하수 응집처리 시 플록 특성 및 인 제거율 변화

국문 초록 (Abstract)

본 연구에서는 하·폐수 처리 공정에서 핵심 관리 항목인 총인(T-P) 제거공정의 안정성을 향상시키기 위해, 응집제 종류(PAC, Alum, FeCl₃,Polymer) 및 주입농도 변화가 플록 형성 특성과 침전성능(SVI)에 미치는 영향을 정량적으로 분석하였다. 또한 수온 변화(13°C, 18°C, 23°C)가 응집반응 및 플록 성장 메커니즘에 미치는 영향을 평가하여 계절 변화에 따른 최적 응집 조건을 제시하였다. 먼저, 초기 원수는 50 μm 미만의 미세입자가 높은 비율을 차지하는 분산형 입도 특성을 보였으며, 이는 응집 초기 플록 성장 속도를 제한하는 주요 요인으로 작용하였다. 응집제 주입농도(10–60 mg/L)를 단계적으로 증가시키며 측정한 결과, PAC·Alum·FeCl₃는 20–30 mg/L 구간에서 D50과 제거효율이 동시에 크게 향상되어 최적 농도로 확인되었다. 반면 Polymer 응집제는 금속염과 달리 전하중화보다는 bridging 효과를 통해 플록을 형성하여, 동일 농도 기준에서 상대적으로 작은 입경(D50)과 낮은 제거효율을 나타냈다. 플록 크기(D10, D50, D90)와 SVI 간의 상관성을 분석한 결과, D50 증가에 따라 SVI가 감소하는 공통적 패턴을 확인하였다. 그러나 과량 주입 시에는 charge reversal 및 플록 내부 구조의 불균질화로 인해 플록이 재분산되고 Span 값이 증가하여 SVI가 다시 상승하는 비선형적 반응이나타났다. 특히 Span–SVI 분석에서 Span 1.6–2.2 범위일 때 가장 안정적인 침전성을 확보할 수 있으며, Span ≥ 3.0에서는 불안정한 플록 구조로 인해 침전성이 저하되는 특성이 확인되었다. 수온 변화 실험에서, 18°C 조건에서 플록 성장(D50), 입경 분포(Span), SVI가 가장 안정적으로 나타났으며 응집반응이 최적으로 수행되는 온도로 판단되었다. 저수온(13°C)에서는 가수분해 속도 저하로 인해 플록 크기 증가가 제한되며 SVI가 증가하였고, 고수온(23°C)에서는 급격한 가수분해 및 부분 재분산으로 Span이 증가하여 침전성이 다소 저하되는 경향을 보였다. 종합하면, 응집제별 주입농도와 수온 변화는 플록 구조와 침전성능에 상호 영향을 미치며, 최적 응집 조건은 PAC·Alum·FeCl₃ 기준 20–30 mg/L, 수온 18°C로 확인되었다. 본 연구 결과는 하수처리시설에서 응집제 주입전략을 최적화하고 계절 변동에 대응한 안정적 공정 운영을 위한 기초자료로 활용될 수 있다.

목차 (Table of Contents)

• 제 1 장 서 론 ···································································································1
• 1.1 연구 배경 ·············································································································1
• 1.2 연구 목적 ·············································································································4
• 제 2 장 연구 재료 및 방법 ··········································································5
• 2.1 연구 재료 ·············································································································5
• 2.1.1 원수 성상 ··································································································5
• 2.1.2 응집제 종류 및 특성 ··············································································7
• 2.2 연구 방법 ·············································································································8
• 2.2.1 응집제 주입농도별 수질 및 플록 크기 측정 ····································8
• 2.2.2 플록 특성에 따른 SVI 기반 침전성능 평가 ·····································9
• 2.2.3 수온·원수 성상 변화 실험 ··································································10
• 제 3 장 결과 및 고찰 ··················································································11
• 3.1 원수 및 플록 특성 분석 ·················································································11
• 3.1.1 원수 특성 및 채수 조건 ·······································································11
• 3.1.2 초기 플록 입도 특성 분석 ···································································12
• 3.2 응집제 주입농도에 따른 수질·플록 크기 변화 평가 ······························14
• 3.2.1 응집제 농도별 인 제거율 ·····································································14
• 3.2.2 주입농도별 플록 입도분포 변화 ·························································17
• 3.2.3 주입농도별 침전성능(SVI) 변화 ·························································19
• 3.3 플록 크기와 침전성능(SVI)의 상관 분석 ·················································21
• 3.3.1 플록 입경과 SVI의 상관성 ··································································21
• 3.3.2 플록 성장·응집도와 침전성능의 정량적 관계 ································· 25
• 3.4 수온 및 원수 성상 변화에 따른 응집 특성 평가 ··································· 26
• 3.4.1 수온 변화가 응집·플록 특성에 미치는 영향 ··································· 26
• 3.4.2 수온 변화에 따른 SVI 및 침전성능 변화 ········································29
• 제 4 장 결론 ··································································································31
• [참고문헌] ·········································································································33