Benopolis Drinking Treatment Plant Plan
- Ben Quattlebaum
- Dec 15, 2018
- 16 min read
Table of Contents
Page
Table of Contents…....…………………………………………………………………………….1
List of Figures…………..………………………………………………………………………….2
1.0 Introduction…………………………………………………………………………………...3
1.1 Benopolis History………………………………………………………………………..…….3
1.2 Our Goal………………………………………………………………………………..……...3
1.3 Objective…………………………………………………………………………………..…..4
1.4 Public Outreach……………………………………………………………………………......4
2.0 Background…………………………………………………………………………………....5
2.1 Regulations for Drinking Water Treatment…………………………………………………...5
2.2 Drinking Water Treatment Plant Capacity….………………………………………………....5
2.3 Proposed Location of Drinking Water Treatment Facility..…………………………………...7
3.0 Design………………………………………………………………………………………….8
3.1.1 Surface Water Process Overview………….………………………………………………...9
3.1.2 Water Collection…………………………………………………………………………...10
3.1.3 Pretreatment and Coagulants……………………………………………………..............10
3.1.4 Rapid Mix…………………………………………………………………………..............11
3.1.5 Coagulation and Flocculation Chamber…………………………………………………....11
3.1.6 Sedimentation Basin……………………………………………………………………….12
3.1.7 Rapid Sand Filtration…………………………………………………………………….....12
3.1.8 Post Treatment…………………………………………………………………………….13
3.2.1 Groundwater Process Overview…………………………………………………………...13
3.2.2 Aeration……………………………………………………………………………………14
3.2.3 Lime Addition……………………………………………………………………………....14
4.0 Summary……………………………………………………………………………………..14
4.1 Overview……………………………………………………………………………..............14
4.2 Public Meeting……………………………………………………………………………….14
References……………………………………………………………………………………….15
Images…………………………………………………………………………………………....15
Appendix I (Calculations)..............................................................................................................16
List of Figures
Page
Figure 1: Current and Projected Population of Benopolis……………………………………….. 6
Figure 2: Total Water Usage in Benopolis Per Year……………………………………………….7
Figure 3: Map of Benopolis With Proposed Plant Location………….…………………………....8
Figure 4: Brief Overview of Surface Water Treatment Process…………………………………...9
Figure 5: Formation of Floc Through Coagulation……………………………………………….10
Figure 6: Diagram of Flocculation Basin………………………………………………………....11
Figure 7: Diagram of Rapid Sand Filtration……………………………………………………....12
1.0 Introduction
1.1 Benopolis History
Benopolis, CA once had a steadily increasing population of over 28,000 people, with its economy fueled by the Exxon Mobile oil refinery within its limits. The city was located along the Carquinez Strait, which flows into the Pacific Ocean after passing San Francisco. It offered public hiking and biking trails and public access to the bay for recreational activities such as sailing and swimming.
The Exxon oil refinery turned out to be the drastic end of Benopolis, however, as heavy flooding during the spring of 2015 caused enough damage to some of Exxon’s oil containers to create a massive spill. Thousands of gallons of crude oil leaked from the containers and mixed with the floodwater, contaminating a majority of the city’s surface water, including a large portion of the bay around it. While Exxon was legally obligated to fund efforts to clean the contaminated land and water, it would be nearly three years until the city was back to the habitable state it once was. Because the drinking water treatment plant was unable to handle the new levels of toxicity in the city’s water supply, and due to other obvious public health concerns, everyone deserted the town. The only visitors to the city besides the Exxon funded clean up crews were occasional vandals and thieves, who over the clean-up process continued to damage public facilities to the point that they needed to be rebuilt from the ground up.
1.2 Our Goal
The Quattlebaum Engineering Company was started in 1997 and places its core values in the ideas of closed-loop systems, resilience, and design for disassembly. These principles of green engineering represent limiting waste while maximizing efficiency in terms of materials, energy, and space overall. The catastrophe that Benopolis has faced gives us an opportunity to start essentially from scratch, and implementing a system that will not only last, but leave little to no footprint behind once the system is no longer needed.
