Horng-Guang Leu

Modelling the steady-state effluent characteristics of the TNCU process under different return mixed liquid

Abstract The Activated Sludge Model No. 2d (ASM2d) was employed and modified to predict the effluent qualities of the modified enhanced biological phosphate removal (EBPR) system – TNCU. The TNCU process was composed of anaerobic/anoxic/oxide (A2O) process and rotating biological contactors (RBC) in each reactor. There were three modifications for the model in this study: (1) the biosorption effect of the soluble COD, (2) the ammonification of the organic nitrogen in influent wastewater, and (3) the growth of the heterotrophic organisms in the anaerobic tank. The influent wastewater qualities were fixed, the ratios of return sludge and SRT were 0.5 and 11 days, and the model plant was operated at three different mixed liquid recycling ratios (MLRR, 0.5, 1.25, 2). When a steady state was reached, the comparisons between the measured values and the model predicted values in each test were made. It shows a good consistency between them. According to the consistent results, the biosorption effect of the soluble COD and the ammonification of the organic nitrogen in influent wastewater were the important effects in activated sludge system. Additionally, the heterotrophic organisms might grow in the anaerobic tank. The heterotrophic organisms, phosphorus accumulating organisms and autotrophic organisms would decrease in the anaerobic tanks because the lysis reactions were the major reactions in the anaerobic tanks. They would increase in the aerobic tanks. Furthermore, it was indirectly proved that the denitrifying PAOs existed in the EBPR system.

Novel modeling concept for evaluating the effects of cadmium and copper on heterotrophic growth and lysis rates in activated sludge process.

A new modeling concept to evaluate the effects of cadmium and copper on heterotrophic growth rate constant (mu(H)) and lysis rate constant (b(H)) in activated sludge was introduced. The oxygen uptake rate (OUR) was employed to measure the constants. The results indicated that the mu(H) value decreased from 4.52 to 3.26 d(-1) or by 28% when 0.7 mg L(-1) of cadmium was added. Contrarily the b(H) value increased from 0.31 to 0.35 d(-1) or by 11%. When adding 0.7 mg L(-1) of copper, the mu(H) value decreased to 2.80 d(-1) or by 38%. The b(H) value increased to 0.42 d(-1) or by 35%. After regression, the inhibitory effect was in a good agreement with non-competitive inhibition kinetic. The inhibition coefficient values for cadmium and copper were 1.82 and 1.21 mg L(-1), respectively. The relation between the b(H) values and heavy metal concentrations agreed with exponential type well. The heavy metal would enhance b(H) value. Using these data, a new kinetic model was established and used to simulate the degree of inhibition. It was evident that not only the inhibitory effect on mu(H) but also that the enhancement effect on b(H) should be considered when heavy metal presented.

Evaluating Taiwan's air quality variation trends using grey system theory

Abstract According to geographical characteristics and air quality conditions, the Taiwan Environmental Protection Agency has divided the island into 7 air quality regions (AQRs) including Northern, Chu‐Miao, Central, Yun‐Chia‐Nan, Kao‐Ping, I‐lan and Hwa‐Tung AQRs. The grey relational grade (GRG) of all AQRs and nationwide grade were calculated to comprehend the level of contamination. Then the grey model GM (0, N) was used to evaluate the effects of 5 primary contaminants on air quality. The results indicated that the ranking of air quality for the 7 AQRs from the best to the worst were as follows: Hwa‐Tung > I‐lan > Chu‐Miao > Northern > Yun‐Chia‐Nan > Central > Kao‐Ping. The 5 most common contaminants from the greatest to the least were as follows: CO > SO2 > NO > O3 > PM10.

