The ballasted flocculation effects of the mill scale and magnetite on activated sludge were investigated. Both ballasted flocculants (BF) could remarkably improve the sludge settleability in terms of zone settling velocity (ZSV) and sludge volume index (SVI). With the BF dosage of 0.2 to 2.0 g-BF/g-SS, the magnetite particles showed better efficiency on improving settling behavior of activated sludge than the mill scale due to higher surface area and hydrophobic property. The efficiency of SVI30 with magnetite injection was 2.5 to 11.3% higher than mill scale injection and that of the ZSV appreciated from 23.7% to 44.4% for magnetite injection. Averaged floc size of the BF sludge with magnetite dosage (0.5 g-BF/g-SS) was 2.3 times higher than that of the control sludge. Dewaterability of the sludge was also greatly improved by addition of the BF. The specific resistance to filtration (SRF) was reduced exponentially with increasing the dosage of BF. However, the BF’s particle size effect on the SRF looks to be marginal. Consequently, for improving the dewaterability, the BF played a physical role to remove the pore water of the biological flocs by intrusive attachment and a chemical role to induce aggregation of the flocs by charge neutralization.

ABSTRACT
1. 서 론
2. 재료 및 실험방법
    2.1 가중응집제(Ballasted flocculant, BF)
    2.2 가중응집제를 첨가한 슬러지 침전 및 탈수 실험
3. 결 과
    3.1 가중응집제 투입에 따른 슬러지 침전성 변화
    3.2 형상분석을 기반으로 한 슬러지 특성 변화
    3.3 가중응집제가 활성슬러지 탈수성에 미치는 영향
    3.4 가중응집제 첨가에 따른 슬러지 탈수성 개선 원인 분석
4. 결 론
References

• 양혜지(충남대학교 환경IT융합공학과) | Hyeji Yang (Department of Environmental IT Convergence Engineering, Chungnam National University)
• 김용범(충남대학교 환경IT융합공학과) | Yongbum Kim (Department of Environmental IT Convergence Engineering, Chungnam National University)
• 최영균(충남대학교 환경IT융합공학과) | Younggyun Choi (Department of Environmental IT Convergence Engineering, Chungnam National University) Corresponding author