Of our goals, designing closed-loop systems is by far our most ambitious, especially in terms of gaining public support. While this is merely the design plan for the drinking water treatment plant, the Quattlebaum Engineering Co. has been contracted to design the wastewater treatment plant as well as the solid waste management system in Benopolis. That gives us opportunities to responsibly deal with the waste that each of these facilities will produce. For example, while this is generally unpopular regarding public opinion, reclaiming wastewater to be used as drinking water has been proven to be equally as clean for consumption and wastes less of the earth’s freshwater reserves. This, while it may be more expensive to implement, will end up reducing a lot of the waste involved in disposing of wastewater and gathering freshwater.
Resilience is another important concept that the Quattlebaum Engineering Co. focuses on. It would create an absurd amount of unneeded waste for this plant to be shut down in 25 years or so and replaced with a new, larger one. Therefore, we are planning with space in mind for expansions for each and every step of the drinking water treatment process. The plot of land we have recommended was once a massive parking lot, so it is very level and easily buildable on, making expansion and adapting extremely easy.
Design for disassembly is my favorite aspect of the Quattlebaum Engineering Company’s philosophy. Many materials of our plant are connected via interlocking, temporary connections. For example, our flocculation chamber’s “corridors” can be easily slid out of place for cleaning or replacement, and our walkways above the system are connected in a system of “puzzle pieces”, or interlocking steel mesh-like panels. This allows us to disassemble areas of the plant that are no longer in service and also makes maintenance and cleaning much easier, wasting less resources to do the same jobs.
1.3 Objective
This report’s purpose is to explain the reasoning behind every decision the Quattlebaum Engineering Co. made on behalf of Benopolis’ new drinking water treatment plant. These explanations will be supported by graphs and calculations that were used to estimate quantities such as population, sizes of facilities, concentrations of chemicals added, and distances from other industrial facilities in Benopolis.
1.4 Public Outreach
Our number one goal throughout this process is to satisfy the citizens of Benopolis, and in order to ensure that we are sufficiently doing so, we welcome all feedback. On Friday, September 28th at 1:25 p.m. there will be a town hall gathering to give citizens an opportunity to hear about our process as well as voice any opinions they may have regarding said process. We also encourage feedback via our website, https://benquatt.wixsite.com/qbaumengineerco.
2.0 Background
2.1 Regulations for Drinking Water Treatment
Drinking water treatment plants must follow strict regulations in order to uphold high standards of public health and safety. The major federal regulations that governs this process are found in the U.S. Code of Federal Regulations Title 40, or 40 C.F.R., Part 1411 and the Safe Drinking Water Act, or 42 U.S.C. § 300f et seq.2 Both of these laws give an overview of the maximum level of contaminants allowed in a drinking water sample, the methods of measuring said contaminants, and techniques for treating water to remove these contaminants.
The state of California also has its own regulations governing drinking water. These can be found in the California Code of Regulations Title 22, Division 4.3 These regulations limit specific contaminants by concentration. Water sourced from the Benopolis strait must have a dissolved oxygen concentration of 7 ppm.4 Benzene, which can be present as a result of forest fires and oil seeps, has a max contaminant limit of 1 ppb in California, which is much lower than the federal limit of 5 ppb.4 The max contaminant limit for arsenic is 2 ppm, although the objective level is 10 ppb.4
2.2 Drinking Water Treatment Plant Capacity
One of the most important aspects of sustainable infrastructure design is determining the size of a plant in order to fit the water usage needs of a community. A plant that is too large will require resources in the form of materials and energy that will go underutilized most of the time, but a plant that is too small will be unable to provide the required amount of clean water to the community. Therefore, population growth and average water usage quantities must be taken into account.
