• Journal of the Korean Society for Environmental Technology
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• v.19 no.6
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• pp.570-575
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• 2018

The various of raw wastewater inflows to the industrial wastewater treatment plants everyday. This makes it difficult to operate the coagulation and flocculation efficiently as a pretreatment process for the industrial wastewater treatment. Additionally, it causes loads on evaporation and membrane facilities which are the posttreatment and alternative processes. For this reason, this study sampled raw wastewater before and after the NaOH injection. An experiment was conducted to compare the coagulation characteristics according to the methods of coagulant injection (single injection, simultaneous injection, consecutive injection, and inverse injection) aiming at efficient treatment of industrial wastewater. The coagulation experiment was conducted using a jar tester. The TDS removal efficiency by the coagulant injection methods increased in the order of consecutive injection (2.8 %) < single injection (3.9 %) < simultaneous injection(8.1 %) < inverse injection(9.6 %); the TOC removal efficiency grew in the order of single injection (84.3 %) < inverse injection (86.2 %) < consecutive injection (88.6 %) < simultaneous injection (89.1 %); the turbidity removal efficiency grew from single injection (99.7 %) < consecutive injection (99.8 %) ${\fallingdotseq}$ inverse injection (99.8 %) < simultaneous injection (99.9 %). These results show that the simultaneous inorganic coagulant-polymer coagulant injection method was more efficient than the consecutive injection method (inorganic coagulant ${\rightarrow}$ polymer coagulant).

• Clean Technology
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• v.8 no.2
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• pp.85-92
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• 2002

Red mud is generated as a by-product during the production of aluminum hydroxide from bauxite ore. In this study the red mud coagulants were prepared by reacting 100 ml of 5 M $H_2SO_4$ solution with 10g of red mud at $85^{\circ}C$ or by reacting 100ml of 9M HCl solution with 10g of red mud at $25^{\circ}C$. The prepared red mud coagulants were tested for their coagulation performance of pollutants in the municipal and industrial wastewater. In addition, the coagulation performance was compared with that of a commercially available coagulant ($FeCl_3$). As a result, the red mud coagulants were found to have a good removal efficiency of pollutants in the municipal wastewater (turbidity, phosphate phosphorus) and in the plating wastewater (turbidity, $Pb^{2+}$, $Cd^{2+}$, $Cu^{2+}$, $Zn^{2+}$, $Cr^{3+}$). In the experiment to remove COD in the petrochemical wastewater, the COD removal efficiency by the red mud coagulants was a little poor, but it was better than that by $FeCl_3$.

• KSBB Journal
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• v.10 no.4
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• pp.421-427
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• 1995

A fungal strain, designated Aspevgillus sp. JS-42, was isolated and shown to produce an extracellular polysaccharide used as a bioflocsulant. The optimal medium composition for the production of flocculant with Aspergillus sp. JS-42 was glucose 3.0%, yeast extract 0.2%, $(NH_4)_2S0_4 0.1%, CaCI_2.2H_2 0.05%$ in distilled water. The optimum culture temperature and optimum culture pH for the production of the flocculant were $25^{\circ}C$ and pH 7.0, respectively. The highest production of flocculant was observed after 90 hours of cultivation at the optimal condition. The flocculant could efficiently flocculaled the tested solids suspended in aqueous solution and was stable at high temperature($100^{\circ}C$) and to pH range of from 2 to 10. The flocculant seems to be a kind of high viscous polysaccharide.

• Polymer(Korea)
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• v.37 no.3
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• pp.342-346
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• 2013

In this study, it was attempted to disperse carbon nanotubes (CNTs) in a polymer matrix using a twin-screw extruder which was good for dispersing fillers of micron sizes but not suitable for dispersing nanometer-sized materials. Improved dispersion of CNTs could be achieved by the addition of inorganic fillers with different geometrical shapes. An increase in the matrix viscosity provided a high shear stress on aggregated CNTs, leading to a good dispersion of CNTs. The presence of the inorganic fillers was supposed to suppress the re-aggregation of CNTs in the regions where a lower shear stress was applied. As a result, the CNTs dispersion was well stabilized.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.859-863
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• 2008

