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Water Treatment Plant Design by Damora, Waite, Yu, Maroofian

Water treatment plant design group project with Alex Waite, Jenny Yu, Cyrus Maroofian, and Jonathan Damora. We chose the reliability of a turnkey solution by General Electric for our Reverse Osmosis and nanofiltration, while designing our own granular media filter. The focus of this project was to design a reliable system, which will perform at required standards no matter the influent composition.

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Water Treatment Plant Design by Damora, Waite, Yu, Maroofian

  1. 1. 1 Water Treatment Plant Design CE 484 Final Project Fall 2014 Alex Waite, Jenny Yu, Jonathan Damora, Cy Maroofian
  2. 2. 2 Table of Contents Introduction…………………………………………………………..3 The Proposal………………………………………………………...3 The Conditions/Chemicals…………………………………...3 Costs and Calculations…………………………………………..6 Construction Costs…………………………………….…6 Land Pipes Facilities Storage Permitting Operating/Maintenance…………………….……....7 Chemicals Oxidation Filtration Ultrafiltration/Reverse Osmosis Decarbonation Waste/Sludge Disposal Labor Conclusion…………………………………………..............12 References…………………………………………………………..14
  3. 3. 3 Introduction We are a private consulting company that is responsible for designing a water treatment facility. Our client is A Water Agency, who relies on the State Project Water as a source of drinking water for a city with a population for 5,000. The city is in Southern California, therefore the regulations are all based on California Regulations. Our goal is to create a functioning and affordable water treatment facility using state of the art treatment processes, including Oxidation, Granular Activated Carbon filtration, Ultrafiltration, Reverse Osmosis, Decarbonation, and Disinfection. The Proposal Due to the population of 5,000 people, we calculated the effluent flow rate for this facility to be approximately 600,000 gallons-per-day (GPD), which is equal to 416.67 gallons- per-min (GPM). This value includes a 20% contingency and an average water consumption of 100 GPD per person. Using a recovery rate of 85% for Ultrafiltration and Reverse Osmosis, as well as a 95% recovery rate for filter backwash, our influent flow rate was calculated to be 707,120.80 GPD = 491.05 GPM. Based on the groundwater analysis provided, the most efficient process to produce potable and regulation compliant water involves oxidation, dual media filtration with GAC and sand, ultrafiltration and reverse osmosis, and lastly decarbonation. After the dual media filtration, there will be sludge that is produced and must be sent out for disposal. The flow after filtration will drop down to 705,882.4 GPD, meaning that 1,238.4 GPD is backwash water. However we are not planning to perform a backwash daily, and instead plan on doing it once a month. Meaning that monthly approximately 37,151.7 gallons per month. This will cost us approximately $1,857.59 per day. After reverse osmosis there is brine that is lost. The calculated flow after the RO is 600,000 GPD, meaning that there is 105,882.4 GPD of brine, which must be sent to a wastewater treatment facility. Given the value of 5 cent per gallon of waste, we calculated that the total cost of brine removal will be $5,294.12 per day. We must also plan for the land that we need to use which is priced at $300 per square foot. Also, piping, chemicals for disinfection, and labor fees must also be considered. The Conditions - Average Turbidity = 1 NTU Target: 0.1 NTU - Very Low TOC - TDS 1000 mg/L Target: 500 mg/L - Nitrate 50 mg/L (Ion Exchange or Reverse Osmosis) Target: 10 mg/L - Soluble Manganese 0.8 mg/L (use oxidation to remove ) Target: 0.05 mg/L