After the recent oil spill, all of the previous residents of Benopolis have decided to return to their homes. The population is low, but it is growing at a constant growth rate. In 2010, there was a population of 24,000, and with a growth rate of 1.56%, Benopolis now has a population of just over 26,000 and, assuming a steady growth rate, is expected to reach a population of 30,000 in 2039 and 32,000 in 2048 (see Appendix A).
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It has been determined that, on an average day, the normal water demand in Benopolis is 111 gpd/person. This means that, in 2018, the average water demand per day in Benopolis is approximately 2.89 million gallons per day. This, however, will vary on a day to day basis and could increase due to large events in Benopolis or decrease during population vacation times for residents. It has also been determined that the minimum water demand is 57 gpd/person, meaning that, in 2018, the minimum amount of water needed will be approximately 1.48 million gallons per day. The maximum water demand recorded in Benopolis was 165 gpd/person, which means that the maximum load on the drinking water treatment plant will be 4.30 million gallons per day. These quantities follow the national range for demand factors, as the minimum demand factor is 0.51, fitting in the national range of 0.3-0.7, and the maximum demand factor is 1.49, fitting in the national range of 1.2-3.0.
These load requirements take into account the current population, but in order to be sustainable, the plant needs to be able to support a growing population. In ten years, the average load, based on the per person usage stated above, will be approximately 3.10 million gallons per day, the minimum load will be approximately 1.59 million gallons per day, and the maximum load will be approximately 4.61 million gallons per day. This plant will take into account these loads and be prepared for population growth.
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By building for the max demand in 2043, this plant will be prepared for all factors that increase water demand within the next 25 years. It also leaves room for growth without building in excess for current years, and thus saves materials and is more sustainable overall.
2.3 Proposed Location of Drinking Water Treatment Facility
When choosing a drinking water treatment facility’s location, it is necessary to take into account several factors. Proximity to water is one of the most important factors, as the distance can affect the cost of retrieval of a water source. Proximity to industrial facilities is also important, as factories may be a source of pollutants and extra contaminants that may influence the treatment process. A plot of land in the southeastern corner of Benopolis provides a suitable location for the drinking water plant. It is land plot of about two acres that is over half a mile from the nearest industrial facility and over a mile away from the nearest residential neighborhood. Before the oil spill, it was a massive parking lot, so the land is already very level and easy to build on, and it is near the main source of water that would be used, so water retrieval from the source would be affordable and easy. While less than one and a half acres are required to meet Benopolis’ daily water demands, it is recommended that the entire two-acre plot be bought in case of any necessary expansion in the future.
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3.0 Design
There are two major sources of drinking water that are reasonable for Benopolis’ purposes: surface water and groundwater. As previously mentioned, surface water will be retrieved from the Carquinez Strait just south of Benopolis. Groundwater is also readily available via the California Coastal Basin Aquifer. This provides drinking water to many coastal California cities, including San Francisco and San Jose.
3.1.1 Surface Water Process Overview
Surface water is more readily available than groundwater. However, surface water is much more turbid, meaning it has more of a color, odor, and taste, than groundwater. This is a result of particles that are churned up from the ground underneath the surface water. The surface drinking water treatment process goes through a period of steps from its collection as dirty surface water through its distribution as clean, potable water. It first has a chemical called a coagulant added to it, which, when mixed, causes impurities within the water to clump together to form floc and settle to the bottom of a sedimentation basin. Then, the water is filtered through a sand filter to remove smaller impurities that did not form floc. Then, post chemicals are added to kill bacteria, along with UV light pulsing to sterilize them, further cleansing the water before it is distributed to homes throughout Benopolis.
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While the facility will be designed for the maximum load, there will be times that maintenance is required. Thus, backups for every step in the process have been implemented and will be used when needed in order to ensure that the water demand requirements are met all of the time.
