• Journal of Korean Society on Water Environment
• /
• v.31 no.2
• /
• pp.196-208
• /
• 2015

This study analyzed the characteristics of sewer flow and its water quality, and investigated changes in the characteristics in three areas where the sewer rehabilitation projects have been carried out. In S1 area, the patterns of the flow became regular and the range of the fluctuation decreased after the sewer rehabilitation. The flow and its BOD concentration increased. The infiltration/inflow and exfiltration showed clear distinction before and after the sewer rehabilitation in this area. In S2 area, the patterns and the range of the fluctuation of the flow made no differences before and after the sewer rehabilitation. The flow decreased slightly and its BOD concentration increased considerably after the sewer rehabilitation. Big decrement in stormwater inflow but small in exfiltration appeared in this area. In S3 area, the patterns and the range of the fluctuation of the flow made no differences before and after the sewer rehabilitation. The flow decreased slightly and its BOD concentration increased in a small rate in this area.

• Journal of Korean Society of Water and Wastewater
• /
• v.28 no.6
• /
• pp.647-655
• /
• 2014

To perform long-term sewer monitoring, It is important to understand the nature of the wastewater flow that occurs at the point on early stage of the monitor and to prevent in advance a problem which may caused. We can infer the flow properties and external factors by analyzing the scatter graph obtained from the measured data flow rate monitoring data since an field external factor affecting the sewage flow is reflected in the flow rate monitoring data. In this study, Selecting the three points having various external factors, and we Inferred the sewer flow characteristics from depth-velocity scatter graph and determined the analysis equation for the dry-weather flow rate data. At the'point 1' expected non-pressure flow, we were able to see the drawdown effect caused by the free fall in the manhole section. At the'point 2', existed weir and sediments, there was backwater effect caused by them, and each of size calculated from the scatter graph analysis were 400 mm and 130 mm. At the'Point 3', there is specific flow pattern that is coming from flood wave propagation generated by the pump station at upstream. In common, adequate equations to explain the dry weather flow data are flume equation and modified manning equation(SS method), and the equations had compatibility for explaining the data because all of $R^2$ values are over 0.95.

• Journal of Korean Society of Water and Wastewater
• /
• v.25 no.2
• /
• pp.185-192
• /
• 2011

Pearson's correlation was used to determine relations between infiltration and affecting factors using flow monitoring data measured in 24 areas with different characteristics. Factors showed relatively high correlations than others were indexed to determine infiltration rates of the study area. Among 8 factors(service area, sewer length, sewer diameter, multiplier of sewer length and diameter, number of manholes, population, number of properties, number of households) tested, the multiplier of sewer length and diameter, the number of population and the number of household in each service area indicated higher correlation coefficient(>0.8) than others. The goodness of fitness of linear regressions between infiltration and the factors followed the order: sewer length and diameter(0.68)> population(0.65)> number of household(0.60). Infiltration rates calculated by the multiplier of sewer length and diameter, the number of population and the number of household in each service area were 0.046~1.0396 $m^{3}/d{\cdot}mm-km$, 0.0917~1.7355 $m^{3}/capita{\cdot}d$, 0.196~4.529 $m^{3}/household {\cdot}d$ respectively. After sewerage rehabilitation work of the area, the infiltration rates calculated by above factors with high correlations are expected to be used for comparing effectiveness of the work once they are estimated under the same flow measuring conditions.

• Journal of Korean Society of Water and Wastewater
• /
• v.25 no.6
• /
• pp.877-884
• /
• 2011

Although peak loading coefficient is one of critical design factors for sewer works, its detailed affecting factors were not analyzed because of limited data availability. This study analyzed the affecting factors on peak loading coefficient with plenty data obtained from several newly constructed sewer works. Simple and multiple regression analysis methods were adopted to analyze the relationships of each variable with or without data filtering. Drainage population, drainage area, population density, and daily sewage flow per person showed very weak relationships under diverse characteristics of cities. However, daily sewage flow per person showed stronger relationships with peak loading when daily sewage flow per person was splitted into two ranges. Population density (i.e., drainage population divided by drainage area) and daily sewage flow per person considerably were related with peak loading coefficient when daily sewage flow per person is less than about 400 Lpcd.