  4. 4. 4 - 1,4 dioxane 10 ppb (use advanced oxidation process = UV + H2O2 or O3 + H2O2) or (use GAC) Target: < 3 ppb - pH = 6.8 (Ideal) - Alkalinity 100 mg/L as CaCO3 Target: 60-80 mg/L as CaCO3 - Brackish Water - Assume Hydrogen Sulfide Concentration is negligible Table 1: List of Contaminants with treatment options Contaminant MCLG MCL Level Present Treatment Process Source Post- treatment Change Turbidity N/A <1 NTU 1 NTU Filtration/ UF high TSS 0.1 NTU 0.9 NTU TDS N/A 500 mg/L 1000 mg/L RO Soil Leaching 500 mg/L 500 mg/L Nitrate 10 mg/L 10 mg/L 50 mg/L RO Agricultur e Runoff, Waste water <10 mg/L 40 mg/L Soluble Manganese N/A 0.05 mg/L 0.8 mg/L Oxidation/ Filtration rocks, industrial effluent, sewage & landfill leachate <0.05 mg/L 0.75 mg/L 1,4 Dioxane N/A <3 ppb 10 ppb GAC Industrial Waste <1 ppb 9 ppb pH N/A 6.5- 8.5 6.8 N/A N/A 7.1-7.3 -0.2 Alkalinity N/A Ideal 60-80 mg/L 100 mg/L Lime Softening Limestone 60 mg/L 40 mg/L Based on the contaminants given, we had to determine the most cost effective and efficient treatment processes, which can be seen in Figure 1. During oxidation, we will be using chlorine to oxidize the Manganese. However, this creates Manganese Dioxide (MnO2). Also, chlorine, when reacting with NOMs can produced DBPs such as THMs and HAA5, which are very harmful to humans. Therefore, after oxidation, we add lime softening to remove the some of the water hardness so to avoid scaling in the reverse osmosis process later on. The water now travels through a dual filter of GAC, granular activated carbon, and sand. The GAC is responsible for removing 1,4 Dioxane as well as the HAA5 by product of oxidation. The
  5. 5. 5 MnO2 is removed in the sand filter. After filtration, the water will be distributed to 2 Ultrafiltration/Reverse Osmosis self containing tanks. The reason for using 2 tanks is due to the backwash, in which we still need at least one of the tanks to be functioning. The ultrafiltration is used to remove the last of the turbidity as well as ensure that the water will not clog the reverse osmosis process. Reverse osmosis can remove not only THMs produced by oxidation, but also Total Dissolved Solids (TDS), and nitrate. Following reverse osmosis, the water enters a decarbonator, which removes CO2, thus increasing pH. We then add Sodium Bicarbonate to not only stabilize the pH but also recover some of the alkalinity. The water is now disinfected using chlorine and then sent out to be distributed. Table 2: Equipment and Sizing Process Equipment Sizing Oxidation / Disinfection 1 tank: V=130 gal In-line static mixer 3-element, 6” Diameter, with injection port Dual Media Filtration (GAC and Sand) 2 Filter Beds: V= 650ft³ each W×H×L=10’ * 5’ * 13’ UF and RO 2 Self Contained Units GE PROPAK-300-NA Tanks 10.6’ x 8’ x 14.75’ Filters 8.4’ x 6.3’ x 23’ Decarbonator LxWxH =14” x 11.7” x 57.6” Backwash Storage LxWxH = 20’ x 20’ x 25’ 80,000 gallon tank = 10,694.44 cubic ft Water Tower 40,000 Gallon Height = 100 ft Oxidation (with Chlorine) Dual Media Reve rse Osm Decarbon ator Disinfect Byprodu cts: MnO2, Slud Ultrafiltr Lime Remove s: 1,4 Dioxane Dispo Add Remo ves: CO2 Ultrafiltr Reve rse Osm Remo ves: TDS, Distribut
  6. 6. 6 Costs and Calculations Capital and Equipment Costs Table 3: Capital and Equipment Cost Estimations Capital Cost ($) Land $9,139,343.51 Pipe $572.09 Facilities $19,256.67 Treatment Processes $14,483,069.00 Storage (Water, Backwash, Chlorine) $111,266.67 Permitting $278,113.17 Total $24,031,621.11 Land Costs Considering an average per capita water consumption of 100 gpd and a 20% contingency, the estimate required flowrate of the treatment facility is 0.9284 ft3/sec. The volume needed to be delivered to the residents is 600,000 gpd. Q= 5,000 people x (100 gallons/day) x(1.2) = 600,000 gpd 600,000 gallons/day x (ft3/7.48 gallons) x (day/86400 sec) = 0.9284 ft3/sec The approximate acreage of the facility is 0.699 acres, and the cost of the land assuming it is valued at $300/sf is $9,139,343.51. Area= (0.6)^(0.7) = 0.699 acres Cost of land = 0.699 acres x (43,560 ft2/acre) x ($300/ft2) = $9,139,343.51 Pipe Costs PVC pipes are the most cost effective option with a total cost of : $ 572.09 Even though PVC pipes are less durable than steel or concrete pipes, they are lightweight, easy to assemble, and have a long lifespan which lower maintenance costs. Assuming a pipe grade of DIN 2448 and pipe length of 10 ft for each section of the water treatment system, the pipe diameter needed is 6 in. Using a Charlotte Pipe 6-in x 10-ft Sch 40 PVC DWV Pipe: $47.28 x 11 = $520.08 + 10% contingency = $572.09 Facility Costs