3.1.2 Water Collection
The only problem with water collection that needed to be solved was exactly where to put the intake pipe for the collection of water. There is an industry upstream that puts out a stream of waste with a concentration of unwanted carbonaceous biochemical oxygen demand (CBOD), which depletes the amount of dissolved oxygen in the water. It has been calculated that the ultimate concentration of CBOD emitted by the industry is 151 ppm. In order to intake water at the desired CBOD level of 50 ppm, the plant’s intake pipe will be placed approximately 12.3 km downstream from the industry’s waste stream.
3.1.3 Pretreatment and Coagulants
The first step in treating drinking water is adding chemicals that will help make the treatment process more efficient. This includes adding chlorine as a disinfectant, sodium hydroxide to change the pH of the water in order to avoid pipe corrosion and rust, and a coagulant. The coagulant chosen for Benopolis’ system is a compound called alum, which produces positive charges to neutralize negative charges on colloidal, or extremely small, molecules in water. This causes the molecules to clump together, forming larger, heavier molecule groupings called floc. 📷
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Tests for alum dosages have been run for this plant, and the optimum dosage has been determined to be 7050 mgL. This, once mixed and settled, was measured to have absorbed 3561 mgLof alkalinity in the form of CaCO3. Overall, this dosage means that, as of 2018, 4.19 million kg of alum will be needed per year as a coagulant in this treatment plant. This will remove alkalinity as well as turbidity in the water.
3.1.4 Rapid Mix
Coagulation and flocculation do not begin immediately as a result of alum being added. The water and alum mixture must be mixed together for a period of 10 to 30 seconds and then allowed to settle. Rapid mixing does exactly what it says it does: it stirs the mixture together rapidly in order to ensure that the alum is colliding with particles within the water as much as possible.
The rapid mix basin for Benopolis’ water treatment plant will incorporate a detention time of 15 seconds. This, along with our maximum flow rate in 25 years, has allowed us to estimate a basin volume of 3.37 m3, or a cube with side lengths of 1.5 m. This size is relatively small due to the short detention time, making it a cheap and space efficient addition to the process.
3.1.5 Coagulation and Flocculation Chamber
Coagulation and flocculation combined are the molecular processes that form floc, or the larger clumps of unwanted sediment that can settle to the bottom of a collection basin. They settle because their increased mass is affected more by gravity than the buoyancy forces in the water, allowing the “cleaner” water to be separated and moved on to the next process.📷
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The flocculation process is not nearly as fast as the rapid mix process, and the detention time for flocculation in Benopolis’ water treatment plant is about 20 minutes. This is due to the fact that the velocity of the water within the flocculation chamber is traveling at a speed of approximately 150cmsecto 460cmsec. The paddles that are shown in Figure 6 spin at a velocity of 1rpm, which is just enough to allow the water to flow without breaking up the floc that has formed. This slow speed means that the size of the flocculation basin will be much larger than that of the rapid mix basin. The calculated volume to be used for this plant is approximately 270 m3. This incorporates the maximum water demand all the way through the year 2043.
3.1.6 Sedimentation Basin
Once floc is formed, it will not immediately sink to the bottom of the water. It requires approximately three hours of sitting almost completely still for the smaller clumps of floc to settle, and it does so in the sedimentation basin. Because the retention time is three hours, this is the largest basin in the drinking water treatment process. Its volume will be approximately 2428 m3, and it will have a cubic shape with side lengths of approximately 6.5 m3.
3.1.7 Rapid Sand Filtration
While coagulation and flocculation do a pretty good job of separating macroscopic particles from the water, it does not remove microscopic particles that are too small to be removed through sedimentation. Rapid sand filtration sends the water through layers of gravel and sand, as shown in figure 7, in order to fully remove these particles.
