems. Time and spatial variation were much different for each event that made urban runoff water to be more difficult to control in comparison with domestic wastewater. Cluster analysis was applied to find the similarities of water quality among sampling locations. It was a useful method to find the spatial variation of pollutants and their level of pollution.
Allylthiourea is a known specific inhibitor for ammonium oxidiser to suppress its oxygen uptake, and is commonly used for various kinds of batch respirometric tests to detect heterotrophic respiration in activated sludge. However, when high heterotrophs were present in the sample, it appeared the inhibitor was noticeably degraded and reached below the inhibition threshold after a couple of days, which resulted in overestimation of the heterotrophic respiration. The biological decomposition of the inhibitor was expressed with a Monod-type rate expression having a half-saturation coefficient of 980 mg-COD/L and maximum specific growth rate of 1.0 d. The developed kinetic model, including the growth and decay of the heterotrophs and nitrifiers, indicated that the ATU with about 90 mg-ATU/L which was initially dosed to the system would reach below the inhibition threshold of 1.0 mg-ATU/L after 10 days when 750 mg-COD/L of heterotrophs were present. From the kinetic model, an empirical formula to calculate a safe minimum ATU dose for the batch respirometric test was elaborated. The model also provided a modified experimental procedure to accurately estimate the initial heterotrophic biomass concentration in the sample and its specific decay rate based on IWA Activated Sludge Models.
Extremely lightweight of rice husks due to low specific gravity is disadvantageous for accelerating its usage. To overcome this disadvantage, rice husks are sometimes compacted, that is, pelletized or solidified to assist easy and cheap collection and hauling. However, the compaction process may negatively affect the properties of silica in the husk. In this study, the influence of the compaction process was studied through the solubility and physical properties of silica. Two types of fuels, pellet and stick fuels, were synthesized and their influence on the properties of the fuel ash was evaluated. Consequently, stick fuels were better than pellet fuels in terms of fertilizer use of the ash during their use in residential stoves and small commercial heaters. Contrastingly, rice husks in the existing form were better than stick fuels under washing conditions; however, rice husks had disadvantages in terms of cost and handling during collection and hauling. Selection of rice husks in their existing form or compacted rice husks must be carefully considered based on the business approaches of the rice production stakeholders.
Tóm tắt: Tốc độ khử màu của Reactive Blue 21 bởi axít peracetic trong dung dịch được khảo sát ở pH = 6,0. Các thí nghiệm được thực hiện với nồng độ axít peracetic trong khoảng 1 ÷ 3 mM. Diễn biến phản ứng được theo dõi thông qua đo biến thiên độ hấp thụ quang ở bước sóng hấp thụ cực đại của Reactive Blue 21 tại 660 nm. Kết quả nghiên cứu cho thấy rằng sự mất màu được thực hiện qua hai cơ chế là phản ứng không xúc tác và phản ứng tự xúc tác. Trên cơ sở các dự liệu thực nghiệm, mô hình động học bậc hai đã được đề xuất cho hai phản ứng.Từ khóa: Reactive Blue 21, Axít peracetic, động học, xúc tác, xử lý màu. Tổng quan Xử lý màu nước thải nói chung và màu dệt nhuộm nói riêng là hướng nghiên cứu được quan tâm trên thế giới. Nhiều phương pháp đã được nghiên cứu như hấp phụ, keo tụ -tạo bông, keo tụ điện hóa, trao đổi ion, lọc thẩm thấu ngược, xử lý sinh học, ôxi hóa hóa học, ôxi hóa tiên tiến [1,2]. Nước thải dệt nhuộm có thành phần ô nhiễm tương đối đa dạng bao gồm cặn lơ lửng, kim loại nặng, chất màu bền, các chất hữu cơ, pH cao [3]. Do đó, hệ xử lý nước thải dệt nhuộm thường là tổ hợp của các phương pháp tiền xử lý, xử lý chính, và sau xử lý. Đến nay, xử lý