• Journal of Korean Society of Water and Wastewater
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• v.28 no.4
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• pp.479-489
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• 2014

Membrane backwashing waste shows seasonally different characteristics and it has bad settleability differently from general backwashing waste in water treatment plant. When chemicals was injected to membrane backwashing waste, the settleability was better than chemicals was not injected. However, when settled lower sludge was not discharged, flowing sludge continuously was concentrated over a certain surface and floatation penomena occurred according to flowing velocity. When the lower sludge was discharged continuously in the thickener to prevent floatation penomena of turbidity materials, the depth of sludge surface was the least and the settleability increased.

• Proceedings of the Membrane Society of Korea Conference
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• 1993.10a
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• pp.65-67
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• 1993

도금공업은 공업기반기술의 하나로서 기계 및 소재산업의 최종 마무리 공정으로 중요시 되고 있으나 운전중 기술의 특성에 의하여 중금속이 함유된 도금폐수를 방출하게 되어 인체 및 생태계에 매우 유해한 산업중의 하나이다. 기존의 도금폐수처리 방븝으로 침전 응집법이 있으나 이는 사용되는 약품의 양이 많고, 슬러지를 배출하여 2차 공해를 유발하므로 완전한 처리 방법이라 할 수 없다. 본 연구에서는 이러한 국내 도금폐수의 현황을 조사한바 도금폐수중 배출양이 가장 많은 아연계폐수를 대상으로 RO Membrane를 사용하여 실험하였다. RO Membrane으로 실험하였을때 아연이온은 Retentate로 분리 농축되고 Permeate는 재생수로 순환 사용할 수 있는 도금폐수의 무배출 처리공정(Zero-Discharge System) 개발을 존 연구의 목적으로 하였다.

• Journal of Environmental Science International
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• v.23 no.1
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• pp.97-104
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• 2014

The sludge flotation/thickening apparatus equipped a micro-bubble generating pump was used to investigate micro-bubble generating properties on operational parameters. We evaluated micro-bubble generating properties as results to be operated the apparatus by operational parameters which are pump discharge pressure, air/water ratio(A/W ratio), air flow rate, and water flow rate. Micro-bubble generating efficiencies in pumps without recycling flow and with 50% of recycling flow was found to be very efficient on optimum A/W ratio from 1.06 to 3.62% and optimum A/W ratio from 1.05 to 4.06%, respectively. In condition of 3.6% of A/W ratio, we showed that the apparatus could be generated 36,000 ppm of micro-bubble concentration to be optimum treatment efficiency in sludge thickening process.

• Journal of Environmental Science International
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• v.15 no.1
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• pp.77-84
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• 2006

An effective technique of sludge separation is required for excess sludge of sewage or wastewater plant. The separation of bulking sludge of paper manufacturing plant was studied using DAF(Dissolved Air Flotation) system. The effects of parameters such as nozzle type, A/S(air/solid) ratio. pressure, injection time of pressured water and saturation time were examined. The results showed that the best nozzle type was flat which had small orifice hole, The optimum A/S ratio and pressure were $7.070\times10^{-3}$(recycle ratio of pressured water $20\%$) and 5atm, respectively. Injection times of pressurized water around 20-25 sesc and flotation time of 30 min appeared to be optimal for the DAF operation. The order of performance of packing was 18 mm > 22 mm > 32 mm.

• Journal of Wetlands Research
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• v.17 no.4
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• pp.414-420
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• 2015

Nitrogen is one of main causes to induce eutrophication of water system and one of contaminants that must be treated for protection of water system. In this study, it was intended to identify a method to increase operation efficiency of municipal wastewater treatment plant (MWTP) by treating high concentration nitrogen. A laboratory scale reactor was operated by using sludge thickener supernatant in the MWTP. During operation of the laboratory scale reactor, it was intended to induce stable nitritation and analyze effects of related operation factors. As results, it was shown that the nitiritation could be induced artificially through control of retention time and sections where the stable nitiritation was induced were identified also. In particular, highly efficient nitrite conversion efficiency near 90% was identified in condition of 1 day retention time. Especially, it was shown that ammonium nitrogen load affected ammonium nitrogen removal efficiency and nitrite conversion efficiency. In the condition of high ammonium nitrogen load, the nitrite conversion efficiency and the ammonium nitrogen removal efficiency decreased. On the contrary in the condition of low ammonium nitrogen load, it was found that the nitrite conversion efficiency decreased. It means that control of ammonium nitrogen concentration and its retention time is needed for the nitritation. It is considered that for the sewage containing high load nitrogen in sludge treatment process as like the sludge thickener supernatant, the nitritation can be applied, which can be suggested as a modification method of MWTP.

