Toilet per million passengers
The idea of reconstructing airport sewage systems using emergency control tanks.
When developing the concept of engineering support for the Sheremetyevo-2 sector, the specialists of our company did not bypass the modern technology for the reconstruction of existing sewage pumping stations by building a new type of control tank. Flow regulation for transport infrastructure facilities is of great importance, because, according to SNIP, at airports, the coefficient of uneven sewage flow is 3. Experts understand what this leads to. Calculations of the entire system of transportation and disposal are made for peak load. The power of pumps, the diameters of pipelines increase MULTIPLE compared to the average value.
In practice, things get even worse. If the coefficient of unevenness 3 is still far away. And in recent years, at large airports, the work of all departments and services does not stop around the clock. It turns out that the choice of equipment and the calculation of wastewater transportation systems led to a significant "brute force". There is only one way out - smoothing the load. The APP solves this problem.
So, to increase the operational performance of the KNS-5 of Sheremetyevo Airport by 1000 cubic meters. per day i.e. by 30 percent it is enough to simply rebuild the existing emergency tank into an emergency-regulating one. Otherwise, it would be necessary to shift the 8 km long discharge pressure pipelines with an increase in diameter, replace the pumps with an increase in power consumption and an automation system.
"Force on force"
External engineering networks of the office complex of JSC AEROFLOT-RA.
Technological connection of pressure conduits from the projected sewage pumping station to pressure conduits of the main sewage pumping station of JSC Sheremetyevo International Airport (PSS-5).
Our design organization performed a hydraulic calculation of options for connecting the designed sewage pumping station to existing networks and structures.
Thanks to the engineering calculation, the possibility of connecting pressure water conduits d.160 from the office complex being designed by the sewage pumping station with a capacity of 0.1 thousand cubic meters per day was proved. Directly through the connection chamber to existing conduits d.400.
The construction of water conduits from the designed SPS to SPS-5 was canceled, including 1600 m. routes in two pipes and a closed passage through the Klyazma river. Instead, 120 rmp were built. tracks and switching chamber. The switching chamber is also sectional for conduits from the head KNS-5 to the damper well. The design solution proposed to build 4 sectioning chambers to improve the reliability of the water conduits.
The calculation considers options for connecting pressure water conduits from the designed sewage pumping station to conduits from the sewage pumping station-5 at two different points. The first option is to connect at the nearest point. The second is the connection at the dictating point of pressure conduits.
The first connection option is characterized by the minimum cost of construction.
The second option, due to the construction of a switching chamber at the dictating point, increases the operational capacity of KNS-5 by 1000 cubic meters per day. This makes it possible to have a regulatory reserve for water pipelines for KNS-5. That is, in the event of an accident on one of the conduits at any place, the operation of the conduits will always be ensured according to the scheme: half of the route into two conduits / half into one conduit.
As a result of the work carried out, savings in capital investments of about 80% were achieved.
In addition, the reliability of the entire system and its operational performance have been increased.
The paper also shows the prospect of developing the sewerage system of OAO SIA, which provides for the reconstruction of KNS-5 with the construction of an Emergency-Regulating Reservoir. Such a reconstruction can increase the performance of the system by another 1000 cubic meters. per day. The reliability of the work will undoubtedly increase.Operating costs will be reduced by choosing a permanent economical mode of operation of the KNS-5 pumps.
When ordering services for the calculation and design of KNS, we recommend that you pay attention to our service of field supervision. When ordering it, we, as the authors of the project, will monitor compliance with all the requirements of the project by the construction organization
Selection of the brand and number of pumping units
Pumps, equipment and pipelines should be selected depending on the estimated inflow to the sewage pumping station, the physical and chemical properties of wastewater, the height of the lift, and taking into account the characteristics of pumps and pressure pipelines.
Determining the flow of pumps
The maximum flow of the pumping station is taken equal to the largest hourly inflow of wastewater qw, m3/h, or slightly exceeding it.
First, the daily wastewater consumption, m3/day, is determined by the formula
,
where qx is the specific water disposal per 1 inhabitant, l/(person•day);
Nzh is the number of inhabitants, pers.
The average hourly consumption qmidl, m3/h, is determined by:
and the average flow rate q, l/s, is determined by:
where T is the duration of operation of the pumping station during the day, hours. For settlements, T = 24 hours.
According to the average second flow q from the total maximum non-uniformity coefficient kgen.max is taken.
At q=162 l/s kgen.max=1.584.
