초록 ▼

사상성 조류인 HR(Hydrodictyon Reticulatum)을 적용하였으며, HR은 원통 모양의 다세포성 조류로 수㎝까지 성장하여 간단한 여과장치만으로 수확이 가능해 경제적인 문제와 가용화율의 문제를 모두 해결할 수 있는 조류로 bucket wheel 수확설비를 개발하여 HR을 수확하였다. Bucket wheel 수확설비는 기존의 wheel을 변형하여 개발된 기술로 교반장치로 활용이 가능하여 별도의 교반시설과 기계설비, 설치부지가 불필요하다는 큰 장점을 가지고 있으며, 부상분리방법대비 초기투자비와 유지관리비를 50%이상 절감할

사상성 조류인 HR(Hydrodictyon Reticulatum)을 적용하였으며, HR은 원통 모양의 다세포성 조류로 수㎝까지 성장하여 간단한 여과장치만으로 수확이 가능해 경제적인 문제와 가용화율의 문제를 모두 해결할 수 있는 조류로 bucket wheel 수확설비를 개발하여 HR을 수확하였다. Bucket wheel 수확설비는 기존의 wheel을 변형하여 개발된 기술로 교반장치로 활용이 가능하여 별도의 교반시설과 기계설비, 설치부지가 불필요하다는 큰 장점을 가지고 있으며, 부상분리방법대비 초기투자비와 유지관리비를 50%이상 절감할 수 있는 것으로 평가되었다.
자연채광기술을 이용하여 반응조 내부에 태양광과 LED을 이용한 인공광을 복합적으로 공급할 수 있는 복합광 심층조사 설비를 개발하였다. 복합광 심층조사 설비는 외부 광량이 350㎛ol/㎡‧s이상일 때에는 태양광만을 조사하며, 350㎛ol/㎡‧s이하로 태양광이 저하되면 단계별로 LED 전등이 발광하여 수중에 약 75㎛ol/㎡‧s내외의 광량을 공급하는 설비이다. 본 설비의 적용을 통해 기존 개방형 반응기의 최대 수심 30㎝를 50㎝이상으로 증가시켜 소요부지를 절감하였으며, 수중 조사광량을 150%이상 증가시켜 미세조류의 성장량은 25% 이상, T-N과 T-P 제거효율은 각각 5%와 10% 향상시켰다. 경제성 분석결과, 본 개발기술은 적은 인공광원 운영시간과 긴 설비수명으로 기존 인공광원들의 전력비 대비75%이상, 유지관리비 대비 50% 이상을 절감할 수 있는 것으로 평가되었다.
미세조류 배양에 필요한 항목들을 실시간으로 모니터링 하여 제어할 수 있는 통합생산관리시스템을 개발하였다. 통합생산관리시스템은 크게 모니터링시스템과 배양관리시스템으로 구성되어 있으며, 모니터링 시스템은 운영자가 실시간으로 제공되는 상태정보와 과거정보를 이용하여 운영 설정한 인자값에 따라 반응조를 실시간으로 제어하는 시스템이며, 배양관리시스템은 미세조류의 투입 시점부터 수처리 전과정과 바이오 에탄올 생산량 관리하는 시스템이다. 본 시스템의 개발의 통해 안정적인 방류수질과 단위면적당 높은 미세조류 생산성을 확보할 수 있었다.
핵심기술인 미세조류를 이용한 하수고도처리공정은 국내에 1㎥/일 규모의 pilot plant와 미얀마에 72㎥/일 규모의 pilot plant를 이용하여 개방형으로 개발하였다. 국내의 pilot plant는 복합광 심층조사 설비를 결합하여 기존 개방형반응기의 문제인 넓은 소요부지 문제를 해결한 Highrate Open Pond 기술이다. Pilot plant의 장기 운영을 통하여 계절별, 광량, 수온, 체류시간, 탄소원 공급 유무에 따른 수처리 성능과 HR의 성장률을 분석하여 최적 운영인자와 설계인자를 도출하였다. 동절기에 pilot plant를 수온 20℃, 체류시간 6일, 탄소원(NaHCO3) 100㎎/ℓ를 공급하여 운영한 결과, T-N은 평균유입농도 9.5㎎/ℓ를 평균 4.5㎎/ℓ로 방류하여 평균 51.4%의 제거효율 나타내었고 T-P의 경우에는 평균 0.60㎎/ℓ가 유입되어 평균 0.18㎎/ℓ로 방류하여 평균처리효율은 69.3%를 나타내어 목표방류수질을 달성하였다. 동절기를 제외한 다른 계절에서는 체류시간에 차이가 있으나, 일반적으로 체류시간 4일, 탄소원 100㎎/ℓ를 공급하여 운영할 경우, T-N은 평균 8.6㎎/ℓ로 유입되었고 평균 2.7㎎/ℓ로 방류되어 평균67.6%의 제거효율을 나타내었으며, T-P의 경우, 평균 0.83㎎/ℓ가 유입되었고 평균 0.10㎎/ℓ로 방류되어 평균 87.0%의 제거효율을 나타내었으며, 목표수질기준을 만족하였다.
해외(미얀마)Pilot plant에서는 다양한 유입원수를 대상으로 HR의 현지 적용 가능성을 평가하였고 seed의 대량 생산 방안을 검토하였다. 실험결과, 교반시설을 설치할 경우, 미세조류의 성장량이 약 16% 증가하며, 체류시간을 4일에서 3일로 단축하여 운영할 경우, 미세조류 성장량은 약 21.4% 증가하는 것으로 평가되었다. HR seed 생산의 경우, 대형 배양조를 10개의 소배양조로 분리하고 스크린 시설을 설치하여 운영할 경우, 미세조류 성장량이 약 35% 증가시킬 수 있는 것으로 조사되었다. 하수원수성상을 이용하여 수처리 성능을 평가한 결과, T-N의 평균 유입농도는 29.7㎎/ℓ이었고 평균 방류농도는 4.4㎎/ℓ로 평균제거효율은 85.0%로 나타났으며, T-P의 경우에는 평균 유입농도 5.82㎎/ℓ, 평균 방류농도는 0.37㎎/ℓ로 평균 제거효율은 93.6%의 처리성능을 나타내어 평균 기온이 높고 일조량이 많은 동남아시아에서는 기존 하수처리시설을 대체하는 기술로 적용하는 것이 가능할 것으로 판단되었다.