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Because the sand and gravel is packed so tightly, about once a day, the system experiences a period where there is increased head loss and reduced flow rate through the sand filter. This is due to clogging of the filter, and can result in increased turbidity as well. This can be solved by backwashing the system, or sending water up through the filter in order to dislodge the particles causing the “clog”. The system in Benopolis will backwash the system once a day in order to ensure maximum efficiency of the system.
3.1.8 Post Treatment
Once the water is filtered and the particles that are responsible for turbidity, or color, as well as odor and smell are removed, the final concern is for potential bacteria or viruses that may have survived the treatment process thus far. The response to this is to add chlorine to the water again as a disinfectant. The residual chlorine found previously throughout the distribution process is about 0.21 ppm, and the total amount required for disinfection was determined to be approximately 0.17 ppm, leaving the water with a total of 0.38 ppm of chlorine. This, paired with the average water demand for Benopolis in 2018, means that the average yearly chlorine requirement is about 1500 kg of chlorine. Federal law also requires fluorine to be added to public water to promote dental health. UV light pulsing is the last step in the disinfection process. UV light sterilizes any bacteria that were not killed by the chlorine disinfection process, so they will not be able to reproduce through the distribution process. This means that most bacteria and all harmful pathogens will be completely gone by the time the water hits any residential pipelines. The intensity used for the UV sterilization process will be 100 microWatts per cm3. This has been previously determined to be sufficient in sterilizing 99.9% of bacteria.
3.2.1 Groundwater Process Overview
Groundwater’s treatment process is similar to surface water’s, although there is one major difference. Groundwater has usually been in contact with minerals and thus has a hardness factor much higher than that of surface water’s. This can be fixed by adding pebble lime to the water, which softens precipitates formed by hardness. Groundwater, however, does not usually have a high turbidity, and therefore does not need to undergo coagulation and flocculation to the extent of surface water. Groundwater also experiences very little turbulence, which means that little DO can be found in groundwater.
Benopolis has access to the California Coastal Bay Aquifer for its groundwater needs, although its primary source of drinking water will be surface water from the Carquinez Strait.
3.2.2 Aeration
Aeration is the process by which dissolved oxygen is added to water and carbon dioxide is removed from water. This is done by using an injection well and forcing the groundwater from the aquifer up into the shallow, saturated soil zone. This releases the CO2 and replaces some of it with O2.5
3.2.3 Lime Addition
Hardness of water is the sum of all of the positive ions (usually minerals such as calcium and magnesium) that are found in water. The carbonated portion of this hardness can be reduced by adding pebble lime to the rapid mix tanks. In the sample collected from the California Coastal Bay Aquifer, it was calculated (Appendix I) that the required amount of lime to be added to the groundwater is approximately 3744 kg lime per day. The non-carbonated portion of the hardness can be softened by adding soda ash to the rapid mix tank. For the sample, it was calculated that 2456 kg soda ash would be needed per day to reduce the non-carbonated hardness to desired levels.
4.0 Summary
4.1 Overview
This report outlines the plans the Quattlebaum Engineering Company has made for the design of a new drinking water treatment plant in Benopolis, CA. It includes detailed step-by-step summaries and calculations of required dosages of chemicals and volumes of containment units. It also maps out the location of the facility with regard to industry, residential areas, and water source. Laws governing the methods of retrieval, monitoring level of contaminants, and methods of distribution were outlined and taken into account. This report’s goal was to show the citizens and leaders of Benopolis that everything was decided based on logic. Public health and safety, fiscal management, and sustainable design played major roles in designing this drinking water treatment facility.
4.2 Public Meeting
This plan will not reach the level of success that is desired if citizens do not accept it. That is why there will be a public town hall meeting on Friday, September 28th, 2018 at 1:25 p.m. to present the plans as well as answer any questions that have not been answered by the presentation. The citizens of Benopolis are the Quattlebaum Engineering Company’s top priority, and to ensure that all of the needs of the citizens are met, it is important that they know the facts and are on board with everything.
