• Journal of the Korea Organic Resources Recycling Association
• /
• v.30 no.4
• /
• pp.5-13
• /
• 2022

The current environmental problem is that environmental pollution is accelerating due to the generation of large amounts of waste and indiscriminate consumption of energy. Fossil fuels, a representative energy production fuel, are burned in the process of producing energy, generating a large amount of greenhouse gases and eventually causing climate change. In addition, the amount of waste generated worldwide is continuously increasing, and environmental pollution is occurring in the process of waste treatment. One of the methods for simultaneously solving these problems is the energy recovery from and reduction of organic wastes. Sewage sludge generated in sewage treatment plants has been treated in various ways since ocean disposal was completely prohibited, but the amount generated has been continuously increasing. Since the sewage sludge contains a large amount of organic materials, it is desirable to recover energy from the sewage sludge and reduce the final discharged waste through anaerobic digestion. However, most of the excess sludge is a mass of microorganisms used in sewage treatment, and in order for the excess sludge to be anaerobically digested, the cell walls of the microorganisms must be destroyed first, but it takes a lot of time to destroy the cell walls, so high rates of biogas production and waste reduction cannot be achieved only by anaerobic digestion. Therefore, the pre-treatment process of solubilizing excess sludge is required, and the thermal solubilization process is verified to be the most efficient among various solubilization methods, and high rates of biogas production and waste reduction can be achieved by anaerobic digestion after destroying cell walls the thermal solubilization process. In this study, when pretreating TS 10% thickened excess sludge through a thermal solubilization system, a study was conducted on solubilization characteristics according to retention time and operating temperature variables. The experimental variables for the retention time of the thermal solubilization system were 30 minutes, 60 minutes, 90 minutes, and 120 minutes, respectively, while the operating temperature was fixed at 160℃. The soulbilization rates calculated through TCOD and SCOD derived from the experimental results increased in the order of 12.11%, 20.52%, 28.62%, and 31.40%, respectively. And the variables according to operating temperature were 120℃, 140℃, 160℃, 180℃, and 200℃, respectively, while the operating retention time was fixed at 60 minutes. And the solubilization rates increased in the order of 7.14%, 14.52%, 20.52%, 40.72%, and 57.85%, respectively. In addition, TS, VS, T-N, T-P, NH₄⁺-N, and VFAs were analyzed to evaluate thermal solubilization characteristics of thickened excess sludge. As a result, in order to obtain 30% or more solubilization rate through thermal solubilization of TS 10% thickened excess sludge, 120 minutes of retention time is required when the operating temperature is fixed to 160℃, and 170℃ or more of operating temperature is needed when the operating time is fixed to 60 minutes.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.11 no.2
• /
• pp.110-116
• /
• 2003

This study was executed to evaluate the utilization and efficiency of the ceramic biocarrier as the promoter of decomposing on the organic matters for the composting using with pig manure by analyzing of the physico-chemical properties during composting. The treatments of this experiment were consisted of the control(C),microorganism(M), M with natural zeolite(M+Z), M with synthesized zeolite(M+SZ), and M with ceramic biocarrier(M+CZ). The process term of composting was conducted for 30days in the rapidly fermented machine(as pilot system). The results of the physico-chemical properties of the composts were as follows. The changes of temperature during composting was not relative with the microorganism and zeolite materials used in the composts. At all of the treatments were similar to changing of temp. from the initial stage to the final stage. But the added microorganism treatments were higher than control. And the entire pH value of treatments were appeared the same that above temperature result, also the M+CZ and M+SZ treatment among the treatment were higher. At the results of T-C, T-N and C/N ratio, in case of T-C value, the M+CZ treatment was highly more decreased than others. However at the T-N value, there were not the differences from the each treatment. And the C/N ratio was changed according to the changes of T-C and T-N value. Especially, at the M+CZ aud M+SZ treatments were remarkably reduced by about 21.4-23.3 value. In the result of G.I for evaluating of the compost humidity, the M+CZ and M+SZ treatments were close up approximately 110 value compared with the control(G.I value 100). Therefore, the examined ceramic biocarrier amended with compost-promoting-bacteria could be applied to the production of many high quality fertilizers. It is also expected that the results of this researches could be applied to the recycle of the organic wastes based on the experimental results of ceramic biocarrier and compost-promoting-bacteria application.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.11 no.3
• /
• pp.87-95
• /
• 2003

