초록 ▼

돈분뇨와 열처리된 음폐수를 혐기소화하여 배출된 고형물을 퇴비화시 비효성분을 높이고, 수분조절을 위한 부재의 사용을 줄이기 위해 생산퇴비를 수분조절재로 재사용하여 가축분 퇴비기준인 염산불용해물25%이하, 유기물대 질소의비 45이하, 유기물 함량 30%이상, 수분 함량 55%이하, 부숙완료, E. coli 0157:H7 살모넬라 균 불검출의 모든 항목을 충족시켰다. 또한 일반적인 퇴비화 방법의 가장 큰 문제점으로 거론되는 악취물질의 휘산을 방지하기 위해 전처리 혐기발효조와 후처리 호기발효조를 조합한 퇴비화 기술을 도입해서 단독으로 호

돈분뇨와 열처리된 음폐수를 혐기소화하여 배출된 고형물을 퇴비화시 비효성분을 높이고, 수분조절을 위한 부재의 사용을 줄이기 위해 생산퇴비를 수분조절재로 재사용하여 가축분 퇴비기준인 염산불용해물25%이하, 유기물대 질소의비 45이하, 유기물 함량 30%이상, 수분 함량 55%이하, 부숙완료, E. coli 0157:H7 살모넬라 균 불검출의 모든 항목을 충족시켰다. 또한 일반적인 퇴비화 방법의 가장 큰 문제점으로 거론되는 악취물질의 휘산을 방지하기 위해 전처리 혐기발효조와 후처리 호기발효조를 조합한 퇴비화 기술을 도입해서 단독으로 호기발효상을 운영할때보다 복합악취는 7배 이상 감소, 암모니아 평균 농도는 9.3% 감소 시켰다. 복도식 탈취실의 탈취 효율은 탈취수에 따라 크게 달라지는데 암모니아 저감 미생물 consortium을 탈취수와 혼합하여 분무할 경우 일반 탈취수 대비 암모니아 저감능 100% 및 탈취수 교체시기 2주에서 4주로 약 2배 연장의 결과를 나타냈다. 11개월 이상의 현장실험을 통하여 최종적으로 SS 28.5mg/L, BOD 17.4mg/L, T-N 67.2mg/L, T-P 0mg/L 의 결과를 얻었으며, 가축분뇨 방류수 수질기준 중 수질정화지역 내의 기준뿐만 아니라 협약과정에서 제시한 목표치 모두 만족스럽게 충족하는 결과를 얻었다. 정화처리 폭기조에 액막화 기법을 도입하여 폭기조 내의 용존산소(DO)를 일반 폭기방법(DO 2.0mg/L)에 비해 20% 증가한 2.5mg/L로 높게 유지시키면서 질산화 효율을 평균 19% 상승시켰다. 또한 동일 규모의 정화처리사보다 1,680kW/month 의 전기를 절감할 수 있었다. 혐기소화폐액은 40℃의 고온으로 유입되어 동절기에는 운전에 유리하지만, 하절기에는 폭기조의 수온이 40℃이상 상승하여 정화처리 효율이 급격히 저하되었다. 최조 계획인 폭기조의 수위조절로 동절기와 하절기 수위를 달리 운전하였으나 수온 제어에 어려움이 있어 폭기조의 산기관과 연결된 관에 냉각수를 이용한 워터자켓을 설치하여 하절기 43℃로 상승했던 수온을 35℃ 전후로 유지시켜 주면서 방류수 수질도 정상을 회복하였다.

Abstract ▼

Ⅳ. Results
1. Treatment of anaerobic digester effluent
This research involved technology for treatment of anaerobic digester wastewater (effluent) containing high concentrations of nitrogen. During 15 months (2013/08–2014/10) operation of this demonstration facility, the final effluent was abl