References
1U.S. Code of Federal Regulations. National Primary Drinking Water Regulations. Title 40 Part 141. 4-9-2004 Edition.
2United States Environmental Protection Agency. Summary of the Safe Drinking Water Act. Web. 2018.
3California Code of Regulations. Environmental Health. Title 22 Division 4. 6-12-2015 Edition.
4California State Water Resources Control. Water Quality Objectives. Web. 2018.
5Penney Engineering, Inc. Groundwater Aeration. Web. 2018.
Images
Appendix I (Calculations)
Q: An industry discharges 1 m3/s of a waste with a 5-day CBOD of 410 mg/L to your river which has a flow of 6 m3/s and a background 5-day CBOD of 1.0 mg/L. Calculate the 5-day CBOD of the river after mixing with the waste. What is the ultimate CBOD of the river after mixing with the waste? (decay rate = 0.1/day)
Cmb=(Cup*Qup)+(Cin*Qin)Qmb= (410mg/L)(1.0m3/s)+(1mg/L)(6.0m3/s)1.0m3/s+6.0m3/s= 59.43 mg/L (5-day CBODmb)
Lt=L0(1-e-kt) => L0=Lt1-e-kt= 59.43mg/L1-e(-0.1/day)(5 days)= 151.04 mg/L (CBODu)
Q: If the river is 17m wide and 5m deep, how far downstream must you place your intake of your drinking water treatment plant to keep your intake water at 5-day CBOD equal to or less than 50mg/L?
U=QA=QW*H=7m3/s17m*5m= 0.0824 m/s =>
0.0824 m/s * 86400 s/day * km/1000 m = 7.12 km/day
Lt=L0e-kt => ln(LtLo)/-k = t => ln(50mg/L59.43mg/L)/(-0.1/day)= 1.728 days
t=xU=> x=t*U => x = (1.728 days)(7.12 km/day) = 12.295 km downstream
Q: Population Predictions:
Population growth formula: y = 0.0156e0.0071x
-> found from exponential fit in Excel based on known population data
Growth Rate: 1.56%
Population in 2018: 26038 people (found by plugging 2018 for x into above equation)
Population in 2028: 27954 people (found by plugging 2028 for x into above equation)
Population in 2043: 31095 people (found by plugging 2043 for x into above equation)
Demands per person (given):
Average = 111 gpd/person
Min = 57 gpd/person
Max = 165 gpd/person
Demands (2018): (Demand per person)*(Population)
Average = (111 gpd/person)(26038 people) = 2890218 gpd
Min = (57 gpd/person)(26038 people) = 1484166 gpd
Max = (165 gpd/person)(26038 people) = 4296270 gpd
Demands (2043): (Demand per person)*(Population)
Average = (111 gpd/person)(31095 people) = 3451545 gpd
Min (57 gpd/person)(31095 people) = 1772415 gpd
Max (165 gpd/person)(31095 people) = 5130675 gpd
DFmax = QmaxQavg=4296270 gpd2890218 gpd= 1.49 (within range of national averages [1.2-3.0])
DFmin = QminQavg= 1484166 gpd2890218 gpd= 0.51 (within range of national averages [0.3-0.7])
Q: Using the optimum dosage of alum as determined in lab, what is the amount of natural alkalinity consumed (mg/L as CaCO3)? Determine the amount of alum required annually.
Optimum dosage = 0.705g100mL= 7050 mg/L
Al2(SO4)*14(H2O) + 6(HCO3-) → 2Al(OH3)(s) + 3SO42- + 14H2O + 6CO2
(7050 mgLAl2SO4)(g1000mg)(mol594g)(6 mol HCO3-1 mol alum)(1 eq HCO3-1 mol HCO3-)(100 g CaCO32 eq CaCO3) = 3.56 g/L as CaCO3
(3.56 g/L as CaCO3)(1000mgg) = 3560.6 mg/L as CaCO3 (alkalinity consumed)
Amount of alum required annually:
(0.705g100mL)(1kg1000g)(1000mLL)(3.7854Lgal)(2890218galday)(365 daysyr) = 30914513.8 kg/yr of alum
Q: Groundwater contains: CO2 = 17.6 mg/L, Ca2+ = 100 mg/L, Mg2+ = 50 mg/L, Na+ = 20 mg/L, Alk(HCO3-) = 275 mg/L as CaCO3, SO42- = 125 mg/L, Cl- = 25 mg/L
How much lime and soda ash are required to soften the water?