  7. 7. 7 Administration, laboratory, and maintenance building: CC = 235.66(Q)^0.5613 + 1220 = $19,256.67 Storage Backwash storage: Tank: 80,000 gal = 10,694.44 ft3 10,000ft3 = 20 x 20 x 25 Area= 20 x 20 = 400 ft2 = $120,000 Assume price of concrete per ft3= $4.25 Total backwash storage = $6800 Water Tower: Assuming 40,000 gallons of water for backwash, total cost is $104,266.67. Permit Apply for a permit through AQMD and CA EPA Water Board. Permitting accounts for 3% of total costs of equipment and offices. Operating and Maintenance Costs Table 4: Operating Cost Estimations Capital Cost O&M Cost Daily Cost Monthly Cost Yearly Cost Oxidation N/A $239.17 + $9,565.95 $0.56 $16.89 $9,805.12 GAC + Sand Filtration $40,350.99 + $1,259,558 $5,210.00 $14.27 $434.17 $5,210.00 Ultrafiltration + Reverse Osmosis $8,045,582 + $4,728,917.87 $565,096.79 + $442,246.40 $2798.18 $83,945.27 $1,007,343.19 Decarbonation $8660 $2,871.20 $7.73 $231.77 $2,781.20 Disinfection N/A $200.37 $0.66 $19.75 $200.37 Waste Disposal N/A $1,955,008.80 $5,356.19 $160,685.65 $1,955,008.80 Instrumentation $400,000 $2,000.00 $5.56 $166.67 $2,000.00 Labor N/A $137,280 $381.33 $11,440 $137,280 Total $14,483,069.00 $3,119,718.68 $8,862.77 $265,883.00 $3,119,718.68 Chemical Costs Table 5: Cost Estimates for Chemicals
  8. 8. 8 Chemicals Usage Prices Transportation Consumed Total Yearly Cost Chlorine (Cl2) Oxidation / Disinfection $0.12/gal 15% of total cost 125.3 gal / 2 weeks $439.54 Lime Slack Lime softening $120 / ton 15% of total cost 3.052 tons / 2 weeks $11,000.84 Sodium Bicarbonate Alkalinity recovery $200 / ton 15% of total cost 0.468 tons / 2 weeks $2,803.93 Total $14,244.31 Treatment Process Costs Influent: 707,120.8 GPD (Considering the loss of water during RO and backwash) Oxidation/Chlorination: Oxidation of Mn2+: Mn2+ standard: 0.05 mg/L Soluble Mn: 0.8 mg/L Removal amount of manganese: Mn2+ influent: 707,120.8 gal/day *3.785 L/gal *0.8*10^-6 kg/L= 2.1 kg/day Mn2+ Cl2 needed to remove Mn: 2.1 kg/day * 1 mol/54.938 g Mg2+ * 1 mol Mg2+/ 1 mol Cl2+ * 70.906 g/mol Cl2+ = 2.763 kg/day * 2.205 lb/kg = 6.1 lb/day Cl2 pure Vendor assumption: $0.12/gal of solution (15% w/v), 15% total cost added for delivery gal of solution = 2.8 kg/day * (100 L sol / 15 kg) * (1 gal/ 3.785 L) = 4.9 gal / day = 1777.6 gal / yr of solution Cost for Cl2 = 1777.6 * $0.12 = $207.97 / yr Total cost with transportation = $207.97 * 1.15 = $239.17 / yr Use 6” Flanged Static Mixer with Injection Point, 3 - Element = $1300 Sludge disposal: Sludge is produced from the GAC and UF/RO: MnO2 produced=2.141 kg Mn/day×87÷55=3.4 kg/day Dewatering power needed: 2 kw output of the motor for 24/7. Yearly power cost=2*24*365*0.02=$350/year
  9. 9. 9 Water in the sludge after dewatering: 50% in weight, wastewater send back to raw water flow Total sludge= 3.4*2=6.8 kg/day= 0.56 ton/year Disposal of sludge cost=0.56 ton/year * ($25/ton) = $14/year Decarbonator: Using Liquid-Cel Industrial Dimensions: 14” x 11.7” x 57.6” Liquid flow guidelines: 70-550 gpm (16-125 m3/hr) Estimated Cost: $8,660 + 5% Maintenance = $9093 Dual Media Filtration/Backwash: Due to the contaminants present in the influent, designing the filters ourselves seemed the most viable option. This allows us to size the tanks specifically to our flowrate, thereby reducing capital costs, as well as reducing operating costs. The approximate costs for the filtration facilities and materials include a capital cost of $1.3 million dollars and operations and management costs of $112,500. These were derived from equations given by the paper “Estimating Costs for Treatment Plant Construction” by Qasim et al. The values were estimated using our given filter area, filter media, design, and adjusting for inflation and property costs. Our proposed filtration system is 2 gravity driven dual media declining rate filters. The media chosen are sand and Granular Activated Carbon, with the smaller diameter sand on the bottom and GAC on top. Using 2 filters allows us to provide continuous filtration while one filter is undergoing backwashing or maintenance. Given