• Journal of Environmental Science International
• /
• v.7 no.1
• /
• pp.96-103
• /
• 1998

To study the optimum conditions of composting with industrial wastewater sludge, the variations of temperature and $CO_2$ generation amount during the composting periods were investigated. The conditions were that industrial wastewater added to bulking agents such as sawdust and rice hull was used, and differently treated with microorganism seeding or not, initial C/N ratios, air flow rate and initial moisture contents, respectively. The results were summarized as follows : Seeding 5% of microorganism was higher the temperature than not seeding. And using sawdust as bulking agents, and adjusting 30~40 of Initial C/N ratio, 200ml/l.min. of k flow rate and 67~68% moisture contents were higher the temperature than any other conditions. Seeding 5% of microorganisms was higher $CO_2$ generation amount than not seeding. And that was much in the order of 7~40, 30~34 and 22~23 of initial C/N ratio. Judging from the results, it should be considered that the optimum conditions in the composting of industrial wastewater sludge were seeding of 5% microorganisms, and adjusting 30~34 of Initial C/N ratio, 200ml/l min. of air flow rate and 67~68% of Intitial moisture contents. The contents of inorganic matters and C/N ratio during the composting periods at optimum condition were a little Increased. and heavy metals contents after composting were lower than standard for fortllizer.

• Journal of Energy Engineering
• /
• v.13 no.1
• /
• pp.82-91
• /
• 2004

In order to utilize inorganic components in coal and wastewater sludge as an environmentally stable material, slag-forming is considered as one of the suitable methods better than producing as an ash. Coal slag that was produced by gasification as well as the slag made from wastewater sludge by incineration or melting process have been analyzed with the viewpoint of recyclability. Slags produced by water quenching exhibited a cracked shape that has a size of few millimeters with sharp edges. Slags contain the unburned carbon content below 0.15％ and expose mostly amorphous structural characteristics. Analysis results in the extraction of heavy metal compounds demonstrate that both slags from coal and wastewater sludge could be utilized as a safe recycle material even with a Japanese environmental regulation that is ten times more stringent than the current Korean standard. Slags from coal and wastewater sludge show significant differences in contents of each heavy metal compound. Since the future trend of environmental regulation shifts to the control of total content for each heavy metal compound, proper mixing of slags that contain different heavy metal contents might be an option for manufacturing recycle materials.

• Analytical Science and Technology
• /
• v.12 no.4
• /
• pp.318-325
• /
• 1999

Sludges from the wastewater of hanji production were analysed to see that sludges from the bleaching process, the bleach washing process, and the paper preparation process were fibrous, while sludges from the process cooking with NaOH and the process of final chemical and microbiological treatment were non-fibrous. Sludge solution from the bleaching process had the most amount of solid matters. Sludges from the bleaching process, the bleach washing process, and the final chemical and microbiological treatment process contained about 80-90 %(w/w) moisture. Owing to hypochlorite ion, pH of sludge from the bleaching process was higher than any other sludge samples. The inorganic components of sludges were determined by ICP-AES. The major inorganic component of sludge from the process cooking with NaOH was Na, while the sludge from the bleaching process had Na and Ca, major components in the final chemical and microbiological treatment process were Ca and Al. Trace amount of Mg, Fe, K, P, Mn and Ti were observed in sludges. Sludge from the bleaching process had ashes more than any other sludges. Shape of sludges observed by SEM was appeared to fibrous or crystalline, and the breadth of fibrous sludge was $5{\sim}50{\mu}m$. The sludge from the bleaching process had the most amount of matters soluble by cold and hot water and by alcohol-benzene.

• Environmental Engineering Research
• /
• v.13 no.3
• /
• pp.112-118
• /
• 2008

Residual solid in excess sludge treated by hydrothermal reaction was investigated as raw material for its recycling. Treated excess sludge and residual solid were also focused on their content change during hydrothermal reaction. Two kinds of excess sludge, obtained from a local food factory and a municipal wastewater treatment process, were tested under various conditions. Following hydrothermal reaction, depending on the reaction conditions, biodegradable substrates in treated excess sludge appeared to increase. The separated residual solid was a composite composed of organic and inorganic materials. The proportion of carbon varied from 34.0 to 41.6% depending on reaction conditions. Although 1.89% of hazardous materials were detected, SiO2 (Quartz) was a predominant constituent of the residual solid. X-ray diffraction (XRD) experiments revealed that the residual solid was of a partially amorphous state, suggesting that the residual solids could be easily converted to stable and non harmful substances through a stabilization process. Thus, this technology could be successfully used to control excess sludge and its reuse.

• Journal of Environmental Health Sciences
• /
• v.31 no.1
• /
• pp.86-93
• /
• 2005

Because generally large amount of sludges are generated from the process of sewage and wastewater treatment, the management and controlment of those sludge has become a important issue in many researches. In this dissertation, we conducted the research to see the physico-chemical characteristics of sludges generated from various sources. Moisture of sludges were 81.5% in textile industries, 81.4% in frame metal industries, 80.7% in 1st metal industries. Volatile solid were 22.1% in hide · rubber industries, 21.9% in coke · petroleum industries. Fixed solid were 18.5% and 17.7% in the 1st metal industries and frame metal industries. High heating value by wet base were 1,850 kcal/kg in coke · petroleum industries, 1,220 kcal/kg in hide · rubber industries, but sludges from the 1st metal industries and frame metal industries were impossible to incinerate because most of those sludges were inorganic. The leaching test showed that hazardous materials was detected in nearly every kinds of sludges. Some of sludges from hide · rubber industries and frame metal industries exceeded the leaching criteria and so they were classified as specific wastes. And other sludges generated in sewage treatment plants or other industries was below the leaching criteria.