Abstract ▼

Ⅳ. Result of R&D
At the result of analyzing the present condition of WWTP, as of the end of the year 2010,public WWTP in operation with the capacity of 500㎥/day and more are a total of 470 plants. 85% among them, 401 are being run from being applied by the advanced treatment method. But, from Jan

Ⅳ. Result of R&D
At the result of analyzing the present condition of WWTP, as of the end of the year 2010,public WWTP in operation with the capacity of 500㎥/day and more are a total of 470 plants. 85% among them, 401 are being run from being applied by the advanced treatment method. But, from Jan. 1, 2012, since the legal effluent water quality standard of phosphorus of public WWTP was strengthened maximum 0.2㎎/ℓ, most public WWTP are being run by introducing the third chemical treatment facilities. Accordingly, because it is expected that cost of chemicals will increase over 180 billion won yearly among operation expenses of the WWTP, development of relevant technology was an urgent situation.
The technology of advanced wasterwater treatment process using previous microalgae was developed mostly using unicellular microalgae. Generally, unicellular microalgae is 30㎛ and under in size. Similar to the specific gravity of water, it was harvested through methods of centrifugation or flotation. Due to this, a lot of harvestingexpenses are needed, qualitative change occurs from the use of chemicals, solubilization rate becomes deteriorated in the following process. Harvesting problems are known to be the biggest drawback in commercializing microalgae. In this assignment, HR (Hydrodictyon Reticulatum) as filamentous algae was applied in order to solve this Harvesting problem.
HR is cylindrical multicellular algae. Because it grows up to a few cm, harvesting it is possible only with simple filtering equipment. So, it is algae to solve the economic problem and the solubilization problem. By developing bucket wheel harvesting facilities, HR was harvested. The bucket wheel harvesting equipment is technology which was developed from transforming previous wheels and is possible as agitators in use. They have big merits that agitation facilities, machine equipment, and installation lands are unnecessary. It was evaluated to reduce initial investment and maintenance expenses 50% and more compared with the flotation method.
In case of Korea, daylight hours are lack in 500 hours and more annually in comparison with other countries. Though the advanced wastewater treatment technology using microalgae has been developed, it is in a situation that target areas of the installation cannot avoid being restricted due to high deviation between daylight hours and light quantity. Plus, in case that the concentration of microalgae increases, the water depth of reactors is restricted caused from self-shading effect. Because of it, there is a problem that lots of required sites should be needed. Lately, to solve these problems, a lot of research cases that artificial light sources are applied are being announced, but it is known that they are not realizable from low economic feasibility.
In this assignment, in order to solve these problems, hybrid lighting systems were developed that artificial light can be supplied from LED and natural light can be inside reactor through a transparent cylinder. The hybrid lighting system irradiate natural light only when outside light quantity is 350㎛ol/㎡‧s and more. When natural light decreases under 350㎛ol/㎡‧s, LED lamps light up by stage. So, they are facilities to supply light quantity around 75㎛ol/㎡‧s into water. Through the application of the facilities, the required sites could be reduced from increasing the maximum 30cm water depth up to 50cm and more of previous open-type reactors. By enhancing the underwater light quantity 150% and more, the growth rate of microalgae and the removal efficiency of T-N and T-P were increased 25% and more, 5%, and 10%, respectively.
At the analysis result of economic feasibility, this development technology was evaluated to reduce 75% and more compared with the previous artificial light sources in electric power and 50% and more in maintenance cost owing to low operation time of the new artificial light source and long life time of the new facilities.
