생물배양조 부착-활성슬러지법(EBSTS)을 이용한 오수처리에 관한 연구

Abstract

[한글]

우리나라에서는 대부분의 상수원을 지표수에 의존하고 있고,하수도 보급율을 앞지르는 오염부하량에 대처하기 위해서 생물학적 처리방법을 사용하여 왔으나 유량에따른 처리효율의 유동성,계절별의 영향,과다한 슬러지 발생,운전ㆍ관리상의 문제점들이 대두되어 근래에는 이러한 기존 처리공법의 단점을 보완한 Bioreactor system에 관한 연구들이 나타나고 있다.

본 연구에 사용된 생물배양조부착-활성슬러지법(External Biocultivation sewage Treatment System;이하 EBSTS)은 저장조,유량계,폭기조,침전조,반송조로 구성된 활성슬러지 시스템에 메디아를 충진한 생물배양조를 폭기조 외부에 설치한 활성슬러지의 변법이다. 생물배양조의 성분을 조사해 보면 다량의 물과 규소 및 유기물로 구성되어 미생물이 선택적으로 배양,활성회될 수 있도록 환경을 만들어 주었다. 이러한 원리를 가진 EBST을 생활하수에 적용하였을때 95.6%의 제거효율을 나타내며,활성슬러지에서 문제점으로 나타난 악취 발생을 감소시킬 수 있는 흡착 능력과 하폐수농도 변화에 영향을 받지 않으며 잉여 슬러지의 토양 환원이 가능한 생물학적 처리 방법으로 보고하였다.

따라서, 본 연구에서는 서울시 모 종합 병원의 오수를 대상으로 현재까지 사용되는 활성슬러지법과 EBST을 이용하여 유기물 제거효율을 비교,분석하고자 하였으며 수리학적 모델식을 사용하여 BOD 제거속도 상수,미생물 합성계수, 자기소화 계수를 구하여 이론적인 유기물 제거효율을 구하여 보고자 하였다.

이상의 내용으로 수행한 본 연구결과는 다음과 같다.

1.유입수에서의 BOD 295.6mg/L, COD 161 mg/L, SS 199.2mg/L였으며 pH 7.83, 온도 20.7℃,유량 500 L/day로 유입시켰으며, 반송률이 유입수의 27%일 경우 유입 SS는 397 mg/L, MISS 1900 mg/L, 반송조내의 SS는 7412mg/L였다.이때 F/M 비 0.32, BOD 용적부하는 0.50, SRT 일평균 10.9일로서 일반적인 Data와 일치함을 보였다. SVI와 MISS농도는 슬러지 벌킹때를 제외한 정상적은 상태에서 137,1712mg/의 값이 활성슬러지법에서 나타났으며 일반적인 도시하수와 일치함을 볼 수 있었다.

2.EBST에서 유입수 BOD,COD,SS,pH,온도는 285.1mg/L,188.7mg/L,306.1mg/L,7.95,20.3℃로 활성슬러지의 유입수와 거의 유사함을 보였으며, 유량도 활성슬러지와 같은 조건으로 실험하였다. 반송률 27%, F/M비 0.10,BOD용적부하 0.49, SRT는 일평균 14.2일 SVI 92.1, MISS 4236.4mg/L로 나타났다.

3.위 실험결과와 같이 F/M비,BOD용적부하,SVI는 활성슬러지법에서 노은 값을 보인반면 EBST에서는 MISS농도가 2500mg/L더 높은 값으로 측정되었으며 SRT는 일평균 14.2일로 3.3일 더 긴 시간을 요하였다.

4.활성슬러지법과 EBST에서 물질별 제거효율을 비교해보면 활성슬러지법에서는 BOD 83.5%,COD 82.2% SS 83.0%로 나타났으며,EBST에서는 BOD 91.1%,COD 88.8%, SS 89.1%이상으로 활성슬러지법보다 우수하게 나타났다.

5.활성슬러지법과 EBST에 의한 유기물 제거의 수학적 모델식중 미생물 합성계수 K₂와 자기소화계수 b(0.20,0.21),(1.329h-1,1.405h-l)로 유사함을 나타내었으나 BOD 제거속도는 K₁는 활성슬러지법에서 0.014d-1,EBST는 0.067d-l로 활성슬러지법 보다 BOD제거속도가 빠른 것으로 나타났다.

