No abstract

This study aimed to enhance boron removal through powdered activated carbon adsorption (PAC) and application of a micro-filtration (MF) process as a pretreatment of a seawater reverse osmosis (SWRO) process. Batch and continuous experiments were conducted to investigate the effect of membrane filtration as well as PAC addition on boron removal in reconstituted seawater. In batch test, two kinds of polyvinylidene fluoride (PVDF) hollow fiber membrane, Module A and Module B, were used to assess the influence of pH and PAC on boron removal, whereas in continuous mode, two MF systems with submerged PVDF flat-sheet membrane were run in parallel. Modules A and B obtained the highest percentage boron removal at pH 9 in the batch experiment with an average value of 47.33%, and their concentration of boron was further reduced after addition of PAC increasing the removal to 51.33 and 69.33%, respectively. For the continuous operation, PAC addition decreased the boron concentration by 20–30 and 40% in the reactor and effluent, respectively. On the other hand, only 5% reduction was obtained inside the reactor and 30–40% in the effluent for the system without PAC. Thus, operating the system at high pH with PAC addition could enhance the performance of the adsorption-MF system, which can be used as a pretreatment for the SWRO process.

Sulfur-based carriers were examined to enhance the nitrogen removal efficiency in a mixed anoxic–anaerobic-membrane bioreactor system, in which sulfur from the carrier acts as an electron donor for the conversion of nitrate to nitrogen gas through the autotrophic denitrification process. A total nitrogen removal efficiency of 63% was observed in the system with carriers, which showed an increase in the removal efficiency of around 20%, compared to the system without carriers. The results also indicated that the carriers had no adverse effect on biological treatment for the organic matter and total phosphorus. The removal efficiencies for chemical oxygen demand (COD) and total phosphorus (TP) were 98% and 37% in both systems, respectively. The generation of sulfate ions was a major disadvantage of using sulfur-based carriers, and resulted in pH drop. The ratio of sulfate in the effluent to nitrate removed in the system ranged from 0.86 to 1.97 mgSO42−/mgNO3−-N, which was lower than the theoretical value and could be regarded as due to the occurrence of simultaneous heterotrophic and autotrophic denitrification.