Although extensive studies were conduced on hydrogen fermentation of organic wastewaters, little is known about biohydrogen production from organic solid wastes. The leaching-bed reactor treating food waste by heat-shocked anaerobic sludge was, therefore, operated at D of 2.1, 3.6, 4.5 and $5.5d^{-1}$ to find optimal D for hydrogen production. Successful operation of a reactor can be accomplished when it is operated at proper dilution rate (D). Operation at high D leads to the washout of biomass in the reactor while operation at low D leads to product inhibition due to the accumulation of excess VFA. These appear to limit the production of hydrogen to reach a higher level. All the reactors showed that, on day 1-3, hydrogen production was dominant and VFA concentration was higher than ethanol. Butyrate and acetate were major components of VFAs over the whole operation, though lactate was very high on day 1-2. Compared with other D values, D of $4.5d^{-1}$, resulted in higher butyrate/acetae (B/A) ratios during the fermentation. The trend of B/A ratios was similar to the hydrogen production, suggesting that butyrate formation favored hydrogen production. Ethanol increased significantly from day 4 when hydrogen Production stopped. It indicated that heat-shocked sludge was able to induce a metabolic flow from hydrogen-and acid-producing pathway to solvent-producing pathway. Operation at D of $4.5d^{-1}$ led to higher fermentation efficiency (58%) than those (51.5, 55.3 and 53.7%) at 2.1, 3.6 and $5.5d^{-1}$. The COD removed was convened to hydrogen (10.1%), VFA (30.9%), and ethanol (17.0%).

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.9
• /
• pp.870-878
• /
• 2010

We investigated the concentration and the sources of ubiquitous persistent organic pollutants [i.e., 17 toxic polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), 12 coplanar polychlorinated biphenyls (Co-PCBs), and 16 priority polycyclic aromatic hydrocarbons (PAHs)] in waste papers and lumbers from industrial complexes. The total concentrations in waste papers and lumbers ranged from 9.69~176.77 pg/g-dry and 0.14~0.25 pg/g-dry for 17 PCDD/Fs, 109.95~4097.25 pg/g-dry and 28.23~59.88 pg/g-dry for 12 Co-PCBs and 9.30~52.18 ng/g-dry and 0.82~1.82 ng/g-dry for 16 PAHs respectively. Generally, the concentration of these pollutants in waste papers was higher than those in waste lumbers. OCDD was dominant in waste papers and lumbers and the PCDD/F patterns of these samples were similar with that of stack gas. The distribution patterns of Co-PCBs in wastes were related with commercial PCB products, indicating the effect of commercial PCB products on ubiquitous environment. The diagnostic ratios of several PAH compounds in waste paper showed that they were related with pyrogenic sources.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.8 no.2
• /
• pp.130-139
• /
• 2000

Serial basic tests were conducted for the determination of fundamental kinetics and for the actual application of kinetic parameter to food waste digestion with precise measurement of methane production under a thermophilic condition. The effects of food particle size, sodium ion concentration, and volatile solid (VS) loading rate on the anaerobic thermophilic food waste digestion process were investigated. Results of serial test for the determination of fundamental kinetic coefficients showed the value of k (maximum substrate utilization rate coefficient) and KS (half-saturation coefficient) as $0.24hr^{-1}$ and $700mg/{\ell}$, respectively, for non-inhibiting organic loading range. No inhibition effect was shown until $5g/{\ell}$ of sodium ion concentration was applied to a serum bottle reactor. However, the volume of methane gas was decreased gradually when the concentrations of more than $5g/{\ell}$ of sodium ion applied. All sizes of food waste particle showed the same constants (A : 0.45) but the maximum substrate utilization rate constant ($k_{HA}$) was inversely proportional to particle size. As an average particle size increased from 1.02 mm to 2.14 mm, $k_{HA}$ decreased from $0.0033hr^{-1}$ to $0.0015hr^{-1}$. The result reveals that particle size is one of the most important factors in anaerobic food waste digestion. There was no inhibition effect of sodium ion when VS loading rate was $30g/{\ell}$. And maximum injection concentration of VS loading rate was determined about $40g/{\ell}$.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.3 no.2
• /
• pp.79-89
• /
• 1995

Changes of microbial activity and physicochemical environment during composting of papermill sludge(PMS) in the pilot plant equipped with an agitated bed reactor were monitored for establishing the efficient composting system. Microbial activity determined as the evolution of $CO_2$ increased for the first 10 days after introduction of PMS to the reactor and decreased thereafter. Population changes of microorganisms in the reactor-PMS were not typical as in windrow system. The ratio of thermophilic bacteria to mesophilic bacteria, however, increased slowly even 23 days after introduction. Temperature of PMS increased rapidly from the first day and reached $62^{\circ}C$ at 7 days after introduction and decreased slowly thereafter. The acidity of PMS was pH 6.8 initially, increased to pH 8.0 after 7 days and decreased to pH 7.4 after 23 days. Redox potential(Eh) of PMS was -320mV at the beginning of composting, but it was increased with time to reach -15mV after 23 days composting. However, Eh of PMS pre-sterilized before measurement was average 50mV, regardless of composting periods indicating the major role of microorganisms during composting process. Water content of PMS was 67% initially and decreased to about 50% after 23 days composting in the reactor. Less than 13 days-old compost inhibited growth of radish in the container mixture with bed soil. Based on statistical analysis of microbial and physicochemical parameters of PMS during composting, an equation was developed for determining compost maturity. A number of experiments using various organic wastes are required before application of the formular to the practical use.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.20 no.4
• /
• pp.75-85
• /
• 2012