• Journal of Korean Society of Water and Wastewater
• /
• v.19 no.5
• /
• pp.557-564
• /
• 2005

The objective of this study is to evaluate a criteria of intercepting capacity and a reduction goal of overflow pollution load in combined sewer system. In the current criteria of intercepting capacity in the domestic sewage facility standard, it is known that three times of peak sewage (Q) in dry period or runoff flow by 2mm/hr is not appropriate since the intercepted flow is estimated by runoff and show different result even in the same watershed. Though a reduction goal of overflow pollution load can be determined from 1) same level of storm-water runoff pollution load in separated storm sewer, 2) less than 5% sewage load in dry weather period, by the domestic sewage facility standard, the simulated results from storm-water model show large differences between two criteria. While it is predicted that sewage pollution load standard three time larger than separated storm sewer standard in high population density and urbanized area, it is shown that separate storm sewer standard larger than sewage pollution load standard in middle population density and developing area. Accordingly, it is proposed that more reasonable intercepting flow and reduction goal of overflows pollution load should be established to minimize discharging pollution load in combined sewer systems. For the purpose, a resonable standard has to be amended by pollution load balance considering the characteristics of a watershed for generation, collection, treatment, and discharging flow.

• Journal of Korean Society of Water and Wastewater
• /
• v.19 no.3
• /
• pp.348-356
• /
• 2005

Water quality sampling surveys and continuous measurement of flow were conducted to identify wastewater flow characteristics for representative catchment of O and M treatment basins in A city. For HS-1 station representing commercial area, wastewater flow rises in the beginning of office-working hours, moves up and down within narrow range, and lasts till office-leaving hour, and falls gradually reflecting worker's returning home. However, in HS-2 station representing residential area, wastewater flow has two peaks, which are before office-going hour and after office-leaving hour. In residential area, the flow rate of weekends is higher than that of weekdays because it reflects population, being not contributed to generate wastewater during the working hours of weekdays, stay home and produce wastewater for weekends period. To determine the priority for rehabilitation of sewer system, infiltration rate was computed by dividing infiltration flow by mean diameter and total length of sewer, and HS-1 station ranked the first.

• Journal of Korean Society of Water and Wastewater
• /
• v.23 no.6
• /
• pp.789-797
• /
• 2009

The flow in the beginning lateral sewer can be characterized as intermittent and unsteady, and a moment maximum flow energy is required to transport fecal solids in the sewer. It is thus difficult to design to satisfy a minimum velocity criteria (0.6m/s), because of the substantially lower discharge in the beginning lateral sewer. This study is the result of a field survey, and aims to determine a design criteria for the minimum slope to prevent sediment in a lateral sewer. The survey performed on the two flat small catchments in Goyang-si consisting of D400mm hume-pipe, aimed to understand the manner in which the scope of a sewer slope has an effect on sediment in the beginning lateral sewer. The survey showed that the sewer slope below 3‰ had sedimentation of 88.7%, while the sewer slope of 3~6‰ had sedimentation of 47.8%. In addition, the minimum design slope was estimated to refer to the result of hydraulic experiments from Public Works Research Institute in Japan. Analysis showed that the D400mm hume pipe should be installed with a slope of 6.5‰ to prevent sediment in the beginning lateral sewer. For future installations, the study results showed that a D300mm plastic pipe requires a minimum slope of 3.5‰, and a D250mm plastic pipe requires a minimum slope of 3.3‰ in the beginning lateral sewer.

