Hong-Duck Ryu

Application of struvite precipitation in treating ammonium nitrogen from semiconductor wastewater

Struvite precipitation was applied to the removal of NH(4)-N in semiconductor wastewater. Batch experiments were conducted to examine the effects of final pH, magnesium and orthophosphate dosages and the initial influent concentrations of NH(4)-N and F on the removals of NH(4)-N and PO(4)-P by forming struvite deposits. pH was an important parameter in the simultaneous removals of ammonium nitrogen and orthophosphate. In struvite precipitation, the amount of orthophosphate in the solution affected NH(4)-N removal much more than that of magnesium ions in some cases. It was revealed that the low and high initial concentrations of NH(4)-N and F inhibited NH(4)-N and PO(4)-P removal efficiencies in struvite precipitation, respectively. We also evaluated field-scale treatment plant incorporated by struvite precipitation process. On semiconductor wastewater with an NH(4)-N concentration of 155 mg/L, the results obtained showed that the incorporation of the struvite precipitation process brought about a high NH(4)-N removal efficiency of over 89% on average.

Effect of mixing on spontaneous struvite precipitation from semiconductor wastewater

The objective of this study was to investigate on the effect of mixing intensity (G) and mixing duration (t(d)) on struvite precipitation in the chemical mechanical polishing (CMP) wastewater generated from the semiconductor manufacturing process. Batch-scale experiments revealed that struvite crystallization was affected by both G and t(d). The mixing effect was to enhance the mass transfer of solute to the crystals in the process, resulting in the improvement of struvite crystallization and growth. By forming struvite, removal efficiencies of N and P increased logarithmic with the multiple values of G and t(d), i.e., Gt(d). Insufficient mixing energy with the Gt(d) value less than 10(5) caused an increase in the formation potential of unexpected precipitate unlike to pure struvite, causing a decrease in removal efficiencies of N and P in the process. At the Gt(d) value over 10(6), struvite precipitation was not restricted by fluoride, of which high level inherently contained in the CMP wastewater. The study results can be taken into consideration in the design and operation of the struvite precipitation process for both nutrient (N and P) removal and recovery.

Long term operation of pilot-scale biological nutrient removal process in treating municipal wastewater.

The performance of a pilot-scale biological nutrient removal process has been evaluated for 336 days, receiving the real municipal wastewater with a flowrate of 6.8m(3)/d. The process incorporated an intermittent aeration reactor for enhancing the effluent quality, and a nitrification reactor packed with the porous polyurethane foam media for supporting the attached-growth of microorganism responsible for nitrification. The observation shows that the process enabled a relatively stable and high performance in both organics and nutrient removals. When the SRT was maintained at 12 days, COD, nitrogen, and phosphorus removals averaged as high as 89% at a loading rate of 0.42-3.95 kg COD/m(3)d (corresponding to average influent concentration of 304 mg COD/L), 76% at the loading rate of 0.03-0.27 kg N/m(3)d (with 37.1mg TN/L on average), and 95% at the loading rate of 0.01-0.07 kg TP/m(3)d (with 5.4 mg TP/L on average), respectively.

Treatment of N, P of Auto-Thermal Thermophilic Aerobic Digestion Filtrate with Struvite Crystallization

Recently, auto-thermal thermophilic aerobic digestion (ATAD) has a great attention for destruction of wasted sludge biomass in wastewater treatment plant. Reduction of sludge concentration has been successfully achieved with pilot scale ATAD and ceramic filtration process in field condition. However, high concentration of COD, total nitrogen (TN) and total phosphorus (TP) was observed in filtrate, which should be treated before recirculation of filtrate to biological wastewater treatment plant. This study was focused on removal of nitrogen and phosphorus contained in the filtrate of ATAD, using struvite crystallization method. The effect of operational and environmental parameters (such as, N, P and Mg ion concentration and molar ratio, pH, reaction time, agitation strength, seed dosage, and reaction temperature) on the treatment of TN and TP with struvite crystallization were evaluated. Magnesium (as MgCl26H2O) and phosphorus (as K2HPO4) ions were, if necessary, added to increase nitrogen removal efficiency by the crystal formation. Average concentration of NH4-N and PO4-P of the filtrate were 1716.5 mg/L and 325.5 mg/L, respectively. Relationship between removal efficiencies of nitrogen and phosphorus and molar ratios of Mg and PO4-P to NH4-N was examined. Crystal formation and nitrogen removal efficiencies were significantly increased as increasing molar ratios of magnesium and phosphorus to nitrogen. As molar ratio of Mg : PO4-P : NH4-N were maintained to 2 : 1 : 1 and 2 : 2 : 1, removal efficiencies of nitrogen and phosphorus were 71.6% and 99.9%, and 93.8% and 98.6%, respectively. However, the effect of reaction time, mixing intensity, seed dose and temperature on the struvite crystallization reaction was not significant, comparing to those of molar ratios. Settled sludge volume after struvite crystallization was observed to be reduced with increase of seed dose and to be increased at high temperature.