Soda ash = 85% sodium carbonate, lime = 90% CaO
Chemical
Concentration
Equivalents
Molecular Weight
Equivalent Weight
Concentration *as CaCO3
CO2
17.6 mg/L
2
44 g/mol
44g
40 mg/L
Ca2+
100 mg/L
2
40 g/mol
20g
250 mg/L
Mg2+
50 mg/L
2
24.4 g/mol
12.2g
205 mg/L
Na+
20 mg/L
1
23 g/mol
23g
43.48 mg/L
HCO3-
-
-
-
-
275 mg/L
SO42-
125 mg/L
2
96 g/mol
48g
130.2 mg/L
Cl-
25 mg/L
1
35.5 g/mol
35.5g
35.2 mg/L
Total Hardness = [Ca2+]* + [Mg2+]* = 250 mg/L + 205 mg/L = 455 mg/L as CaCO3
Carbonated Hardness = [HCO3-]* = 275 mg/L = 250 mg/L from Ca2+ and 25 mg/L from Mg2+
Noncarb Hardness = Total Hardness - Carb Hardness = 455 mg/L - 275 mg/L = 180 mg/L
[CaCO3] = [CO2]* + 2[Mg2+]* + [noncarb H] + [Ca2+] + [excess = 30 mg/L]
[CaCO3] = 40 mg/L + 2(25 mg/L) + 180 mg/L + 250 mg/L + 30mg/L = 550 mg/L as CaCO3
Lime required:
(550 mg/L as CaCO3)(56 mg CaO100 mg CaCO3)(kg106mg)(2890218 galday)(3.78541 Lgal)(kg lime.90 purelime)
= 3744.14 kg/day lime
Soda Ash required:
(180 mg/L as CaCO3)(106 g Na2CO3100g CaCO3)(kg106 mg)(2890218 galday)(3.78541 Lgal)(kg soda ash.85 Na2CO3)
= 2696.74 kg/day soda ash
*= as CaCO3
Q: Calculate daily Chlorine need if residual Chlorine is measured to be 0.21 mg/L.
Ct = 5 min-mg/L @ 12°C → 30 minute contact time
C12 = Ctcontact time= 5 min-mg/L30 min= 0.1667 mg/L Cl
Chlorine Need = C12 + Clresidual = 0.1667mg/L + 0.21 mg/L =0.3767 mg/L
(0.3767 mg/L Cl)(kg106 mg)(2890218 galday)(3.78541 Lgal)(365 daysyr) = 1504.29 kg/yr Cl
Tank sizing:
Rapid mix (detention time = 15 seconds):
V = Qmaxtdetention= (5130743 galday)(3.7854 Lgal)(1 m31000 L)(1 day86400 sec)(15 sec) = 3.37 m3
V = a3 => a = V1/3 = (3.37 m3)⅓ = 1.5 m (side length for cubic tank)
Coagulation/flocculation chamber (detention time = 20 minutes)
V = Qmaxtdetention = (5130743 galday)(3.7854 Lgal)(1 m31000 L)(1 day1440 min)(20 min) = 269.75 m3
Tank will not be cubic, so side lengths can vary
Sedimentation Basin (detention time = 3 hours)
V = Qmaxtdetention = (5130743 galday)(3.7854 Lgal)(1 m31000 L)(1 day24 hrs)(3 hrs) = 2427.74 m3
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