We used a conventional activated sludge process to treat a paper wastewater, and then the effluent was treated with an ozone oxidation process as advanced process to remove non-degradable materials. It was found that the removal efficiency rates of the organic matter has been rapidly increased initially, and then it was almost constant after this period. The concentration of ozone should be recommended to maintain approximately 8.3 mg/L during this operation to keep the CODmn value below 100 mg/L and ozone contact time longer than 60 min.
활성슬러지 공정을 이용하여 Kraft 펄프공장에서 배출되는 유출수에 잔류하는 만성독성의 제거가능성을 평가하기 위하여 pilot plant를 운전하였다. 독성 이외에도 폐수내의 BOD, SS, resin과 fatty acids, 색도, 그리고 AOX와 같은 오염물질의 제거효과도 측정되었다. Pilot plant는 정상상태에서 약 10주 동안 운전되었으며 운전기간 동안의 평균 F/M 비율은 0.28, 그리고 sludge age는 8.4일로 계산되었다. 평균 MLSS 농도는 4,309mg/l이었으며 이중 휘발성 물질은 57%이었다. 운전기간 동안, BOD 제거계수(k)는 $30^{\circ}C$에서 8.2/일 이었으며 BOD 제거율은 full-scale 운전시보다 3~6% 정도 낮은 84%로 나타났다. 활성슬러지 유출수의 만성독성 시험은 Dinnel 방법과 BML 방법이 활용되었으며, 시험결과 pilot plant 활성슬러지 시스템에서도 효율적인 운전을 통하여 90% 이상의 독성제거가 가능함을 알 수 있었다. Pilot plant의 진 공정을 통해서 색도와 AOX의 제거는 매우 미미하였으나 resin과 fatty acids는 뛰어난 제거율을 나타내었다.
Chemical batch tests were conducted to investigate the amount of nutrients that were released from the wasted activated sludge during microwave heating. For this study, three types of activated sludge were obtained from A2/O, MLE and oxidation ditch (OD) processes. Polyphosphate-accumulating organisms in the activated sludge have a unique trait: they releases phosphate from the cell when they are exposed to high temperatures. The sludge obtained from the A2/O process released the largest amount of phosphate, followed by those from the MLE and OD processes. The release of phosphate increased with increasing polyphosphate content in the sludge under strongly alkaline or acidic conditions. Furthermore, ammonia and heavy metals were released with phosphorous. The largest amount of ammonia was observed from the sludge obtained from the MLE process. The release of heavy metals strongly depends on the pH conditions. Therefore, the chemical analysis results strongly suggest that both phosphorus and ammonia react with Mg2+ or Ca2+ to form metal complexes such as magnesium ammonium phosphate or hydroxyapatite under alkaline conditions.
활성슬러지 공정의 생물학적 반응조 및 2차 침전지 설계와 관련해서 정상상태 설계식(Ekama et al., 1986; WRC, 1984) 및 1-D flux theory 설계식(Ekama et al., 1997)을 사용하여 슬러지 농도에 따라 두 가지 공정을 일괄적으로 설계하였다. 또한, 슬러지 농도에 따른 생물학적 반응조 및 2차 침전지 크기 변화를 도식화하고, 유입수 성상이나 슬러지 침강성, 환경 및 운전조건 그리고 첨두유량이 각 공정의 크기결정에 미치는 영향을 평가하였다. 먼저 유입수의 특성과 관련하여 난분해성 용해성 물질(fs,us)은 반응조 크기 결정에 큰 영향이 없었지만, 난분해성 입자성 물질(fs,up), 무기 고형물(fi) 및 유기물 강도(Sti)의 영향은 크게 나타났다. 운전인자인 Sludge Retention Time(SRT)의 경우, 슬러지 생산량과 관련되므로 반응조 크기결정에 역시 큰 영향을 미쳤다. 2차 침전지의 설계요소인 Sludge Volume Index(SVI) 및 첨두유량이 커질수록 2차 침전지에 수리학적 부하가 커지게 되어, 2차 침전지가 크게 설계되어야 했다. 본 설계과정에서는, 온도 변화가 미치는 영향은 작게 나타났다. 대규모 처리장의 경우 반응조 및 2차 침전지 전체 크기 결정과 함께 1개조 크기의 상한선을 설정하여 개수를 산정하였다. 최종적으로 엔지니어는 여러 가지 슬러지 농도에 대하여 반응조 및 2차 침전조의 크기, 개수 및 현장조건을 고려한 건설비용을 반복적으로 계산하게 되면, 최소비용 설계와 함께 최적의 슬러지 농도를 결정하게 된다.
The behavior of copper throughout the whole process of wastewater treatment plant that uses the activated sludge process to treat the wastewater of petrochemical industry that contains low concentration of copper was investigated. Total inflow rate of wastewater that flows into the aeration tank was 697 m3/day with 0.369 mg/L of copper concentration, that is, total copper influx was 257.2 g/day. The ranges of copper concentrations of the influent to the aeration tank and effluent from the one were 0.315 ~ 0.398 mg/L and 0.159 ~ 0.192 mg/L, respectively. The average removal rate of copper in the aeration tank was 50.8 %.
The bioconcentration factor (BCF) of copper by microbes in the aeration tank was 3,320. The accumulated removal rate of copper throughout the activated sludge process was 71.3%, showing a high removal ratio by physical and chemical reactions in addition to biosorption by microbes. The concentration of copper in the solid dehydrated by filter press ranged from 74.8 mg/kg to 77.2 mg/kg and the concentration of copper by elution test of waste was 2.690 ~ 2.920 mg/L. It was judged that the copper concentration in dehydrated solid by bioconcentration could be managed with the control of that in the influent.
A laboratory experiment was performed to investigate phosphorus and nitrogen removal from synthetic wastewater by intermittently aerated activated sludge process packed with aluminum and silver plate. Three continuous experimental processes, i. e. an intermittently aerated activated sludge process(Run A), an intermittently aerated activated sludge process with an aluminum and silver plate packed into the reactor(Run B), and a reactor post stage(Run C) were compared. In the batch experiments, the phosphorus removal time in the reactor packed with aluminum and silver plate simultaneously was faster than that of the reactor packed with only an aluminum plate. More phosphorus was removed with an increase of NaCl concentration. The pitting corrosion of aluminum does not affect the performance of the biological treatment. The total nitrogen removal efficiency in Run B was 57% and 43.6% at the HRT of 12 and 6 hours respectively. The effluent PO4-P concentration as low as 1.0 mg/L could be obtainable through the continuous experiment in Run B at HRT of 6 hours.
This study was conducted to investigate the treatment of wastewater from acetaldehyde manufacturing plant by activated sludge process with Micrococcus roseus AW-6, Micrococcus luteus AW-22, Microbacterium lacticum AW-38 and Microbacterium laevaniformans AW-41. The COD_Mn and BOD_5 of the wastewater were 5,260㎎/L and 6,452㎎/L, respectively. pH was 1.85. The main organic component in the wastewater was acetic acid which was contained 67,600㎎/L. Optimum dilution time for activated sludge process was shown 10 times. The specific substrate removal rate(K_e) was 1.95day^-1 and the nonbiodegradable matters(S_n) were 23.2㎎/L. Saturation constant (K_e) and maximum specific growth rate(q_max) were 1,640㎎/L and 2.33day^-1, respectively. Sludge yield coefficient(Y) and endogenous respiration coefficient(K_d) were 0.28㎎ MLVSS/㎎COD and 0.02day^-1, respectively. COD_cr removal efficiency was 91% for 1.95day of hydraulic retention time.