• Journal of Korean Society of Water and Wastewater
• /
• v.18 no.5
• /
• pp.598-607
• /
• 2004

In this study, the effects of two pre-treatment processes were observed prior to membrane filtration: pre-coagulation and pre-ozonation. To compare the effect of two above-mentioned pre-treatments, we adopted the four schemes: first one is direct membrane filtration of river surface water, second one is membrane filtration after pre-coagulation, third one is membrane filtration after pre-ozonation and fourth one is membrane filtration after pre-coagulation and pre-ozonation. There are two exceptional characteristics in applied processes. One is the usage of the MF membrane which has high ozone resisting characteristic. Therefore, ozone resides in membrane module during filtration. The other is adoption of Jet Mixed Separator (JMS) as coagulation-sedimentation process. The change in transmembrane pressure and permeate water quality were also examined. As a result, considering the filtration performance efficiency and permeate water quality, the process composed of filtration with combination of both pre-coagulation and pre-ozonation was proved most effective. The improved efficiency was due to the reduction of loading rate of fouling inducing materials to membrane module by coagulation process as well as variable reactions, such as degradation, particle destabilization and coagulation, occurred by residual ozone in membrane module. The additional effect of pre-coagulation before pre-ozonation is suppression of AOC, one of the by-products induced by ozonation. Therefore, combination of pre-coagulation and pre-ozonation is the effective process to overcome the major de-merit of ozonation i.e. by-products formation.

• Journal of Environmental Science International
• /
• v.8 no.6
• /
• pp.717-724
• /
• 1999

This experiment was performed on three parts with prepared coagulants. (1) The characterization of coagulation for PACI coagulants. (2) Comparison of the characterization of coagulation with PAS and PACI coagulants. And (3) Comparison of the characterization of coagulation for the addition of calcium with PACI. Coagulation experiments were conducted with several dosages and pH for each coagulants. For the characterization of coagulation with PACI coagulants, coagulation of Nakdong river waters with three PACls (r=2.0, 2.2, 2.35) showed that the effectiveness of the three coagulants can be considered as r=2.2 > 2.0 > 2.35 which are also the order of higher polymeric aluminum contents. For the comparison of the characterization of coagulation for PAS and PACI coagulants, PAS (r=0.75) coagulants was more effective than other coagulant for the removal of organic matters by sweep floc mechanism with $A;(OH)_{3(S)}$. For comparison of the characterization of coagulation for the addition of calcium with PACI, the presence of divalent cation like $Ca^{2+}$ was supposed to influence the complex formation of organic anions. From the result of test on coagulation at various pH ranges, the PACI was least affected by the coagulation pH, and the addition of calcium to PACI was very effective for the removal of turbidity and organic materials over broader pH range (pH 4-9).

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2003.05b
• /
• pp.355-356
• /
• 2003

Coagulation is a process whereby particles collide with one another due to their relative motion, and adhere to form large particles. Coagulation caused by the random Brownian motion of particles is called Brownian coagulation. Many properties, such as light scattering, electrostatic charges, toxicity, as well as physical processes, including diffusion, condensation and thermophoresis depend strongly on their size distribution. Therefore, Brownian coagulation is substantially important in atmospheric science, combustion technology, inhalation toxicology and nuclear safety analysis. (omitted)

• Journal of Korean Society of Water and Wastewater
• /
• v.18 no.6
• /
• pp.785-793
• /
• 2004

Coagulation has been investigated for pretreatment of low-pressure membrane systems such as microfiltration and ultrafiltration. Coagulation pretreatment can reduce foulants (particles and organic matter) prior to membrane filtration. However, when in-line coagulation or submerged type of filtration is used, flocculent aggregates could act as a foulant depending on concentrations and specific properties of floc. A natural water and three synthetic waters were used to investigate effects of coagulation pretreatment and presence of flocculent aggregates on membrane fouling. Coagulation pretreatment shows that foul ants were effectively removed during coagulation and the formed cake layer on the membrane surface had less resistances compared to raw natural water. In addition, little difference in membrane fouling was found by flocculent aggregates from the natural water. Interestingly, however, the results by three synthetic waters indicated that flocculent aggregates could have adverse effects on membrane fouling in a specific condition.

• Environmental Engineering Research
• /
• v.11 no.1
• /
• pp.45-53
• /
• 2006

Conventional coagulation is still the main treatment process for algae removal in water treatment. The coagulation efficiency can be significantly improved by the preoxidation of algae-containing water. Jar test was conducted to determine the optimal condition for the removal of diatoms, especially Cyclotella sp. by preoxidation and the subsequent coagulation. The effects of various concentration of PAC (Polyaluminum chloride) on coagulation with and without preoxidation using chlorine or potassium permanganate at different pHs (7.7 and 9.0) were evaluated. At pH 7.7, preoxidation with 2ppm $Cl_2$ followed by coagulation with 7.5 ppm PAC coagulant could reduce Cyclotella sp. concentration by 86%. At pH 9.0, preoxidation with 1 mg $KMnO_4/L$ followed by coagulation with 12.5 ppm PAC coagulant reduced Cyclotella sp. concentration by 85%. Non-linear regression was applied to determine the optimal condition. At pH 7.7 and 9.0, R was over 0.9, respectively. The pH of algal blooming water is over 9.0. Algae (diatom; Cyelotella sp.) can be controlled in the following ways: preoxidation with 1 mg $KMnO_4/L$ followed by coagulation with 12.5 ppm PAC coagulant can remove 80% algae from water. If water pH is adjusted to 7.7, it was expected that less amount of coagulant (7.5 or 10 mg PAC /L) after preoxidation ($Cl_2$ 2 ppm or $KMnO_4$ 0.33, 1 ppm) would be needed to achieve similar level of algae removal. The oxidation with 0.33ppm $KMnO_4$ followed by coagulation with 7.5 ppm PAC coagulant was preferable due to cost-effectiveness of treatment condition and color problem after treatment.