that we must provide upwards of 500 gallons per minute, and assuming a filter loading rate of 5 gpm/sqft, we must have 100 square feet of filter surface area. Thus, each filter must be 50 square feet in surface area. This is achieved with tank dimensions of 10’ x 5’ x 13’. The depth is 13 feet in order to accommodate the 4 feet of media layers, the backwash troughs, and the submerged influent inlet while allowing for bed expansion during backwashing. The filters are declining rate gravity fed due to the low capital costs, low operator supervision requirement, and low maintenance due to simplicity of design. The underdrain will be a nozzle type due to the increased media fluidization when backwashing and the fact that no drainage material is required. The backwash troughs will be located 12 feet from the bottom of the bed, with two troughs per filter. There will also be surface wash nozzles in place along the troughs in order to increase fluidization of the media and break the mud balls. The media layers are sized with a depth of 30 cm for the GAC layer on top and a depth of 90 cm for the sand layer. This ratio was taken from a study showing the highest removal of TOC using beds the same depth.. The diameter of the particles is given by relating the L/D ratio to the ratios of particle diameters given by the equations below.
  10. 10. 10 From the first equation we get that the diameter of the sand particles are equal to .772 times the diameter of the granular activated carbon particles. The density of GAC was found to be 130 lb/cft while the density of sand was taken to be 162 lb/cft. The L/D ratio was taken to be 1000. Inputting these values into the above equations result in a diameter of 0.045 inches or less for the sand particles, and a diameter of 0.06 inches or less for the GAC particles. The volume of media required for each filter is approximately 50 cubic feet of GAC and 150 cubic feet of sand. The backwash water will come from a water tower located next to the filtration basin. The tower will be 100 feet tall with a storage volume of 40,000 gallons and providing 43 psi of pressure at the filter underdrain.. This will be sufficient for one backwash cycle,which will last approximately 20 minutes at an average flow rate of 2000 GPM . It will be filled by influent water pumped into the tower. The backwash will be sent to a basin designed to hold 80,000 gallons, two backwash cycles, until it can be discharged to a treatment facility. Each filter will undergo backwashing once a month, never on the same day, in order to provide continuous flow. Immediately following the backwash cycle the filters will run filter to waste until turbidity stabilizes, in order to maintain stability in effluent. Ultrafiltration/Reverse Osmosis: Capital Costs: -0.0007Q^2 + 1203.1Q +2000000 = $4,728,917.87 O&M Costs = 391189Q+207533 = $442,246.40 The water leaves the filtration basin and it enters a 1650 gallon multipurpose storage tank connected to one of the 2 vendor supplied PROPAK-300-NA combination uF/RO filtration systems. The benefits of purchasing a packaged system are numerous. The largest benefits include the high efficiency of the PROPAK design (including the optional Integral Concentrate Recovery system that increases recovery to 85%) vendor equipment support, ease of installation, increased distribution of the treatment process (allowing for treatment to continue even if one is down for repair), and the ease of a single source for replacement parts and consumables. We have included the vendor supplied fact sheet that lists the components included in the system as well as technical specifications used to connect them to our plant. We have 2 individual platforms, with each including a compact multifunctional tank: break, 27 modules for ultrafiltration with a 0.02 micron nominal pore diameter, 500 micron automated pre-screening, instruments to measure flow, conductivity, pH, Pressure, Chlorine, Temperature, and Turbidity. This will provide our reverse osmosis with sufficient protection from harmful influent variations as well as provide the Quality Assurance for our final effluent quality.