The maximum hourly consumption q, l/s, is determined by: q=qmidl • kgen.max=1.584•583=924 m3/h.
The maximum flow rate per second is determined by: qmax=q • kgen.max=162 •1.584=256.6 l/s.
Rounding of the calculated values of daily costs must be performed to tens, hourly costs to units, second costs to tenths.
The maximum second flow rate qmax of sewage is supplied by a gravity collector, the hydraulic parameters of which are determined from .
At qmax=256.6 l/s, the pipeline diameter is D=800 mm, filling N/D = 0.6, hydraulic slope i = 0.001.
Determination of pump head
The required head Htr, m, (Fig. 2.1), the value of which is necessary for the selection of pumps, is determined by the formula:
Ntr \u003d Ng + hwater + hn.s. + hsv, (2.7)
where Hg is the geometric height of the wastewater rise; equal to the difference between the marks of the maximum water level in the receiving chamber of the treatment facilities Z2 and the average water level in the receiving tank of the pumping stations Z1. Since in the initial data there is no exact mark for the supply of wastewater to the treatment plant, we tentatively take Z2 2 m above the ground level at the location of the receiving chamber of the treatment plant. The mark Z1 is 1 m below the mark of the inlet collector tray to the receiving tank of the pump station.
Then:
Z2=145.000+2.0=147.000 m;
Z1=136.000-1.0=135.000 m;
Hgeom=147.000-135.000=12.0 m.
hwater - pressure loss in the pressure pipeline, m:
hwater=1.1•i •L,
where i is the hydraulic slope (pressure loss per unit length of the pipeline);
L is the length of the pressure pipeline from the sewage pumping station to the sewage treatment plant, m.
In the project, we accept 2 lines of pressure pipelines from the sewage pumping station to the WWTP. According to the assignment, the length of each thread is L = 500 m. Then each pipeline is calculated for 50% wastewater supply q1, l/s; and when one line of the pipeline is disconnected in accordance with the requirements, the second line must pass all 100% of the wastewater flow rate qmax, l / s.
When selecting the diameter D, mm, the corrected speed V, m/s, and the hydraulic slope i, it is necessary to fulfill the requirements based on the allowable (non-silting) speeds.
For wastewater flow rate q1=128.3 l/s, we select: a pipeline made of electric-welded pipes with a diameter (GOST 10704-91 and GOST 8696-74) D=400 mm, speed v=0.96 m/s and hydraulic slope i = 0 .0032 ;
When disconnecting (accident) one thread, when
qmax=256.6 l/s and D=400 mm Vav=1.92 m/s, i=0.0125.
Then
hwater=1.1 •0.0032 •500=1.78 m.
havod=1.1 • 0.0125 •500=6.88 m.
hns - pressure loss along the length and local in the internal suction and pressure lines of the station. We preliminarily accept hns = 2 m. In the future, they are specified;
1gsv - free head when sewage is poured out of the pipe; L„ \u003d 1.0 m.
Нtr=12.0+1.78+2.0+1.0=16.78 m.
Natr \u003d 12.0 + 6.88 + 2.0 + 1.0 \u003d 21.88 m.
Equipment and design features of the sewage pumping station
The design features of the sewage pumping station are determined by the composition of the pumped wastewater, which contains a large number of various inclusions. The use of submersible pumping units significantly reduces the cost of operating the sewage pumping station. Grids are installed in the receiving tank of the station, in which large debris coming with drains is retained.The size of the openings of the gratings depends on the power of the pumping units. At the inlet of the sewage pumping station, a waste bin is installed on the supply pipeline.
Periodically, the basket is lifted to the surface and cleaned. The main valves are located on the supply pipeline to the sewage pumping station. To carry out repair or maintenance work on pressure pipelines, gate valves, gate valves or check valves are installed. To perform the installation or dismantling of pumping units and lifting gratings and other equipment to the surface, manual hoists with a lifting capacity of up to one ton are used.
The control system ensures the functioning of the KNS in automatic mode. The use of automatic control ensures uniform wear of the pumps, changes the priority of pumping units from working to standby and vice versa after each start. In case of failure of the working pump, an TROUBLE signal is generated and the backup unit is automatically started.
With a large flow of wastewater (the level of wastewater inside the sewage pumping station does not decrease), the control system, in parallel with the main one, connects the standby unit and turns on the alarm. The emergency operation mode will be active until the lower drain level sensor is turned on.
The automatic control unit in its circuit has a switch for switching to backup power. An audible and visual alarm is provided to notify of an emergency situation. The control board is housed in a protective metal casing.