Effect of Calcium Sources for the Treatment of Wastewater Containing High Fluoride

As production of LCD increases, it has become necessary to find an economically efficient way of treating LCD wastewater with high concentration of fluoride. This study focuses on the calcium sources : CaCl2, Ca(OH)2 and CaCO3 for the treatment of the LCD wastewater including high concentration of fluoride. Of course considering removal efficiency and economical aspect, study is continued. Then this study have objective giving aid to field. Consequently, each calcium sources removal efficiency was measured in various pH, calcium dosage, reaction time, and mixing intensity. The optimum operational conditions for CaCl2 were found to be pH of 7, calcium dosage of 0.4[Ca] / [F] (mol / mol), 1 hr of operation and 200 rpm of mixing intensity. For Ca(OH)2, they were pH of 7, calcium dosage of 30 mL/L, 1 hr of operation, and 200 rpm of mixing intensity. While CaCO3 had operational conditions of pH of 4, calcium dosage of 30 mL/L, 1 hr operation and 200 rpm of mixing intensity. But it is recommended to use calcium sources according to various field conditions.

Effect of Sludge Age on the Toxicity of Cr 6+ , Zn 2+ , and Cd 2+ in INT-Dehydrogenase Assay

This study was initiated to elucidate the relation between the toxicity of , , and and sludge age (Solids retention time, SRT). The effect of SRT on the toxicity of , , and in activated sludge system was investigated with INT-dehydrogenase assay. Experimental results showed that the inhibitory effects of , , and were reduced as the sludge age increased from SRT 5 d to SRT 25 d. It is noteworthy that the experimental results enabled to determine the relative toxicity of the tested metals depending on the sludge age. At the SRT of 5 and 9 days, the order of toxicity of the three metals to the activated sludge was > > (the value of , , and was 16.15, 25.90, and 32.49 mg/L, respectively) and > > (the value of , , and was 39.12, 27.93, and 42.31 mg/L, respectively), respectively. However, the toxicity of three metals was almost same at the SRT of 14 and 25 days (the range of in SRT 14 and 25 days was from 49.80 mg/ L to 53.44 mg/L among three heavy metals). This results would be explained by that the quantity of biopolymer formed in short SRT was small, whereas that in long SRT was large. Consequently, it is recommended that sludge age be maintained at long SRT in order to avoid the toxicity inhibition of heavy metals such as , , and .

Recovery and Recycling of Nitrogen and Phosphorus as Struvite from Livestock Excreta

This study evaluated the feasibility of recovering and recycling nitrogen (N) and phosphorus (P) from livestock excreta as struvite (

Determination of Veterinary Antibiotic Residues: IV. Comparable Analytical Methods with EPA Methods 1694_A Review

MgNH_4PO_4{\cdot}6H_2O

Enhancing struvite precipitation potential for ammonia nitrogen removal in municipal landfill leachate

) in South Korea. Our experimental results showed that struvite precipitation was a very effective way to recover N and P from livestock ex...

Nitrogen removal from low carbon-to-nitrogen wastewater in four-stage biological aerated filter system

Abstract In this study, 16 antibiotics were selected from among the top 30 veterinary antibiotics sold in South Korea in 2014, as well as from among the pharmaceuticals targeted by EPA method 1694, in order to review analytical methods for the detection of trace levels of antibiotics in environmental samples: surface water, soils, animal origin foods, and manures. LC-MS/MS was heavily used. In the chromatography for the detection of the selected antibiotics, the C18 column was mostly used at the temperature of 30~40°C. Water and methanol/acetonitrile were commonly chosen as a nonpolar and a polar mobile phase, respectively. Gradient elution was applied to separate multiclass antibiotics. Volatile additives, such as formic acid, acetic acid, and ammonium acetate were mixed with the mobile phase to improve the ionization efficiency of analytes and the sensitivity in MS detection. Electrospray ionization (ESI) was widely used in the LC-MS/MS and positive ionization was preferred to determine the selected antibiotics. A protonated [M+H] molecule was selected as a precursor ion, and its two transitions were analyzed, one for quantitative measurement and the other for confirmation. This study reviewed linearity of the calibration curve, recovery, repeatability, method detection limits (MDLs), and method quantification limits (MQLs) for each target compound used to validate the developed analytical methods.