Various kinds of micro organic pollutants have frequently been detected from a water system. Therefore, it is considered to be very important part in the drinking water treatment system. And the research about removal process and processing efficiency have been being conducted briskly. In this study, the removal efficiency was evaluated using advanced water treatment process and nanofiltration process. The removal efficiency of nanofiltration process was very different according to physical and chemical characteristics of materials. The molecular weight of cutoff was the most influential factor in the removal efficiency. And when pKa value was higher than pH of raw water or Log Kow value was below 2, the removal efficiency of material was decreased. In case of oxidation reaction, the bigger the molecular weight of material was and the more hydrophobic a material was, the less oxidation reaction occurred. And the removal efficiency was decreased. Most unoxidized materials were removed by absorption. And the more actively oxidation reaction occurred by H2O2, the more absorption reaction increased. 요약 : 수계에서 검출되는 미량유해물질의 빈도와 종류가 다양해지고 있다. 따라서 정수처리시스템에서 고려되어야 할 부분 으로 거론되고 있으며 제거공정과 처리효율에 대한 연구가 활발하게 진행되고 있다. 본 연구에서는 고도처리공정과 나노여 과공정을 이용한 제거효율을 평가하였다. 나노여과공정의 경우 물질의 물리화학적 특성에 따라 제거율이 상이하게 나타났 다. 물질의 분획분자량이 제거율이 가장 큰 영향을 미치는 것으로 확인되었다. 또한, 원수의 pH보다 높은 pKa 값을 갖거나 Log Kow 값이 2 이하인 물질의 제거효율이 감소되었다. 고도처리공정 중 산화공정에서는 대상물질의 분자량이 클수록 그리 고 소수성을 띌수록 산화반응에 의한 제거효율이 감소되었다. 흡착공정에서는 산화되지 않은 대부분의 물질이 제거되었으며 H2O2에 의하여 산화가 더 잘 진행될수록 흡착반응이 향상되었다. 주제어 : 고도처리, 나노여과, 미량유해물질, 오존, 입상활성탄 1. 서 론 급속하게 진행 중인 도시화와 산업화에 따라 상수원으로 유입되는 유해 오염물질들이 다양화되고 그 양도 증가하고 있는 추세이다. 전 세계적으로 취수원수로 사용되고 있는 지표수 중에서 내분비계교란물질(endocrine disrupting compounds, EDCs), 의약물질(pharmaceuticals and personal care products, PhACs), 신규우려물질(contaminants of emerging concerns, CECs), 개인관리용품(personal care products, PCPs) 과 같은 미량유해물질의 검출이 보고되고 있으며 물질에 대한 규제 또한 강화되는 추세이다. 미량유해물질은 ug/L, ng/L 단위의 미량으로도 인체에 위해를 가할 수 있는 물질 로 차세대 정수처리 시스템에서 반드시 고려되어야 할 부 분들이다. 응집/침전/모래여과와 같은 기존 정수처리공정, 오존/활성탄과 같은 고도처리시스템 및 막여과 공정(정밀 여과/한외여과)에서의 제거율 및 제거 메카니즘에 조사가 필 요한 실정이다. 농약류, 합성세제, 색도 유발물질, 의약물질 및 내분비계 장애물질 등의 난분해성 오염물질은 염소나 오존을 이용해 서 효과적으로 산화 제거하기에는 한계가 있으며 1,2) 산화효 율 증진을 위해 과다한 염소의 투입은 트리할로메탄과 같 은 소독부산물을 과다하게 생성시키며 과다한 오존투입의 경우도 비경제적이다. 또한, 의약물질은 특정한 생리작용을 유지하기 위해 물에 잘 용해되지만 생분해가 잘 일어나지 않고 화학적으로 안정적이기 때문에 기존의 정수처리공정 만으로는 제거하기가 힘들다. 다양한 물리화학적 성질을 가 지는 의약물질들을 원수에 주입한 후 응집과 활성탄 흡착, 오존처리를 통해서 제거를 하였을 경우, 응집과 활성탄 흡 착으로는 산성의약물질들의 제거율이 현저히 낮고 오존에 의해서도 일부 의약물질은 분해가 잘되지 않는 것으로 보 고된 바 있다. 3,4) 일반적으로 나노여과 공정에서 미량유해물질의 제거효율 은 M.W (Molecular weight), log Kow, Dipole moment, Structure 등에 따라 다르게 나타난다. 분자량이 큰 것이 일 반적으로 제거효율이 증가되지만 결합된 구조에 따라 제거 효율이 다르게 나타날 수 있다. 또한, 물질이 소수성을 띌수

To cite this article: Ramon Christian Eusebio , Joon-Seok Kang & Han-Seung Kim (2011) Application of integrated microfiltration and PAC adsorption for the removal of humic acid as a pretreatment in seawater desalination, Desalination and Water Treatment, 34:1-3, 81-87To link to this article: http://dx. A B S T R AC TThis study evaluated the effectiveness of powdered activated carbon (PAC) in removing organic matter under saline condition with the application of microfi ltration (MF). Adsorption isotherm test was conducted to compare the adsorptive potential of humic acid (HA) on PAC between reconstituted seawater and aqueous solution. Subsequently, two MF systems were run in parallel to investigate the effect of PAC and fi ltration process on HA removal. Various parameters such as turbidity, SDI 15 , UV 254 , dissolved organic carbon and transmembrane pressure were monitored within one-month operation. The batch experiment results showed that an increase in PAC concentration enhanced the adsorption potential of HA on activated carbon. Same trend was observed in the continuous experiment conducted with microfi ltration. Percent removal of organics reached 60% for the control system while 90% for MF-PAC system. Lower SDI 15 and turbidity values were obtained in the system with PAC. Adsorptive capacity of PAC with organic matter was higher in saline solution due to the ionic strength exhibited by salts present in seawater, and removal of humic acid in seawater was increased by the addition of activated carbon. Consequently, membrane fi ltration coupled with adsorption enhanced the removal of organic matter in reconstituted seawater producing better quality of effl uent water.