As domestic and foreign technology related with microalgae is focused on the production and fuel extraction of microalgae, studies on light, gas (CO2) transfer, badge supply are being conducted a lot. About the technology field of the production control system to enhance production efficiency of biomass, rudimentary stage’s researches are being realized, centered on enclosed reactors. But, it is in a situation that researches on open facilities are almost none.
In this study, from monitoring items necessary for the cultivation of microalgae in real time, a integrated production control system to control them was developed. The integrated production control system is largely composed of a monitoring system and a cultivation control system. The monitoring system is a system to control reactors according to factor values which were set operationally using state information and past information provided in real time. The cultivation control system is a system to control the whole course of water treatment and the production amount of bio ethanol from the input time of microalgae. Through this system’s development, stable effluent water quality and high productivity of microalgae per unit area could be secured.
The advanced wasterwater treatment process using microalgae as core technology was developed in an open type using pilot plants with the sizes of 1㎥/day in Korea and 72㎥/day in Myanmar. The domestic pilot plant is high-rate open pond technology which solved the problem needing a broad required land as a problem of previous open-type reactors, from combining hybrid lighting system. Through long-term operation of the pilot plants, optimal operation factors and design factors were extracted by analyzing the growth rate of water treatment performance and HR according to each season, light amount, water temperature, HRT, and existence or not of the supply of a carbon source.
In the winter time, at the result of supplying 20℃ water temperature, 6-day HRT, and 100㎎/ℓ carbon source (NaHCO3); by discharging T-N average 4.5㎎/ℓ of average inflow concentration 9.5㎎/ℓ, removal efficiency of average 51.4% was represented. In case of T-P, average 0.60㎎/ℓ was flowed in and average 0.18㎎/ℓ was discharged. The average treatment efficiency was 69.3% and the goal effluent water quality was achieved.
In other seasons except winter, there is difference in HRT. Generally, in case that the pilot plant is run with 4-day HRT and 100㎎/ℓ carbon source (NaHCO3), T-N was flowed in average 8.6㎎/ℓ and discharged average 2.7㎎/ℓ, so 67.6% removal efficiency was presented. In case of T-P, average 0.83㎎/ℓ was flowed in and average 0.10㎎/ℓ was discharged, so average 87.0% of removal efficiency was showed. Therefore, the goal standard of water quality was satisfied. The growth quantity of microalgae of winter and other seasons was 4.11g/㎡‧d and 8.34g/㎡‧d per unit area respectively based on dry weight.
The foreign pilot plant with the scale of 2㎥/day installed in Myanmar was constructed as traditional open-type facilities due to the local situation. But, the facilities were supplemented consistently because the growth of microalgae was hindered due to excessive supply of light quantity and continuous pollution occurred from the cornering phenomenon caused by winds and the inflow of external substances. In the pilot plant, targeting diverse raw waters flowed in, local application possibility of HR was evaluated and plans of mass production were examined.
At the test result, it was evaluated that the growth rate of microalgae increased about 16% in case of the installation of stirring facilities. In case of the operation from lessening the HRT from 4 days to 3 days, it was appraised that the growth rate of microalgae increased about 21.4%. At the result of evaluating water treatment performance using artificial wastewater, the average inflow concentration of T-N was 29.7㎎/ℓand the average effluent concentration was 4.4㎎/ℓ. The average removal efficiency was 85.0%. In case of T-P, the average effluent concentration was 5.82㎎/ℓ and the average effluent concentration was 0.37㎎/ℓ. So, the average removal efficiency was 93.6% of treatment performance. It was judged that to apply the technology substituting previous WWTP was possible in Southeast Asia with lots of light quantity.