What are the different types of weirs?
What are the different types of weirs?
Types of Weirs:
- Types of Weirs based on Shape of the Opening. Rectangular weir. Triangular weir. Trapezoidal weir.
- Types of Weirs based on Shape of the Crest. Sharp-crested weir. Broad- crested weir. Narrow-crested weir. Ogee-shaped weir.
- Types of weirs based on Effect of the sides on the emerging nappe.
How is Weir calculated?
- Q = 0.35 x B x (2g)0.5 x H1.5
- where;
- Q = water flow rate, m3/sec.
- B = width of the weir, metres.
- g = gravitational constant, 9.81.
- H = h x (V2)/2g where, h = height of the water over the weir at the discharge edge of the weir, m.
- V = velocity of the stream across the weir crest, m/sec.
What are weirs used for?
Weirs are fixed barriers across a river or stream that force water to flow over their tops, where the height of the water above the weir can be used to calculate flow.
What is flow over weirs?
The depth of water above the base of a weir is related to the flow rate through it; therefore, the weir can be used as a flow measuring device. The relationships of flow over weirs can be obtained by applying the energy equation from a point well upstream of the weir to a point just above the weir crest.
What is Weir loading rate?
Weir loading rate is the flow rate of the clarifier effluent per the length of the overflow weir. It is argued that if the weir loading rates exceed the recommended values, the velocity of currents approaching the weirs may be such that excessive solids are carried over the weir.
What is solid loading rate?
Solids Loading Rate (SLR) SLR is defined as the mass of solids applied per unit clarifier surface area per unit time and is typically expressed as pounds per day per square foot (lbs/d. sf).
How is weir overflow rate calculated?
The overflow rate (also known as the surface loading or the surface overflow rate) is equal to the settling velocity of the smallest particle which the basin will remove. Surface loading is calculated by dividing the flow by the surface area of the tank. Overflow rate should usually be less than 1,000 gal/day-ft.
What is surface loading rate?
The surface loading rate is the number of gallons of wastewater passing over 1 ft2 of tank per day. Plant designs generally use a surface loading rate of 300 to 1200 gpd/ft2. Other terms used synonymously with surface loading rate are surface settling rate and surface overflow rate.
What does surface loading mean?
1. (Aëronautics) The weight supported per square unit of surface; the quotient obtained by dividing the gross weight, in pounds, of a fully loaded flying machine, by the total area, in square feet, of its supporting surface.
What is BOD load?
BOD (or COD) load: Units: kg/day Biological wastewater treatment plants are designed and operated on the basis of the oxygen demand (BOD or COD) received and removed. The concentration of BOD (in mg/l) in the influent can be used to calculate the total BOD load per day being treated.
What is hydraulic loading rate?
Hydraulic loading rate means the rate at which wastes or wastewaters are discharged to a land disposal or land treatment system, expressed in volume per unit area per unit time or depth of water per unit area per unit.
How is load rate calculated?
You can calculate loading rates with a few basic steps. Calculate the hydraulic loading rate with the formula: Hydraulic loading rate = Design flow (gal/day) / Area (feet ^2). Design flow is the volume of waste water per day.
What is a loading rate?
Loading rate is the speed at which you apply forces to the body. The steeper slope (top graph) means that the forces applied to the runner occur quicker than that of the forces applied to the less steep slope (bottom).
What is hydraulic retention time?
The Hydraulic retention time (HRT) or t (tau) is a measure of the average length of time that a soluable compound remains in a constructed bioreactor. The volume of the aeration tank divided by the influent flowrate is τ (tau), the hyraulic retention time.
What is retention time?
Retention time is the time that a solute spends in a column or it can be defined as the time spent in the stationary and mobile phases. The longer retention time depends on the interaction of the analyte with the stationary phase. The stronger the interaction, the more will be the interaction time.
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 determine sludge age?
The sludge age of an activated sludge process can be calculated by dividing the pounds of suspended solids or MLSS in the aeration tanks by the pounds of suspended solids that enter the aeration tanks (Equation I.
How do you calculate sludge?
Sludge volume index ( SVI ) is calculated by dividing the settleability by the MLSS concentration. The SVI is always expressed in mL/g.
What is difference between MLSS and Mlvss?
MLVSS or MLSS Biological solids are measured in a lab procedure to determine the weight of solids. The difference is the MLSS is total solids weight and MLVSS is the volatile fraction of the total solids (usually just biological solids – but can also include fibers and other organic influent solids).
Why is sludge age important?
Abstract. The sludge age is the most fundamental and important parameter in the design, operation and control of biological nutrient removal (BNR) activated sludge (AS) systems. The easiest and most practical way to control sludge age is with hydraulic control by wasting a defined proportion of the reactor volume daily …
How do you increase sludge age?
Normally, a bright white foam will occur on the aeration section of the plant, looking similar to soap suds. All of the sludge from the clarifier should be returned to the aeration section of the plant to raise the sludge age as soon as possible.
How do I control bulk sludge?
Control of low F/M bulking is by reducing the aeration basin MLSS concentration and increasing the F/M (manipulating the “M” component). Lowering the MLSS concentration may not be suitable for many plants as this may cause the loss of nitrification and increase waste sludge production.
What causes bulking sludge?
Abstract. Sludge bulking is the most common solids settling problem in wastewater treatment plants, which is caused by the excessive growth of filamentous bacteria extending outside the flocs, resulting in decreasing the wastewater treatment efficiency and deteriorating the water quality in the effluent.
Why does sludge float?
Denitrification – small nitrogen gas bubbles float the sludge in the clarifier creating floating sludge chunks with small bubbles entrapped. Fats, Oils & Grease – simply put, FOG floats on water. This is often caused by nutrient deficiencies (normally low phosphate) in industrial waters.
How can you improve settling in activated sludge?
Excess organic load can be remedied by reducing the waste-activated sludge rate by an amount less than 10 percent per day, to return to proper loading parameters and increase the returned activated sludge rates. About a 30 percent level of settled solids in the clarifier should be established and maintained.
What is the purpose of the return sludge step in the activated sludge process?
The purpose of Return Activated Sludge (RAS) is to prevent loss of microorganisms from the aeration tank and maintain an adequate population for treatment of the wastewater. As microbes metabolize their substrate, they grow and multiply in number.