This study was investigated to develop an alternative medium for the cultivation of oyster mushrooms. The cultivation characteristics for major cultivated varieties of oyster mushrooms were campared with the food waste medium. In addition, water control & a gap formation of food waste is being pointed out as a problem of the medium material. Therefore, certain amounts of earthworm casting were supplied to the food waste medium to overcome the water and compaction phenomenon. This study investigated the use of the total 6 cultivars of oyster mushrooms, the Suhan(PL.1), Chiak No. 5(PL.2), Chiak No. 7(PL.3), Samgu No. 5(PL.4), Samgu No. 8(PL.5), Jangan No. 5(PL.6). In terms of medium, the optimum growth of the mycelium of the oyster mushroom was observed in the beet pulp medium but in food waste, the mycelium's growth was observed as insufficient in the bulk of cultivars. The Jangan No. 5(PL.6) was superior to other cultivars relative to the mycelium's growth. The optimum concentration of earthworm casting added the foodwaste medium was 30%. When Jangan No. 5(PL.6) was incubated in the foodwaste meidum containing 30% earthworm casting, the early days to germination were long, almost double the amount of time than that of the beet pulp medium. However, it was found that the fruit body size was larger than that of the beet pulp by up to 20.5%, and the length of the fruit body was up to 6.2% longer than that of the beet plup. The total yields increased by 60.5%. The analysis results of the oyster mushroom's nutritional contents cultured using the food waste medium, shows that the protein, vitamin A and vitamin E increased 70.6%, 2.4%, 0.8% respectively, the fat decreased by 12.6% and the oleic acid increased in a very small amount compared to that of the beet pulp medium.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.15 no.4
• /
• pp.115-124
• /
• 2007

The material compressions in the vertical composting reactor affect to the biodegradation rates of the organic wastes. This study investigated the variations of physical properties of the composting materials according to the height of reactor due to affect to the settlement in the vertical composting reactor. The variations of decreased temperature after peak temperature showed the different patterns depending on the reactor heights. The variation width of re-increased temperature after peak temperature was reduced as the mixing operations were increased, and increased as the height of reactor elevated. The moisture content and the variation width of the moisture content were increased higher as the height of the reactor became higher. The variations of the bulk density at each height of vertical reactor showed the same tendency comparing with those of the moisture content. The relationship between bulk density and moisture content had shown the quadratic equation (r2=0.94). The dry solid contents at each reactor height were decreased as the height of reactor were increased. The results of the variation of the physical properties during the composting process were caused by the downward compression of the material into the reactor. Settlement rate in the vertical composting reactor was estimated about 2.184cm/day. To increase the biodegradation efficiency in the vertical reactor, the conditions of air path in the composting material matrix have to be investigated afterwards.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.25 no.2
• /
• pp.41-48
• /
• 2017

A vertical multi-stage ammonia stripping reactor using E-PFR, which has been proved to be superior in anaerobic and aerobic treatment, was developed and a lab scale experiment was conducted. According to the change of stage number condition, the removal rate of the ammonia nitrogen in the reactor with 0-stage was about 52.5% after 8 hours (pH 10, temperature $35^{\circ}C$, and the air/liquid ratio $3min^{-1}$) However, in the reactor with 5-stage, the removal efficiency was about 62.6%. According to the change of pH condition, the removal rate of ammonia nitrogen was about 42.6% at pH 9 after 8 hours, and was about 74.4% at pH 11 (5-stage reactor, temperature $35^{\circ}C$, and the air/liquid ratio $3min^{-1}$). According to the change of temperature condition, the removal rate of the ammonia nitrogen was about 51% at $25^{\circ}C$ after 8 hours (5-stage reactor, pH 10, and the air/liquid ratio $3min^{-1}$), and was about 87.2% at $45^{\circ}C$. According to the change of air injection volume condition, the removal rate of the ammonia nitrogen was about 45.8% at $2min^{-1}$ after 8 hours (5-stage reactor, pH 10, and at $35^{\circ}C$). and was about 75% at $4min^{-1}$. Based on these results, we will follow up the applicability of the actual plant in the future through continuous operation evaluation.