• Korean Journal of Environmental Agriculture
• /
• v.16 no.3
• /
• pp.220-226
• /
• 1997

To study the possibility of agricultural utilization of the municipal sewage and the industrial wastewater sludges, the chemical properties of soil, the growth response of corn plant and uptake of inorganic nutrients in plant tissues were investigated by application of the composts made of the sludges to the pots at the rate of 2,000kg/10a. The contents of organic matter, T-N, $P_2O_5$ and K in soil were increased by application of the composts. Each heavy metals contents in soil were increased very slightly by application of the composts. The fresh weights of corn plant were increased with $9{\sim}19%\;and\;60{\sim}79%$ at the plot of compost and NPK+composts in comparing with the plot of NPK, respectively. Uptake of N, $P_2O_5,\;K_2O$, CaO and MgO in stem and leaf of corn plant were increased by applications of the composts.

• Journal of Korean Society of Water and Wastewater
• /
• v.23 no.5
• /
• pp.669-678
• /
• 2009

The reduction of excess activated sludge from petrochemical plant was investigated by the electro fenton (E-Fenton) process using electrogenerated hydroxyl radicals which lead to mineralization of activated sludge to $CO_2$, water and inorganic ions. Factors affecting the disintegration efficiency of excess activated sludge in E-Fenton process were examined in terms of five criteria: pH, $H_2O_2/Fe^{2+}$ molar ratio, current density, initial MLSS (mixed liquid suspended solids) concentration, $H_2O_2$ feeding mode. TSS total suspended solid and $TCOD_{cr}$ reduction rate increased with the increasing $H_2O_2/Fe^{2+}$ molar ratio and current density until 42 and $6.7 mA/cm^2$, respectively but further increase of $H_2O_2/Fe^{2+}$ molar ratio and current density would reduce the reduction rate. On the other hand, as expected, increasing pH and initial MLSS concentration of activated sludge decreas TSS and $TCOD_{cr}$ reduction rate. The E-Fenton process was gradually increased during first 30 minutes and then linearly proceed till 120 minutes. The optimal E-Fenton condition showed TSS reduction rate of 62~63% and $TCOD_{cr}$ (total chemical oxygen demand) reduction rate of 55~56%. Molar ratio $H_2O_2/Fe^{2+} = 42$ was determined as optimal E-Fenton condition with initial $Fe^{2+}$ dose of 5.4 mM and current density of $6.7{\sim}13.3 mA/cm^2$, initial MLSS of 7,600 mg/L and pH 2 were chosen as the most efficient E-Fenton condition.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.27 no.6
• /
• pp.690-695
• /
• 1994

Simultaneous removal of phosphorus and nitrogen from wastewater was studied by the anaerobic-aerobic system of activated sludge. In the anaerobic stage, most of the influent glucose was removed and orthophosphate was released, when the nitrate and/or nitrite concentration in the wastewater was almost zero. The amount of the released phosphorus was found to be directly proportional to the amount of the removed glucose. When the ratio of phosphorus to glucose in the influent was less than 0.04, the phosphorus in the wastewater was almost completely removed during the aerobic state. Under the anaerobic condition, activated sludge released phosphate and excess removal of phosphate occurred during the aerobic condition. Namely, the stress received in anaerobic period stimulated the uptake of phosphorus in aerobic period. The amounts of phosphorus release in the anaerobic and uptake in the aerobic stage were less in proportional to the concentration of $NO_x-N$. Further, if the initial ratio of $NO_2-N$/glucose was less than 0.37, the inorganic nitrogen in the influent could be completely removed.

• Resources Recycling
• /
• v.9 no.1
• /
• pp.36-43
• /
• 2000

This study was carried out for treatment and reuse of inorganic sludge from Fenton process at B dyeing wastewater treatment plant. The parameters for pilot-scale treatment system were derived from the results of this study. It was found that $COD_{cl}$ of the treated effluent became lower than 100 mg/l approximately on the optimal reaction condition. 2nd sludge which was generated after redissolving sludge was analyzed, and it showed that reduction ratio of ash in 2nd sludge and total dry sludge weight in comparison with current sludge were 85% and 65%. Also Fe salt in sludge was redissolved about 90~95% of initial Fe by weight. It was estimated almost ￦350,000,000 for sludge reuse process. It was estimated saving of about ￦1,300,000 per day (￦420,000,000 per year) in operating cost based on 30,000 $m^3$/d treatment, which these were about ￦430,000 per day in chemical, ￦1,100,000 per day in sludge transportation and ￦200,000 per day in equipment maintenance. Payback period with interest charge for investment cost was estimated about 10.5 months. Also, net present value (NPV) was ￦792,000,000 and internal rat of return (IRR) was about 110%.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.4 no.1
• /
• pp.53-60
• /
• 1996

This study was carried out to investigate the effects on the growth of soybean and carrot, and these uptake of inorganic components, after the application of sewage sludge disgested anaerobically at wastewater treatment plant for about 25 days. With the application of the sludge, some chemical properties of soil was improved and heavy metals, as Pb, Cd, Cr, As and Hg, in finally harvested crops were not detected. With an increase in the application of the sludge, the uptake of N, P, K, and Ca in carrot was increased and also in the yield of two crops. In related to the quality of carrot, however, application of unmatured sewage sludge showed to deteriorate the visual quality with an irregularity of carrot's surface, despite of the increase of ${\beta}$-carotene concentration with an increased application of the sludge. The results suggest that for a land application of sewage sludge it should be necessarily stabilized by means such as composting.