이상의 결과에서 미생물의 종류가 여러가지가 존재하는 활성슬러지법과 메디아를 이용해 선택적으로 미생물 배양,활성화시킨 EBST를 이요해 나타난 유기물 제거효율을 비교해보면 SRT가 길수록,MISS,BOD 용적부하가 클수록,F/M비가 감소할수록 활성슬러지법 보다 EBST에서의 BOD 제거효율이 약 7.6%효과적인것으로 나타났다.이는 실측치만이 아닌 수리학적 모델식을 이용한 이론치에서도 유기물 제거효율을 예측할 수 있었다.

[영문]

Most of all water supply rely on surface waters in Korea.

To cope with the increasement of sewage which surpasses the supplying rate for sewage pipes,the biological treatment of sewage has been used.

However,the Bioreactor system compromising those defaults has been being studied in nowadays,because of the variation of treatment efficiency due to flux,dependence by seasons,occurance of excess sludge,and difficulties of operation and management

in biological treatment.

External Biocultivation Sewage Treatment System(EBSTS) is a modification of activated sludge treatment system,consisting of storage tank,flow meter,aeration tank,and settled and return tank,and installing bio-cultivation which was packed media out of aeration tank.

Investigating components in bio-cutivation,they are made up of water,silica and orgnic matters,which can incubate and activate selecting microorganisms.

Applying EBST using this principle to sewage,removal efficiency showed 95.6% and ther are no effects on absorption capacity and variation of sewage and sewage and wastewater concentration reduced occurrence of undesirable odor.

EBST has been reported as a biological treatment,which is possible to reduce excess sludge in soil.

This study compared and analyzed removal efficiency of organic matters between activated sludge treatment system which has been used by now and EBSTS, and theoretical one calculated by BOD removal rate constants, microorganism synthetic coefficient and self-digestion coefficient was obtained by mathematical model

equation.

The result are summarized as follows;

1.The conditions of influent were BOD 295.6 mg/L,COD 161.6 mg/L and SS 199.2 mg/L, pH 7.83,trmperature 20.7℃,flow rate 500 L/dat.

When the recycling rate was 27% of influent, SS was 397 mg/L, MISS 1900 mg/L and SS in return tank was 7412 mg/L. Then,F/M ratio was 0.32,BOD loading rate,o.50 and daily average SRT,10.9 days,they are consistent to general data.

SVI and MISS concentration were 137 mg/L and 1712 mg/L,respectively in normal condition except sludge bulking in activated sludge treament system,which are correspond to those of civil sweage.

2.In influent of EBST,BOD,COD,SS ,pH,temperature were 285.1 mg/L, 188.7 mg/L, 306.1 mg/L, 7.95 and 20.3℃,respectively,which were similar to those of activated sludge treatment system and influx was the same condition that activated sludge treatment system.Recycling rate,F/M ratio,BOD loading rate,daily average SRT,SVI and MLSS concentration were 27%,0.10,0.49,14.2 days,92.1 and 4236.4 mg/L, indivually.

3.From these results,F/M ratio,BOD loading rate and SVI were higher in EBST than in activated sludge treatment system and MLSS concentration dertermined by 250 mg/L,which was higher than that of activated sludge treatment system. The daily average SRT was 14.2 days which was required 3.3 days more longer than that of

activated sludge treatment system.

4.Comparing with removal efficiencies between activated sludge treatment system and EBST,they were 83.5% for BOD, 82.2% for COD and 83% for SS in activated sludge treatment and above 91.1% for BOD, 88.8% for COD and 89.1% for SS in EBST. The latter is superior to the former.

5.Among mathematical model equation on removal of oraganic matters by activated sludge treatment and EBSTS, microorganisms synthetic coefficient,K2 and self-digeston coefficient,b were 0.20 and 1.392 hr-1 for activated sludge treatment system, and 0,20 and 1.405 hr-1 for EBSTS, which were similar to each other.

However,the removal rate of BOD, K1 was 0.014 day-1 for activated sludge treatment system and 0.067 day-1 for EBSTS, which the latter was more rapid than the former.

From these results,comparing with removal efficiencies of organic matters between activated sludge treatment system existing various microorganism species and EBST inclubated and activated selectively microorganism using media, the longler SRT are the higher MLSS concentration, the larger BOD loading rate and the lower F/M ratio, the more effective BOD removal rate are, which is approximately 7.6%.

Also,the removal efficiencies of organic matters by mathematical model equation would be simulated.