• Journal of Korean Society on Water Environment
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• v.26 no.2
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• pp.349-355
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• 2010

Electroflotation (EF) was conducted for activated sludge thickening to investigate the effects of sludge SVI (sludge volume index) and chemical conditioning. Return sludge samples were used for the experiment, which were collected from municipal wastewater treatment plants. The performance of sludge thickening was significantly dependent on sludge SVI. For the sludges with SVI values in a range from 50 to about 150 mL/g, the maximum float content decreased rapidly from 8.4 to 3.5% and flotation compressibility followed the same pattern. In cases of sludges with SVI higher than 150 mL/g, those results showed low content levels without large changes. Gas/solids ratio tended to increase with an increase in SVI. When polyelectrolyte was added into sludges for the conditioning, compressibility increased up to 75% and gas/solids ratio was reduced up to about 35% under the condition of microbubble production rate of 530 mL/h, however, there was no consistent effect of chemical conditioning on the maximum float solids content; some cases were positive but the others negative. It was expected that the optimum dose of electrolyte depends on sludge SVI and an excessive chemical dose causes a performance deterioration of flotation thickening.

• Korean Journal of Microbiology
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• v.35 no.4
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• pp.283-288
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• 1999

The effect of dissolved oxygen(DO) concentration on the growth of Pseudomonas aeruginosa and it's mutant M-10 was studied the growth kinetics and the possibility of waste treatment for reducing the amount of excess sludge. Different DO concentrations on the growth of wild type Pseudomonas aeruginosa affected to cellular yields, decreasing with increasing DO concentrations. Under these conditions, the maximum 14 folds decrease of cellular yield was achieved at 90 ppm DO levels by screened, being able to reduce their cellular yields under low DO concentration. The optimum mutation conditions were obtained by the treatment of NTG mutagen at 30${\circ}C$ for 1 hr. The growth characteristics of the selected mutant M-10 showed the same as the wild type growth kinetics. However, cellular yields are significantly decreased to 55% compared with those of wild type under DO concentrations increased. We, therefore, expect the application of the mutants to waste treatment for reducing excess sludge.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.2
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• pp.203-212
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• 2019

Disposal nonconformity of radioactive wastes refers to radioactive wastes that need to be treated, solidified and packaged during operation or decommissioning of NPPs, and are typically exemplified by particulate radioactive wastes with dispersion characteristics. These wastes include the dried powders of concentrated wastes generated in the process of operating NPPs, slurry and sludge, various powdered wastes generated in the decommissioning process (crushed concrete, decontamination sludge, etc.), and fine radioactive soil, which is not easy to decontaminate. As these particulate wastes must be packaged so that they become non-dispersive, they are solidified with solidification agents such as cement and polymer. If they are treated using existing solidification methods, however, the volume of the final wastes will increase. This drawback may increase the disposal cost and reduce the acceptability of disposal sites. Accordingly, to solve these problems, this study investigates the pelletization of particulate radioactive wastes in order to reduce final waste volume.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.2
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• pp.161-170
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• 2014

It is essential to decrease energy consumption and excess sludge to economically operate sewage treatment plant. This becomes more important along with a ban on sea dumping and exhaustion of resource. Therefore, many researchers have been study on energy consumption reduction and strategies for minimization of excess sludge production from the activated sludge process. The aeration cost account for a high proportion of maintenance cost because sufficient air is necessary to keep nitrifying bacteria activity of which the oxygen affinity is inferior to that of heterotrophic bacteria. Also, additional costs are incurred to stabilize excess sludge and decrease the volume of sludge. There were anoxic, aerobic, membrane, deairation and concentration zone in this MBR process. Continuous aeration was provided to prevent membrane fouling in membrane zone and intermittent aeration was provided in aerobic zone through ammonia sensor. So, there was the minimum oxygen to remove $NH_4-N$ below limited quantity that could be eliminated in membrane zone. As the result of this control, energy consumption of aeration system declined by between 10.4 % and 19.1 %. Besides, we could maintain high MLSS concentration in concentration zone and this induced the microorganisms to be in starved condition. Consequentially, the amount of excess sludge decrease by about 15 %.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.6
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• pp.800-808
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• 2005

It is required to propose an alternatives for appropriate sludge treatment owing to persistent construction of sewage treatment plant and increase of sewage sludge quantity. In order to treat sludge more efficiently, the methods which reduce the cost of sludge treatment have been studied such as sludge reduction and conditioning. Especially ozone treatment reduces solid quantity and improves separation of solid-liquid at the same time. Therefore ozone treatment have a positive effect on reduction and stabilization of sludge. So, this study applied ozone to sewage sludge and induced cell destruction of sludge. By comparing with the correlation between thickening and dewatering, and evaluating moisture content and solubilization of cake, this study verificates the effect of process improvement for ozone pre-treatment. In J-STP case, according to ozone dose solid flux increased about 12 times from $1kg/m^2{\cdot}h$ to $12kg/m^2{\cdot}h$. Also this plant were capable to shorten thickening time from 40 minutes to 6~7 minutes. Thus it is expected to reduce volume and retention time of thickener. On pH effect factor, dewatering at pH4 was more than at pH11, $3.05{\times}10^{11}$ and $3.82{\times}10^{11}(m/kg)$. But effect of pH was analogous to ozone, $2.81{\times}10^{11}(m/kg)$. The effect of pH on thickening was similar to law sludge, $0.68(kg/m^2{\cdot}h)$, and the effect of ozone injection on thickening was the biggest, $3.45(kg/m^2{\cdot}h)$. The COD solubilization rate improved from about 5 to 30%. So it is judged that we are able to utilize most solubilized sludge to another sewage treatment plants.