축산폐수, 침출수 등의 고농도 폐수를 생물학적으로 처리할 경우 최종 방류수는 강한 색도를 띠며 고분자량의 유기물질을 다량 함유한다. 이는 생물학적으로 분해하기 어려운 유기성 복합체와 생화학적 반응에 의한 중간생성물로 색도를 띠는 천연유기물질(NOM)을 포함한다. 생물학적 처리수의 색도는 심미적인 불안감, 방류수역의 수질오염 및 공중보건상의 잠재적 위해성을 갖는다. 또한, 수자원 이용측면에서 정수처리공정에서의 약품투입량 증가와 특히, 소독부산물 생성이라는 잠재적 문제점이 뒤따른다. 따라서 이러한 문제점을 해소하기 위한 생물학적 2차 처리수의 후속처리가 요구되며, 실제로 난분해성 유기물과 색도를 제거하기 위한 흡착, 막 분리, 고급산화(AOP) 및 화학적 응집 등의 물리-화학적 공정에 대한 연구가 수행되어왔다. 특히, 화학적 응집은 무기응집제 또는 고분자중합체(Polymer)를 이용하여 콜로이드성 입자와 색도를 띠는 난분해성 유기물을 전기적 불안정화를 유도함으로서 흡착 및 응집과정을 통해 제거하는 공정으로 많은 연구자들에 의해 연구되어왔다. 그러나 난분해성 유기물과 색도제거는 대상원수의 성상과 화학적 특성 등에 따라 각각의 제거효율과 최적 운전조건이 상이하게 나타난다. 화학적 응집공정은 비교적 높은 제거효율을 보이지만, 운전 및 유지관리의 기술적 어려움, 경제적 비효율성 등으로 인하여 적용에 어려움을 겪고 있는 실정이다. 본 논문에서는 생물학적 혐기-호기성 공정에서 방류되는 축산폐수의 2차 처리수를 대상으로 화학적 응집에 의한 색도 및 난분해성 유기물의 제거거동을 고찰하였다. 대상 처리수의 $TCOD_{Cr}$ 농도는 평균 410 mg/L인 반면, $BOD_5$는 7-15 mg/L 범위로 난분해성 유기물을 다량 함유하고 있음을 알 수 있었다. 이에 황산알루미늄(Aluminium sulfate; $Al_2(SO_4){\cdot}14H_2O$)과 염화철(ferric chloride)의 무기응집제를 이용하여 자 테스트(jar test)를 수행한 결과, 동일한 응집제 주입량에서 염화철의 유기물 제거 효율이 높은 것으로 나타났다. 황산알루미늄과 염화철의 경우 각각의 응집제 주입율 5.85mM에서 89%, 7.03mM에서 97.5%의 최대 유기물 제거효율을 보여주었으며, 이 때 최종 pH는 4.0-5.6 범위이었다. 한편, 대상 원수 내의 콜로이드성 입자 또는 용존성 유기물의 작용기(functional group)는 일반적으로 음으로 하전 되어 있어 응집에 의해 잘 제거되지 않는 특성을 가지고 있다. 따라서 과량의 응집제를 주입하여 다가의 양이온성 금속염을 흡착시켜 전기적으로 중화시키고, 생성된 침전성 수화물 내에 포획 또는 여과시켜 제거하게 된다. 이 때, 금속염 수화종의 전하밀도가 응집효율에 영향을 주는 것으로 알려져 있는데, 다가의 양이온은 전기적 이중층(Double layer) 압축에 의한 불안정화를 향상시킬 수 있기 때문에다. 또한, 2가 금속염은 색도유발물질과 흡착하여 humate 또는 fulvate 등의 착화합물(complex)을 형성시켜 응집효율을 향상시킬 수 있다. 따라서 본 연구에서는 생물학적 2차 처리수의 화학적 응집처리에 있어서 알루미늄염 등의 다가이온 첨가가 응집에 미치는 영향을 관찰하고, 후속되는 플록형성 및 침전공정에 의한 제거효율을 비교, 평가함으로써 2차 처리수로부터 난분해성 유기물과 색도를 보다 효과적이고 경제적으로 제거할 수 있는 최적인자를 도출하고자 하였다.

• Clean Technology
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• v.11 no.2
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• pp.57-67
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• 2005

Epoxy resins are produced by the dehydro condensated reaction with ECH (Epichlorohydrin) and BPA(Bisphenol-A) as raw reactants under sodium hydroxide(NaOH) as a catalyst, and from this reaction, salted water named of brine, which contains ECH derivatives in condition of emulsion as likely as glycidol and polymer resins, is produced as an undesired side product. This brine water is alkaline wastewater and causes process fouling problems by plugging and chemically depositing polymer particles on the surface of inner wall of reactors and pipes, and decreases the biodegradable efficiency in the wastewater process. In this study, the optimization of coagulation and sediment reactions, using inorganic and organic polymer coagulants, were performed to remove the causes occurring the process fouling phenomena. And also, based on this study, the methodologies applicable to the commercial processes including economical analysis were presented.