MODELLING THE STABLE EFFLUENT QUALITIES OF THE A2O PROCESS WITH ACTIVATED SLUDGE MODEL 2d UNDER DIFFERENT RETURN SUPERNATANT

Abstract A modified mathematical model based on the Activated Sludge Model No. 2d (ASM2d) was established to describe the effluent qualities of the enhanced biological phosphate removal (EBPR) system ‐ A2O. There were three modifications to the model in this study: (1) the biosorption effect of the soluble COD, (2) the hydrolysis of the organic nitrogen in influent wastewater, and (3) the growth of heterotrophic organisms in the anaerobic tank. The A2O process is composed of an anaerobic/anoxic/oxide process which removes biological phosphorus with simultaneous nitrification‐denitrification. The influent wastewater quality and quantity were fixed, the ratios of return sludge and sludge retention time were 0.25 and 12 days, and the model plant was operated at three different mixed liquid recycling ratios (MLRR, 0.5, 1.25, 2). When a steady state was reached, comparisons between the measured values and predicted values were made for each test. A good consistency between the test values and simulation values was shown. According to our results, the biosorption effect of the soluble COD and the hydrolysis of the organic nitrogen in influent wastewater are the important qualities in activated sludge systems. Additionally, heterotrophic organisms might grow in the anaerobic tank. Furthermore, it was indirectly proved that the denitrifying PAOs existed in the EBPR system.

Predicting hourly ozone concentration in Dali area of Taichung County based on multiple linear regression method

In this study, multiple linear regression (MLR) method was used to establish the rela- tionship between the O3 at time t + 1 and other indices including hourly air pollutant concentra- tions and meteorological conditions at time t. Then O3 was predicted using the obtained best-fitting MLR. The results indicated that the relationship between the O3 at time t + 1 and other indices including hourly air pollutant concentrations and meteorological conditions at time t agreed with MLR well, The values of mean absolute percentage error (MAPE), correlation co- efficient (R), coefficient of determination (R 2 ), mean square error (MSE), and root mean square error (RMSE) were 29.09 %, 0.95, 0.90, 45.33, and 6.73, respectively when determining the best-fitting equation. In addition, MLR could predict hourly ozone concentrations successfully. The values of MAPE, R, R 2 , MSE, and RMSE were 10.37 %, 0.93, 0.86, 0.33, and 0.57, respec- tively when predicting. It also indicated that the hourly air pollutant concentrations and mete- orological conditions at time t could be applied on the prediction of ozone of time t +1.

Induced pressure-variation transport in unconfined aquifer

Abstract The purpose of this study is to develop a numerical model and simulate the behavior of the head potential fluctuation in subsurface flows. Numerical and analytical solutions are presented. Impacts of storativity and porosity on the head potential fluctuation are investigated in this paper. It is found, in one‐dimensional subsurface flows, that porosity and storativity play an important role in the propagation of the head potential fluctuation. In addition, an asymptotic behavior of the head potential fluctuation is not reached until the head propagation travels more than three‐fourths of the total length of the aquifer.

EFFECTS OF OXYGEN ON THE NITROGEN TRANSFORMATIONS IN A SLOW-FLOWING OPEN CHANNEL†

This study investigated the effects of dissolved oxygen ( DO ) concentration and flow conditions on the conversion rates and pathways of nitrogenous compounds in an pilot open channel. Ammonium sulfate and glucose were added externally as the substrates in the investigation. The experimental results showed that under conditions of constant flow velocity and DO concentration above 1 mg/1, the removal rates of total nitrogen (including nitrite, nitrate and ammonium nitrogens) varied linearly with the removal rates of ammonium nitrogen. Comparison of the removal rate for each individual nitrogenous component reveals the following order of removal rates: ammonium nitrogen>total nitrogen>nitrate nitrogen> nitrite nitrogen. Moreover, the nitrite concentration was found to increase in all tests and the nitrate concentration was increased only when the DO concentration was within the range of 3 to 5 mg/l. In contrast, when the DO concentration was less than 1 mg/l, all nitrogenous compounds were removed and the following order of removal rates of nitrogenous compounds was observed: total nitrogen>nitrate nitrogen>nitrite nitrogen>ammonium nitrogen. The results indicated that the conversion pathways of nitrogenous compounds can be divided into four different types depending on the DO concentration level. The test results also revealed that an increase in the flow velocity significantly influenced the conversion rates of nitrogenous compounds. While a V-shaped relation of the removal rates of total nitrogen vs the Reynolds numbers was observed for low DO below 1.5 mg/1, an inverted V-shaped relation occurred at high DO above 5 mg/1.