The calculation of a sewer pumping station contains all the stages of creating a sewage pumping station, including installation work. The installation of the sewage pumping station is carried out in several stages: installation of the station body in the pit, installation of pressure and gravity collectors, connection of the power cable.
Determination of the capacity of the receiving tank and the choice of equipment
Determining the capacity of the receiving tank
The capacity of the receiving tank is determined depending on the mode of inflow and pumping of sewage and the permissible number of switching on of electrical equipment within 1 hour.
The volume of the receiving tank, m3, must not be less than the volume equal to the five-minute maximum flow of one of the Q1 pumps, m3/h:
With the estimated capacity of the receiving tank and the minimum and average inflow of wastewater into the receiving tank, it is necessary to determine the number of switching on of pumping units within 1 hour.
The maximum pump flow will be Q1=462 m3/h, and the inflow will be taken equal to half the pump flow Qpr=231 m3/h.
Point A is plotted on the graph, corresponding to the hourly (i=60 min) pump flow Q1=462 m3/h. Connecting point A with the origin, we get line 1 - an integral graph of the maximum possible pumping out of the pump.
By connecting point B corresponding to the selected estimated hourly inflow, we get line 2 - an integral graph of the estimated inflow of wastewater.
If we assume that at the beginning of the hour the receiving tank was empty and the pump was not working, then the point a determines the moment of complete filling of the tank.
At this moment, the pump turns on, which pumps out both the liquid accumulated in the tank and the liquid arriving during this period of time.
The pump operation schedule for this period of time is obtained by drawing from point b a line parallel to line 1 until the intersection of line 2. At this point, the tank becomes completely empty again and the pump is turned off. The moment of inclusion (points e, h) and the integral graph of pumping wastewater into the second and third inclusions (lines de and zk) are constructed similarly.
It can be seen from the graph that the pump will turn on three times per hour, that is, the restriction on the number of pumping aggregates for 1 hour has been met.
According to the standard design, the capacity of the receiving tank is 230 m3, which corresponds to a 30-minute performance of one pump SM 250-200-400a/6.
The bottom of the receiving tank has a slope z=0,l to the pit, in which the funnels of the suction pipelines are located.
The receiving tank is equipped with a device for stirring up and washing off the sediment.
The supply of water for stirring is regulated by a valve.
To flush the oil from the walls and bottom of the tank, a watering tap is provided, equipped with a rubber sleeve with a textile frame.
Water is supplied to the watering tap from the hydraulic sealing system for the stuffing boxes of the main pumps SM 250-200-400a/6.
The descent into the receiving tank is carried out through a special hatch along the running brackets.
Choice of grating type
Grids are installed in the receiving tank to hold large wastes.
Waste volume Wot, m3/day, removed from the screens, is determined by the formula:
where aotb is the amount of waste removed from the grates, per 1 person, l / year, depending on the width of the gaps B, mm, in the grates. At B = 16 mm aotb = 8 l / year-person (Table 1.6);
Nx is the number of inhabitants in the settlement, people.
Grids with mechanized rakes are accepted.
The grating sizes are selected according to the required area of the living section of the working part of the gratings, m2:
where qmax is the maximum inflow of wastewater, l / s;
Vp is the velocity of the fluid in the gaps of the grating m/s;
Vp=0.9 m/s,
One working grid is accepted.
With mechanized gratings, crushers are installed to grind the waste and dump them into a receiving tank.
The amount of waste removed from the grates Gotb, kg / day:
Gotb= gob•Wotb=750•1.54=1154 kg/day
where otb is the specific gravity of waste, kg / m3, otb = 750 kg / m3.
In the standard project 902-1-142.88 *, two mechanized unified grates MG 9T (1 working, 1 reserve) with a maximum throughput of 33,000 m3 / day and a D-Z hammer crusher for crushing waste with a capacity of 300-600 kg / h are installed in the grating room.
Specifications are presented in table. 2.6:
Table 2.6 Technical characteristics of the grating MG 9T:
|
brand |
Channel dimensions in front of the grate, mm |
Opening width, mm |
Water throughput, m3/day |
Lattice width at the floor B1, mm |
Weight, kg |
|
|
V |
H |
|||||
|
MG 9T |
1000 |
1200 |
16 |
33000 |
1425,0 |
1320 |
The flushing of waste to the crusher is carried out with water from the pressure pipeline of the pumping station. The crushed waste is discharged into a receiving tank.