  11. 11. 11 Ultrafiltration: Capital Cost = 0.0003 x^3 – 0.8109 x^2 + 2016.9 x + 38246 = $8,045,582 Operations and Maintenance Cost = 241.28 x + 17092 = $565,096.79 Disinfection/Chlorination: Assume: y= 0.35x - 0.85 Need residual of 0.5 mg/L 0.5=0.35x-0.85 → x = 3.857 mg/L Cl- 3.857mg/L*1 kg/10^6mg*3.78541L/gal*600,000 gal/day*365 day/yr = 5.12 lb/day Cl2 Use same vendor as oxidation: 2.31 kg * (100 L / 15 kg) * (1 gal / 3.785 L) = 4.1 gal/day solution = 1489.2 gal / yr solution Cost = 1489.2 gal/yr * ($0.12 / gal) = $174.24 / yr Cost with transportation = $200.37 / yr Total chlorine (from oxidation and disinfection): Total chlorine needed in chlorination from oxidation and disinfection steps: T=3266.8 gal / yr Total Cost=$439.54/year Static Inline Mixer: 1 @ $1300 = $1300 Chlorine Container: Use Chem-Tainer 130 Gallon Vertical Bulk Storage Tank (23” D x 76” H) = $200.00 Waste-stream Disposal: Waste stream is mainly from backwash from dual-media filters and RO’s reject water. Total amount is 37151.7 gallons per month for backwash and 105882.4 GPD for RO. All water is sent through the pipes. Disposal costs for backwash: $0.05/gal*37151.7 gal/month * 12 months = $22,291 /year Disposal costs for brine: $0.05/gal * 105882.4 gal/day = $5294.12 / day = $1,932,353.80 / year Total waste-stream disposal = $1,954,644.80 / year Labor Costs: If we assume a total of 3 workers for a 24/7 operation, this would be impossible to achieve legally. If we assume that there are 2080 workable hours in a year and that these workers are paid hourly at $22/hour, the total cost would be $22/hour x 2080 hours/year x 3 workers = $137,280. If we account for the lack of workers and have a minimum of 5 workers working 8 hour shifts at $22 per hour, total cost would be 22 x 8 x 7 x 52 x 5 = $320,320. Electronic Monitoring System (SCADA): Implementing an electronic monitoring system (SCADA) costs ≈$400,000 Assume yearly O&M of $2,000/yr for maintenance and repairs.
  12. 12. 12 Cost of Water Produced Capital Cost = $24,031,621.11 O&M Cost =$3,119,718.68 NPV = $24,031,621.11 + $3,119,718.68 (P/A, 0.07, 30) = $24,031,621.11 + $3,119,718.68*((1.07)^30 - 1)/(0.07*(1.07)^30)) = $62,744,338.69 Cost of Water Produced = $62,744,338.69/ (600,000 gal/day x 365 days/year x 30 years) = $0.00955/gal = $9.55/1000 gal Conclusion Through our data and calculations, it is apparent this project is a competitive design for a water treatment facility. We tried to utilize the most effective treatment processes without spending large amounts of money on chemical dosing and storage. For example, we decided against UV radiation because of the high capital and operating cost, and since nitrate will have to be removed prior to UV treatment or nitrate will be reduced into the much more toxic form of nitrite. The only viable options for nitrite removal in drinking water are reverse osmosis and ion exchange. Taking into account the other contaminants present in the groundwater, such as 1,4- dioxane, we decided against any advanced oxidation process in favor of having GAC filtration for dioxane removal and reverse osmosis for nitrate. We determined that this would provide the highest quality water for the cheapest price. We were fortunate to find a General Electric manufactured RO Unit bundled with ultrafiltration, not only saving you money compared to designing and manufacturing a system ourselves, but also made the process more efficient due to the proprietary technology contained within. The largest obstacles that we ran into were the pricing for the equipment, both operating and construction. Our numerous attempts to contact General Electric produced no information, thus we had to estimate the cost based on other Reverse Osmosis Facilities. Many of the formulas that we used were from 20-30 years ago, therefore the values given for pricing are rough estimations. To make up for this we made sure that we rigorously investigated and accounted for the assumptions and default values used in creating the equations, such as adjusting for our own property cost. We also included inflation rates to adjust the pricing accordingly. We calculated the plants revenue to be $8.6 million/yr with a profit of $5.48 million/yr. To recover all the capital costs, we would need 3 years of operation. So that makes our Internal Rate of Return (IRR) ≈ 3. Meaning, that for 30 years of operation, that total estimated profits would be: (30-3)*5.48=$148 million.
  13. 13. 13 References physical-chemical-way.htm Sharma, Jwala Raj. (2010, May). Development of a Preliminary Cost Estimation Method for Water Treatment Plants. University of Texas at Arlington. h/CB1258EN.pdf Lecture Notes and Slides CE - 484 Dr. Arturo Burbano