Abstract
In this study, the solid-liquid separation characteristics of swine wastewater were investigated for the coagulation and dissolved air flotation (DAF). Coagulation characteristics were studied using jar-tester with the different coagulants and dosage amounts. DAF characteristics were also investigated in terms of the different flotation conditions with the raw swine wastewater, pH adjustment only, and adding coagulants. When the raw swine wastewater was coagulated with the only inorganic coagulants, the proper inorganic coagulants were founded as $FeCl_3$ > PAC > Alum orderly, and the optimal coagulant dosages were founded as $1,000mg/{\ell}$, $1,500mg/{\ell}$, $1,500mg/{\ell}$, respectively. As the raw swine wastewater was treated with the polymer coagulants, the only cationic polymer coagulant showed an effective coagulation and the optimal dosage of cationic coagulant was founded as $200mg/{\ell}$. When the different dosages of cationic polymer was added to each $500mg/{\ell}$ of the inorganic coagulants, the proper inorganic coagulants were founded as $FeCl_3$ > Alum > PAC orderly, and optimal cationic polymer dosages was founded as $25mg/{\ell}$, $25mg/{\ell}$, and $100mg/{\ell}$, respectively. Resulting from the raw swine wastewater experiments using DAF without coagulation, the proper operation conditions of DAF were set to 400% of recycling ratio, 4 atm in air dissolving tank, and under pH 3. But the raw swine wastewater was difficult to successfully operate DAF without pre-coagulation. While the DAF separation after pre-coagulation using inorganic coagulants was not accomplished due to the low intensity of the floc, DAF after pre-coagulation using both the inorganic and cationic polymer coagulants was accomplished very well. Optimal dosage of cationic polymer coagulant in case of $500mg/{\ell}$ Alum dosage was founded as $500mg/{\ell}$.
본 연구는 응집 및 부상분리를 이용하여 돈사폐수의 고액분리 특성을 조사하였다. 응집은 jar-tester를 이용하여 응집제 종류 및 주입량에 대해, DAF를 이용한 부상분리에서는 돈사폐수 원수 자체에 대한 부상조건과 pH만을 조정한 원수, 그리고 응집제를 주입한 후 부상을 통한 고액분리 특성을 실험적으로 연구하였다. 돈사폐수를 무기응집제 만으로 응집침전 처리하는 경우 $FeCl_3$ > PAC > Alum 순으로 응집침전효과가 나타났으며, 적정 응집제 주입량은 각각 $1,000mg/{\ell}$, $1,500mg/{\ell}$, $1,500mg/{\ell}$으로 나타났다. 고분자응집제 만으로 응집침전 처리하는 경우 양이온 응집제만이 유효한 응집침전 효과가 나타났으며 적정 응집제 주입량은 $200mg/{\ell}$로 나타났다. 무기응집제와 고분자응집제를 혼합 적용한 경우 각 무기응집제를 $500mg/{\ell}$ 투여한 후 양이온 고분자응집제 주입 농도를 달리하여 응집침전효과를 고찰한 결과 무기응집제의 처리 효율은 $FeCl_3$ > Alum > PAC순으로 나타났으며, 적정 양이온 응집제 주입농도는 $25mg/{\ell}$, $25mg/{\ell}$, $100mg/{\ell}$로 나타났다. DAF를 이용한 부상분리 실험에서 응집처리를 하지 않은 원수와 pH만을 조정한 원수에서의 실험결과를 종합하여 순환비 400%, 압력 4 atm, pH 3이하에서 DAF의 적정 운전 조건이 나타남을 알 수 있었다. 그러나 응집처리를 하지 않은 돈사폐수 원수를 대상으로 DAF를 적정하게 운전하기는 곤란한 것으로 판단되었으며, 또한 무기응집제로만 응집처리한 후 부상분리를 실시하였을 경우 floc의 강도가 약해 floc의 깨짐 현상이 나타나 부상분리가 이루어지지 않았다. 한편 무기응집제와 고분자응집제를 혼합하여 응집처리한 후 부상분리를 실시하는 경우 효과적인 부상분리가 이루어졌으며, Alum $500mg/{\ell}$를 기준으로 양이온 고분자응집제 주입농도가 $50mg/{\ell}$에서 가장 양호한 처리 결과를 나타내었다.