• Journal of Convergence for Information Technology
• /
• v.10 no.7
• /
• pp.153-159
• /
• 2020

In order to find out the condition of flow in sewer pipes, this study investigated the characteristics of tractive force of sewage flow estimated using actual measured values of water level, velocity, and flowrate in sewers located at uppermost portion in a treatment area during dry weather periods. When the scene of sewage flow was taken by CCTV after cohesive and non-cohesive solids (tofu and sand) were put on the sewer invert, it was found that the solids could be flushed without significant interruption. In sewer with slope of 0.00319, the frequency exceeding the minimum tractive force of sewage during a weekday was zero, while it was 10 per day with slope of 0.00603. During the week of the field observation, the event to exceed the minimum tractive force occurred once, suggesting that sewer odor would potentially increase. Maximum tractive force in sewer with steep slope was 2.9-3.1 N/㎡, but with gentle slope it decreased to 1.6-1.7N/㎡. It was also observed that the interval of time maintained below the criterion of minimum tractive force increased, during weekends compared to weekdays and for the sewage including non-cohesive particles which could enter combined sewers during a storm period. This study found that the sewer sediments formed by direct feces input into sewers, through sewer pipes which were designed meeting the standard sewer design criteria, could be flushed without staying as deposited solids state for a long time.

• Journal of Korean Society of Water and Wastewater
• /
• v.18 no.3
• /
• pp.320-330
• /
• 2004

Most of domestic city is served combined sewer system among various sewer system like as separate sanitary, combined sewer system and storm sewers. During the wet weather, sewer and rainfall have been overflowed because it is over capacity of the combined sewer system; that is called combined sewer overflows(CSOs) This research was carried out to investigate runoff characteristics of combined sewer and to evaluate the effective CSOs volume in Hong-Chun gun. During wet weather, SS load of first rainfall at H-1, H-2, and H-3 were 600kg/event, 370kg/event, and 289kg/event, respectively. 55 load of second rainfall were 216kg/event, 113kg/event, and 37.2kg/event. When the first rainfall, event mean concentrations(EMCs) at each site were 702mg/L, 816mgjL and 861.5mg/L. The second rainfall's event mean concentrations(EMCs) were 99.9gm/L, 161.9mg/L, 103.6mg/L. Rrst flush coefficient b at each site were 0.237,0.166, and 0.151. When the first rainfall, the flow containing 80% of pollutant mass of CSOs at each site were 0.55, 0.23, 0.48 in first rainfall, respectively. The case of second rainfall were 0.79, 0.83, 0.81. Most of all, characteristics of rainfall like as analysis of first-flush, CSOs volume, pollutant loadings is investigated to decide intercepted volume for control of CSOs.

• Journal of Korean Society on Water Environment
• /
• v.36 no.5
• /
• pp.423-430
• /
• 2020

To improve the low treatment efficiency of sewage treatment plants, the separated sewer system must be maintained to provide an adequate flow rate and quality of the sewage under the effect of inflow. In this study, data from five locations of Namsuk, Dukgok1, Dukgok2, Kanggu, and Opo were used to conservatively calculate the inflow water volume. The sewer flow and rainfall data were collected in 2017. The factors in the standard method used to calculate the inflow of the combined sewer pipes including "rainy days", "rainfall impact period", and "period for basal sewer" were defined as 3 mm/day, continuous rain for two days, and two weeks prior to the inflow generation, respectively. "Rainy days", "rainfall impact period", and "period for basal sewer" were conservatively adjusted to 5 mm/day, continuous rain for five days, and three weeks prior to the inflow generation, respectively. As a results of the adjustment, the linearity (r²) was improved except for in Dukgok1. This implies that the conservative adjustment made in this study could improve the management quality of sewer pipes. Also, the linear correlation coefficient (a_i) between inflow and rainfall showed a large difference between the target locations, which can be another monitoring factor affecting the quality of sewer pipes. To improve the correlation based on the individual characteristics of the locations in Korea, the automatic algorithm for the inflow calculation should be developed by innovative intellectual technologies for application to the entire national area.