sinh học vẫn đang được áp dụng phổ biến để xử lý nước thải dệt nhuộm. Tuy nhiên, phương pháp này chưa xử lý được triệt để độ màu nên cần thêm giải pháp ôxi hóa để phá màu bền vững. Nhằm tìm kiếm chất ôxi _______ ĐT.: 84-904119229.Email: lechieu@vnu.edu.vn https://doi.org/10.25073/2588-1094/vnuees.4106 hóa màu hiệu quả và thân thiện môi trường, đề tài này đánh giá khả năng khử màu Reactive Blue 21 (RB21) bằng axít peracetic (PAA). Phương pháp nghiên cứuPhản ứng giữa RB21 và PAA được thực hiện trong dung dịch với thể tích 1 L có khuấy từ ở pH = 6,0 và nhiệt độ 25 ± 2 o C. Nồng độ PAA được khảo sát trong khoảng 1 đến 3 mM. Nồng độ màu ban đầu khoảng 25 mg/L. Tốc độ mất màu được theo dõi thông qua đo biến thiên hấp thụ quang của RB21 ở bước sóng 660 nm.Trong nghiên cứu, màu RB21 sử dụng có nguồn gốc từ Trung Quốc có độ tinh khiết 95 %. PAA được điều chế trực tiếp trong phòng thí nghiệm từ phản ứng giữa CH 3 COOH đặc với H 2 O 2 (30 %) theo tỉ lệ thể tích 1,5: 1 theo phản ứng sau: CH 3 COOH + H 2 O 2 = CH 3 COOOH + H 2 O
Sokolow – Lyon index in detection of left ventricular hypertrophy is a hard limited index, so the clinical manifestation of the disease can be ignored when the measured index is near the threshold. Several proposed studies incorporate multiple index to improve diagnostic quality. However, the process of examination and diagnosis will be longer due to the need to collect more data. To solve this problem, the paper proposes a method of classifying left ventricular hypertrophy using fuzzy logic combining with digital signal processing techniques. The proposed method mainly uses the Sokolov-Lyon index (SV1+RV5/V6 ≥ 35 mm) for major changes in ECG signal but with four soft thresholds corresponding to the different clinical manifestations of the disease. In addition, a program is written in C++ language with QT Creator compiler also is developed to implement the algorithm. From there, the doctors can refer and propose to the patient's treatment regimen. Keywords ECG, left ventricular hypertrophy, signal processing, fuzzy logic. References [1] Malcolm S. Thaler, The only EKG book, seventh ed. Lippincott Williams & Wilinks, Philadelphia, 2012. [2] Vakili BA, Okin PM, Devereux RB, Prognostic implications of left ventricular hypertrophy, Am Heart J, 141(3) (2001) 334-341.https://doi.org/10.1067/mhj.2001.113218.[3] Tran Do Trinh, Tran Van Dong, How to read EGC signal, Medical Publishing House, 2011 (in Vietnamese).[4] Himanshu Gothwal1, Silky Kedawat1, Rajesh Kumar, Cardiac arrhythmias detection in an ECG beat signal using fast fourier transform and artificial neural network, J. Biomedical Science and Engineering 4 (2011) 289-296.https://doi.org/10.4236/jbise.2011.44039.[5] El-Sayed A. El-Dahshan, Genetic algorithm and wavelet hybrid scheme for ECG signal denoising, Journal of Telecommunications Systems 46(3) (2011) 209-215.https://doi.org/10.1007/s11235-010-9286-2.[6] C. Li, C. Zheng, and C. Tai, Detection of ECG characteristic points using wavelet transforms, IEEE Trans.Biomed. Eng 42(1) (1995) 21-28.https://doi.org/10.1109/10.362922.[7] A.K.M. Fazlul Haque1, Md. Hanif Ali1, M. Adnan Kiber2 and Md. Tanvir Hasan, Detection of small variations of ECG features using Wavelet, ARPN Journal of Engineering and Applied Sciences 4(6) (2009) 27-30.[8] Krimi Samar, Ouni Kas, Noureddine Ellouze, Using Hidden Markov Models for ECG Characterisation, Hidden Markov Models, Theory and Applications, 4 (2011) 151-165.https://doi.org/10.5772/13916.[9] Van Ngoc Tuyet, Bang Ai Vien, Nguyen Van Tri, Medical Journal Ho Chi Minh city, Diagnosis of left ventricular hypertrophy by ECG I 15(1) (2011) 135-140 (in Vietnamese).[10] Buckley, James J., Eslami, Esfandiar, Introduction to Fuzzy Logic and Fuzzy Sets, Physica-Verlag Heidelberg, Berlin, 2002. [11] Phan Xuan Minh, Nguyen Doan Phuoc, Fuzzy Control Theory, Science and Technics Publishing House, Ha Noi, 2006 (in Vietnamese).
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