• Journal of Environmental Health Sciences
• /
• v.27 no.4
• /
• pp.93-98
• /
• 2001

Wastewaters produced in textile industrial processes contain dyes which are not easily amenable to biological treatment. The object of this study is to determine the post-treatment system of biological process for the textile wastewater by comparing three different types of chemical process, which were 1) post-treatment by ozone or UV, 2) post-treatment by coagulation,3) post-treatment by ozone or UV followed by coagulation. In an application ozone or UV as a post-treatment, color was generally decreased with time, however, SCOD removal effect was not that good. When coagulation was used as point-treatment process, the effluent quality was satisfying. Therefore, the application of coagulation process as a post-treatment of biological process would be more desirable than that as a ozone or UV.

• Journal of Environmental Science International
• /
• v.21 no.9
• /
• pp.1043-1051
• /
• 2012

Coagulation, flocculation, and dissolved air flotation (DAF) experiments were performed with humic acid to evaluate the influence of operational conditions on removal efficiencies. We investigated coagulation, flocculation, and flotation conditions of humic acid removal using a laboratory-scale DAF system. This paper deals with coagulant type (aluminum sulfate and PSO-M) and the most relevant operational conditions (velocity gradients for coagulation and flocculation, retention time and recycle ratio and flotation time). Results showed that optimal conditions for removing humic acid, yielding CHA removal efficiencies of approximately 85 %, are a recycle ratio of 40 %, coagulant dosages of 0.15 - 0.20 gAl/gHA as aluminum sulfate and 0.03 - 0.12 gAl/gHA as PSO-M, coagulation($400s^{-1}$ and 60s), flocculation($60s^{-1}$ and 900s or more), and flotation(490 kPa or more and at least 10 min).

• Particle and aerosol research
• /
• v.4 no.2
• /
• pp.69-75
• /
• 2008

Nanosize ZnO particles were prepared by oxidation of zinc vapor and the particle growth was modeled by a coagulation model by assuming that the characteristic time for reaction was much shorter than coagulation time and residence time (${\tau}_{reaction}{\ll}{\tau}_{coagulation}{\ll}{\tau}_{residence}$). Experimental measurement of zinc oxide particles diameter was consistent with the predicted result from the coagulation model. For practical purpose of predicting zinc oxide size in areosol reactor, the constant kernel solution is concluded to be sufficient, Uniqueness of nano-scale property of zinc oxide was confirmed by the higher photocatalytic activity of zinc oxide than nanosize titania particles.

• Proceedings of the Korean Environmental Sciences Society Conference
• /
• 2003.11b
• /
• pp.319-321
• /
• 2003

This research was carried out to evaluate the removal efficiencies of CODcr and colour for the dyeing wastewater by ferrous solution in Fenton process. The results showed that COD was mainly removed by Fenton coagulation, where the ferric ions are formed in the initial step of Fenton reaction. On the other hand colour was removed by Fenton oxidation rather than Fenton coagulation. The removal mechanism of CODcr and colour was mainly coagulation by ferrous ion, ferric ion and Fenton oxidation. The removal efficiencies were dependent on the ferric ion amount at the beginning of the reaction. However the final removal efficiency of COD and colour was in the order of Fenton oxidation, ferric ion coagulation and ferrous ion coagulation. The reason of the highest removal efficiency by Fenton oxidation can be explained by the chain reactions with ferrous solution, ferric ion and hydrogen peroxide.

• Journal of Korean Society of Water and Wastewater
• /
• v.23 no.4
• /
• pp.459-469
• /
• 2009

It is well known that coagulation pretreatment can reduce foulants prior to membrane filtration. The purpose of this research was to investigate the effects of coagulation on fouling of ceramic microfiltration membrane($0.1 {\mu}m$) using pilot plant of $150m^3/day/train$ capacity. Train A membrane system has pretreatment process of ozonation and coagulation while train B has only coagulation. Two types of coagulation operation were investigated: back mixer(rapid mixing with or without slow mixing) which is a conventional mechanically stirred mixer and an inline static mixer. Ozone dose rate for train A was 1 mg/L and ozone contact time was 12 min. The coagulation dose(PACl 10% as $Al_2O_3$) rate was changed 20~40 mg/L according to experimental schedule. In this experimental conditions, the coagulation of back mixer type with rapid mixing(GT=72,000) and slow mixing(GT=45,000) was the best effective in reduction of ceramic membrane fouling regardless preozonation. Especially, the effect of inline static mixer was sensitive to change in water quality. Ozonation mainly affected irreversible fouling rather than reversible fouling in accordance with less adsorption of NOM on the membrane surface. Thus, the increase rate of the nomalized TMP(trans membrane pressure) at $25^{\circ}C$ for train A was relatively lower than that of train B under same coagulation process with same coagulant dosage. The best performance of ceramic membrane appeared in case of combined process with ozonation, therefore this integrated process is able to archive less coagulant dosing and secure a stability of ceramic membrane system.