Journal of Environmental Impact Assessment (환경영향평가)

Korean Society of Environmental Impact Assessment (한국환경영향평가학회)
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Treatability Study on the Remediation Groundwater Contaminated by TPH Cr6+ : Lab-Scale Experiment

TPH와 6가 크롬으로 오염된 지하수 처리를 위한 실내 실험

  • Lee, Gyu-Beom (Department of Environmental Engineering, Kwangwoon University) ;
  • Chang, Yoon-Young (Department of Environmental Engineering, Kwangwoon University)
  • Received : 2019.05.22
  • Accepted : 2019.06.07
  • Published : 2019.06.30
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Abstract

The purpose of the study is to evaluate the treatability of contaminated groundwater with TPH and (or) $Cr^{6+}$. Laboratory scale tests were performed for oil/water separation, dissolved air flotation (DAF), coagulation and precipitation, and filtration with sand and activated carbon respectively. Two times of oil/water separation tests for total 40 minutes of separation or separating time shows 90.2 % of TPH removal rate. In case of DAF test for high TPH sample, the TPH removal rates were not varied significantly by the variation of microbubble size. However, tests for low TPH samples show that TPH removal rate increases as microbubbles are smaller. When coagulant was added to sample for DAF test, TPH removal rate was increased 12.3 %. SS removal rate by DAF was 97.9 % at $16-40{\mu}m$ and it was increased as the size of microbubble is reduced. Tests for coagulation and precipitation were performed to evaluate the removal of $Cr^{6+}$ in groundwater. The increase of $FeSO_4$ dosage increased $Cr^{6+}$ removal rate in the coagulation and precipitation process. As the amount of activated carbon in the filter media increased TPH removal rate in the filtration process. SS removal rate by the filtration was 96.7 % similar to the results of DAF process tests. The filtration process treats TPH and SS. Best design parameters are determined as the size of sand is $425-850{\mu}m$ and the ratio of activated carbon and sand is 50:50.

이 연구의 목적은 TPH 또는 $Cr^{6+}$이 함유된 오염 지하수의 처리 가능성을 평가하는 데 있다. 오일과 물의 분리, 용존 공기 부유 (DAF), 응고 및 침전, 모래와 활성탄으로 각각 여과를 위한 실험실 규모 테스트가 수행되었다. 총 40 분간의 분리 시간 동안 오일과 물의 분리 시험을 2 회 실시한 결과 TPH 제거율은 90.2 %였다. 높은 농도의 TPH 샘플에 대한 DAF 테스트의 경우, TPH 제거율은 미세 기포 크기의 변화에 따라 크게 변하지 않았다. 그러나 낮은 TPH 샘플에 대한 테스트는 미세 기포가 작을수록 TPH 제거율이 증가함을 보여준다. DAF 테스트를 위해 응집제를 샘플에 첨가했을 때 TPH 제거율은 12.3 % 증가했다. DAF에 의한 SS 제거율은 $16{\sim}40{\mu}m$에서 97.9 %였으며 미세 기포의 크기가 감소함에 따라 증가했다. 지하수에서 $Cr^{6+}$의 제거를 평가하기 위해 응집 및 침전 시험을 수행했다. $FeSO_4$ 투여량을 증가하였을때 응집 및 침전 공정에서 $Cr^{6+}$ 제거율이 증가하였다. 필터 매체에서 활성탄의 비율이 높을수록 여과공정에서 TPH 제거율이 증가한다. 여과에 의한 SS 제거율은 DAF 공정 시험 결과와 비슷한 96.7 %였다. 여과 과정은 TPH와 SS 농도가 감소하였다. 모래의 크기가 $425{\sim}850{\mu}m$이고 활성탄과 모래의 비율이 50:50일때 최적의 처리효율을 나타냈다.

Keywords

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Figure 1. Proposed flow diagram of ground water treatment facility.

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Figure 2. Methods of laboratory tests.

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Figure 3. TPH removal results of oil water separation tests.

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Figure 4. TPH removal results of dissolved air floater tests according to microbubble sizes. (a), (b), (c) initial TPH concentration 751.33 mg/L, (d), (e), (f) initial TPH concentration 132.84 mg/L.

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Figure 5. TPH removal results of dissolved air floator tests with (a) coagulant (Al2(SO4)3)microbubble size 16$\boxtimes$40 μm), (b) coagulant (Al2(SO4)3) and powdered activated carbon (PAC).

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Figure 6. TPH removal results of filtration tests.

Table 1. Evaluation parameters of selected treatment processes

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Table 2. Chemical properties of contaminated groundwater.

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Table 3. SS removal results of dissolved air floator tests according to micro-bubble sizes

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Table 4. Cr6+ removal efficiency (%) of coagulation and sedimentation tests according to the amount of Al2(SO4)3 and FeSO4

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Table 5. SS removal results of filtration tests

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Table 6. Cr6+ removal results of filtration tests

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