Ⅳ. Results
1. Treatment of anaerobic digester effluent
This research involved technology for treatment of anaerobic digester wastewater (effluent) containing high concentrations of nitrogen. During 15 months (2013/08–2014/10) operation of this demonstration facility, the final effluent was able to satisfy the water quality standard for livestock wastewater. Except for the initial period of operation, the average values for SS, BOD, T-N, and T-P during 11 months of operation were 28.5, 17.4, 67.2, and 0 mg/L, respectively. These results also met or exceeded the objectives of this research (SS 30 mg/L, BOD 28.8 mg/L, T-N 145.2 mg/L, T-P 17.4 mg/L).
Using fluid-film technology, the DO in the aeration tank was maintained at 2.5 mg/L. (It was 2.0 mg/L in the experimental-control aeration tank.) As a result, the efficiency of nitrification increased 19% (over the control) and the operation period shortened to 18 days (this took 25 days in a general wastewater-treatment system). This was achieved by circulating the volume of wastewater 20 times from the aeration tank to the anaerobic tank and back again. Air blowers of 7.5 kW/d capacity were installed in each aeration tank. The blowers were operated concurrently in both the fluid-film tank and control aeration tank, in two modes: 20 min idle and 40 min operation. Considering the capacity of the fluid-film tank (15 ㎥/d),there was a reduction of 1680kW of electricity used in one month, compared to a general wastewater treatment system with the same capacity.
The optimal temperature of the anaerobic digester fluid was about 40 ℃, this temperature was sustainable during winter operation; however, the summer temperature of the aeration tank increased to 43 ℃. This caused the wastewater treatment efficiency to decrease drastically. Controlling the level (depth) of wastewater in the tank did not allow for control of the temperature of the wastewater. Contrary to our expectation, even an increase in depth of about one meter (3.5 m in January; 4.5 m in July) did not reduce the increase in the water temperature. For this reason, a water-jacket containing circulating cold water was installed and operated on the inlet of the blower. After this, the temperature in the aerobic tank decreased from 43 to 35 ℃ and the wastewater quality recovered to normal.
2.Composting of the solid product from anaerobic digestion of swine excretion and heat-treated food waste
This research, involved technology for composting the solids produced by the anaerobic digestion of merged streams of swine excretion and heat-treated food wastes. To increase the fertilizer content and decrease the amount of water consumed, the compost produced was added as a water controlling conditioner. The result was a high-grade product that met the standard for animal manure compost (insoluble chloride > 25%; ratio of organics to nitrogen < 45%; the organic content > 30%; water content >55%; completion of decay;E. coli 0157:H and Salmonella not detectable).
Generally, the main problems related to composting are the bad odor released by frequent use of the blower, and the use of a substantial amount of electricity. In order to prevent odor from release of volatile substances, a serial process of two steps was provided: a pre-step of anaerobic fermentation and a post-step of aerobic fermentation. When parallel fermentation was conducted simultaneously, the concentration of complex odors from the anaerobic fermentation compost was seven times less than that of the aerobic fermentation compost. A 9.3% reduction was observed in the average concentration of ammonia in the anaerobic fermentation compost, compared with the aerobic fermentation compost. Therefore, the anaerobic/aerobic parallel fermenters were needed to achieve effective composting with less odor and less use of electricity.
To investigate composting-related microorganisms, total genomic DNA was extracted, from samples in the anaerobic and aerobic compost piles, and PCR-DGGE performed. DNA was extracted from the DGGE fingerprint using 31 representative bands, and PCR was performed. The PCR products were cloned and transformed. Plasmids were extracted from 28 transformed clones and their base sequences were analyzed. Next, the results were compared to the GenBank database; then used to draw a phylogenetic tree. There were four groups. Some microorganisms occurred in the anaerobic digestion and biogas production processes, other microorganisms appeared in the composting process, others showed up in anaerobic sludge, and thermophilic microorganisms were present in swine excretion.
One side of a corridor-type deodorizing room was a shared wall with the compost depot, and fans on the wall blew odors from the compost depot into the deodorizing room. Odors produced in the row material inlet, the anaerobic digester waste-storage tank, and in the wastewater-treatment process, were transferred to the deodorizing room by connecting lines. There, they were deodorized by water sprayed from the ceiling of the room. However, because the odor-causing materials dissolved and accumulated in the water, the deodorizing efficiency decreased after two weeks. Therefore, it was necessary to change the water every two weeks to obtain effective odor removal. A microbial consortium of three species (Stenotrophomonas maltophilia, Brevundimonas diminuta, and Pseudomonas aeruginosa) is able to remove ammonia effectively, which was the main odor source from the composting and wastewater-treatment processes. When the microbes were used to treat water previously in service for deodorizing, the ammonia was completely removed. When the microbial consortium was mixed with the water currently being used for deodorizing, the replacement time was extended to four weeks.