What does detention time mean?
Detention Time. Detention time is a measure of how long a given molecule of water resides within a pond before being discharged.
What is detention time in a coagulated tank?
Stated another way, the detention time is the length of time theoretically required for the coagulated water to flow through the tank / basin.
How do you calculate detention time for a sedimentation basin?
Volume, gal = 0.785 x (Diameter)2 x Depth, ft x (7.48 gal/ft3) Detention time for clarifiers, or sedimentation basins, varies from 1 to 3 hours and can be determined from one of the following equations: A sedimentation basin has a volume of 142,000 gallons. If the flow to the tank is 133,00 gph, what is the detention time in the basin, in hours?
How do you calculate unit process detention times?
When calculating unit process detention times, we are calculating the length of time it takes the water to flow through that unit process. To calculate the detention period of a tank, the volume of the tank, must first be obtained.
What is meant by detention time?
The actual or theoretical (calculated) time required for water to fill a tank at a given flow; pass through a tank at a given flow; or remain in a settling basin, flocculating basin, rapid-mix chamber, or storage tank.
How do you calculate detention time?
The simplest way to calculate detention time is to divide the volume of the container by the flow rate into the container. The theoretical detention time of a container is the same as the amount of time it would take to fill the container if it were empty.
What is the difference between retention time and detention time?
Detention and retention both refer to storing rain water on-site during a storm event, when the risk of flooding is highest. The difference is that when water is detained, it is slowly released into a stream or river and leaves the site. When water is retained, it is not intended to leave the site.
How do you calculate detention time for grit chamber?
The Detention Time when Volume of Each Grit Chamber is Given calculates the length of time water is retained in a grit chsmber is calculated using Detention time = (Volume*7.48*24*60)/Peak flow rate.
Why is detention time important?
Detention time is an important concept to understand because it is used in many different water treatment processes. It is used during the processes of mixing, coagulation/flocculation, and sedimentation.
What do you mean by detention time in a treatment basin?
Detention Time is the amount of time it takes for a molecule of water to travel a certain distance. In a sedimentation basin it is the time it takes for a particle to travel across the basin. Water treatment operators calculate detention times for settling basins, flocculation basins, or rapid mixing chambers.
What is difference between detention and retention?
A good rule of thumb for distinguishing these types of systems is to remember that detention is temporary but retention is intended to be permanent.
How is mean cell residence time calculated?
The mean cell residence time of an activated sludge process can be calculated by dividing the pounds of suspended solids or MLSS in the activated sludge system by the pounds per day of suspended solids leaving the activated sludge system (Equation II.
Why are retention times not a good indicator of the sample identity?
However, retention time is not a reliable factor to determine the identity of a compound. If two samples do not have equal retention times, those samples are not the same substance. However, identical retention times for two samples only indicate a possibility that the samples are the same substance.
What is detention time for truck drivers?
Driver Detention occurs when the shipper impedes the truck driver from loading or unloading through no fault of the carrier. The acceptable industry standard is two hours, although rules tariffs (carrier rules that govern their operation and their charges) allow up to four hours.
What is detention time of septic tank?
24 to 48 hoursAs per IS code specifications the detention period of a septic tank is 24 to 48 hours. A septic tank may be defined as a primary sedimentation tank with a longer detention period i.e. 12 to 36 hours and with extra provision for digestion of the settled sludge.
How do you calculate water retention time?
The average amount of time that liquid and soluble compounds stay in a reactor or tank. It is calculated by dividing the volume of a reactor (e.g. m3) by the influent flow rate (e.t. m3/day).
How do you calculate column residence time?
Residence Time Calculation is made from the following formula: Volumetric flow rate (L/h) = (flow velocity (cm/h) x (column crossectional area (cm2) / 1000).
How long does a clarifier stay in the sediment?
Detention time for clarifiers, or sedimentation basins, varies from 1 to 3 hours and can be determined from one of the following equations:
What is sedimentation in water?
Sedimentation is the process of allowing particles in suspension in water to settle out of the suspension under the effect of gravity. The particles that settle out from the suspension become sediment, and is known as sludge. In water treatment, sedimentation might be used to reduce the concentration of particles in suspension before the application of coagulation, to reduce the amount of coagulating chemicals needed, or after coagulation, possibly, flocculation. When sedimentation is applied after coagulation, its purpose is to reduce the concentration of solids in suspension so that filtration can function effectively.
How deep is a sedimentation basin?
A sedimentation basin is 35 ft wide by 75 ft long and contains water to a depth of 12.5 ft. What is the volume of water in the basin, in gallons?
What is detention time?
Detention time is a measure of how long a given molecule of water resides within a pond before being discharged. HydroCAD provides two techniques for evaluating the detention time, as described below. These values are automatically calculated for all pond routings, and the results are displayed in the pond summary report.
How to increase detention time in pond?
In general, detention time can be increased by using a smaller outlet device with the appropriate amount of storage. In some cases (such as low-volume water quality events), this may require an unreasonably small outlet, which is prone to blockage. A common solution is to raise the outlet above the bottom of the pond, and provide enough storage capacity so that the water quality event can be fully retained, thereby providing an infinite detention time. The draw-down of the pond can then be allowed to occur over an extended period, often by infiltration. In some cases, a "wet pond" may also provide a suitable detention-time, based on the first-in-first-out criteria used by the plug flow method, as described above.
What is the best method to determine the average detention time of a pond?
A better approach is the plug flow method , which can be used to determine the theoretical average detention time within any pond. In essence, this technique indicates the average length of time that a given molecule of water resides within the pond.
Is detention time a routing procedure?
Note: Detention time calculations are not routing procedures. They are a separate analysis that is performed after the actual hydrograph routing has been completed by the specified routing procedure.
What is the difference between detention and demurrage?
Difference Between Detention and Demurrage. One term that you may often hear in association to detention charges is demurrage charges which may also be referred to as per diem charges. Some people may even confuse the two thinking that they are the same thing.
How Do You Calculate Your Detention Rate?
To know your detention rate, you first need to know your operating cost. If you are a trucker and would like to learn more on the operating cost there is a great article here to help you with just that. Your operating cost covers every expense required to run your company: fuel, maintenance, tires, permits, and salaries all contribute to this cost. To move forward from this and figure out what your detention rate should be from your operating cost would be to break it down further and find out what your operating cost is per hour. From here you will have a much better idea of what a detention time is costing your business to know what to negotiate for a fee during that time.
What is detention in trucking?
Any time spent outside of the allotted two hours is detention. The detention is used to offset the cost of a truck being detained at a shipper or receiver.
Do you need to figure out your detention rate?
If this is the case, you will not need to figure out your detention rate . However, if you are not using a broker, your detention rate may be good information to know. To get started you need to know your operating cost ...
Can you negotiate detention with a shipper?
NOTE: Negotiating detention with a broker or shipper needs to happen while you are negotiating your freight rate. In addition, make sure to get the final, negotiated amount in writing, or you run the risk of not getting paid. Stay on top of your monthly expenses.