• Journal of the Korean Chemical Society
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• v.48 no.3
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• pp.273-282
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• 2004

The synthetic technology of improved polyaluminiumchloride (IPAC) similar to characteristics of PACS was established with minimum expense for modifying existing production line. The conditions for activating silicate was studied before the synthesis of IPAC, and the IPAC was synthesised with raw materials such as aluminumhydroxide and concentrated hydrochloric acid, followed by adding activated silicate and alginate. The specification of product, chemical structure, and coagulating properties were tested by using specification testing method, instrumental analytical method, and Jar tester, respectively. As a result, the product, IPAC, contained aluminium oxide content more than 17%, and no precipitation was shown at all while the IPAC solution was preserved, and the larger floc and faster coagulation were represented compared to existing PAC under the same conditions. It was suggested that these synthetic technology could be applied to the existing production line for producing PAC without approximately cost raising factor because of adding sulfuric acid-activated silicate instead of sodium sulfate.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.279-289
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• 2000

The objective of this study was to investigate the effect of coagulants and solid-liquid separation methods on algal removal in water treatment processes. Thus characterization of raw water quality in terms of turbidity. UV-254, $KMnO_4$ consumption, chlorophyll-a and correlation analysis of these parameters were conducted. In addition, the effect of commercial Al-based coagulants(Alum. PAC and PACS) on algal removal was studied by turbidity and organic removal, algal species removal, characteristic of pH drop and alkalinity consumption using laboratory jar tests. Organic components including UV-254, $KMnO_4$ consumption, chlorophyll-a in case of algal bloom were highly correlated with turbidity and the correlation coefficients of UV-254, $KMnO_4$ consumption, chlorophyll-a with turbidity were 0.775, 0674 and 0.623, respectively. In coagulation and sedimentation, the Al-based coagulants showed similar efficiency of organic and turbidity removal in low organic($KMnO_4$ consumption below 15mg/l) and low turbidity(below 30NTU). However, PAC and PACS showed better algal removal than alum in high organic concentration($KMnO_4$ consumption above 20mg/l) and high turbidity(above 100NTU) raw water conditions generated by high algal growth, which is considered to be due to the floc settleability. In comparison of sedimentation and flotation after chemical coagulation and flocculation, the removal efficiency of organic and turbidity were higher in case of alum dose with flotation than with sedimentation, while those were better in case or PAC and PACS with sedimentation than with flotation. Thus, Alum with flotation and PAC and PACS with sedimentation is recommended for efficient algal removal. The dominant phytoplankton in raw water were Microcystic and pediastrum simplex and the removal efficiency of algae with sedimentation using alum. PAC and PACS were 27%, 45% and 22% respectively, while those with DAF showed 100% removal of phytoplankton and zooplankton.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.588-597
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• 2004

In this research, we investigated the variation of transmembrane pressure and permeate water quality with pre coagulation and sedimentation with iron based coagulant and chlorination of feed water for PVDF (polyvinylidene fluoride) based MF membrane filtration. NaCIO was fed to the membrane module with dosage of 0.5mg/L and maintained during filtration. To observe the effect of raw water, three types of raw and processed waters, including river surface water, coagulated water and coagulated-settled water, were applied. In case of river surface water, the transmembrane pressure increased drastically in 500 hours of operation. On the contrary, no significant increase in transmembrane pressure was observed for 1,200 hours of operation for coagulated water and coagulated-settled waters. The turbidity of permeate was lower than a detection limit of equipment for all raw waters. The removal efficiency of humic substances of coagulated water and coagulated-settled water was approximate ten times of that of surface river water. And, the removal efficiency of TOC and DOC was approximate two times of that of surface river water. From the results of plant operation, stable operation was maintained at $0.9m^3/m^2{\cdot}day$ filtration flux through the combination of pre-coagulation and pre-chlorination. However, the water quality of permeate was the best when pre-coagulation-sedimentation process was combined with pre-chlorination.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.7
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• pp.683-687
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• 2008

When suspended solids are removed by natural sedimentation, it is necessary to use mainly huge equipments and waste great cost. This is a problem that must be solved certainly as soon as possible. In this study, suspended solids of yellow soil water were rapidly removed by controlling pH and amounts of magnetic powder, organic and inorganic flocculants. In the case of the suspended solids of 0.3% yellow soil water, the most excellent turbidity was achieved at pH between 7 and 7.5.