DAF Unit Design and Detailed Specifications
Budget: $250 – $750 USD
Review, update and complete design of current DAF tank design. See attached drawing and specifications. DAF footprint must remail the same. Focus is on internal piping, etc. Provide BOM for all required items. BOM does not need to be product procific, only spec'ed. Awarded designer will be given the CAD files.
Product will be additional CAD files, modified CAD files
### Equipment and System Design for 12,000 GPD
- **DAF Unit**: A compact, high-rate DAF (e.g., AquaDAF or Clari-DAF) with an SLR of 12–20 gpm/ft², requiring a tank size of ~1 m². Circular units are more efficient (3-minute retention time) than rectangular ones (20–30 minutes).
- **Recirculation System**: A centrifugal pump (80–120 psi, ~1–2 HP) and air compressor (1–2 HP) to handle 8–12% recycle flow (~1,000–1,500 GPD).
- **Chemical Dosing**: Dosing pumps for coagulants (10–50 gpm), flocculants (0.1–1 gpm), and pH adjusters.
- **Filtration**: Dual-media filters (sand/anthracite) with a filtration rate of 5–10 m/h, sized for 12,000 GPD.
- **Disinfection**: Chlorine dosing system or UV reactor sized for 8.33 gpm.
- **Monitoring**: Inline turbidimeters, pH meters, and chlorine analyzers.
- For a 12,000 GPD system, a high-rate DAF (e.g., AquaDAF or Enflo-DAF) with a surface loading rate (SLR) of 12–20 gpm/ft² is suitable, requiring a tank surface area of approximately 0.5–1 m².
- **Equipment**: DAF tank (circular or rectangular), recirculation pump, air compressor, saturation tank, skimming system, and lamella plates (optional for enhanced separation).
- **Standards Compliance**: Removes up to 90–99% of TSS, algae, and color, achieving effluent turbidity <1 NTU, which meets WHO/EPA guidelines for drinking water clarity.
- **Procedure**:
- Add coagulants (e.g., aluminum sulfate [alum], ferric chloride, or poly-aluminum chloride) to destabilize suspended particles. Dosage typically ranges from 10–50 mg/L, depending on water quality (determined by jar tests).
- Adjust pH (e.g., using sodium hydroxide or sulfuric acid) to optimize coagulation, typically to a pH of 6–8.
- Add flocculants (e.g., polyelectrolytes or polymers) to enhance floc formation. Dosage is usually 0.1–1 mg/L.
- Mix the water in a coagulation tank (rapid mixing, 100–200 rpm, 1–2 minutes) followed by a flocculation tank (slow mixing, 20–50 rpm, 10–20 minutes) to form larger, low-density flocs suitable for flotation.
- **Equipment**: Chemical dosing pumps, rapid mixers, flocculation tanks with variable frequency drive (VFD) mixers.
- **Standards Compliance**: Reduces turbidity, color, and organic matter, which are critical for meeting WHO/EPA standards for turbidity (<1 NTU) and total organic carbon (TOC).
### Procedures for Producing WHO/EPA-Standard Drinking Water Using DAF
#### 1. **Raw Water Intake and Screening**
- **Purpose**: Remove large debris and coarse particles to protect downstream equipment.
- **Procedure**:
- Source raw water from a surface water body (e.g., lake, river, or reservoir) or groundwater.
- Pass the water through coarse screens or hydrocyclones to remove large debris like leaves, twigs, or sand. This step reduces the load on the DAF system.
- For a 12,000 GPD system (approximately 8.33 gallons per minute or 31.5 m³/h), a simple bar screen or fine mesh (1–5 mm) is sufficient.
- **Equipment**: Bar screens, shaker screens, or hydrocyclones.
- **Standards Compliance**: Ensures initial reduction of total suspended solids (TSS), aligning with WHO/EPA requirements for pre-treatment.
#### 2. **Coagulation and Flocculation**
- **Purpose**: Destabilize and aggregate fine particles and colloids to form larger flocs that can be floated by air bubbles in the DAF unit.
#### 3. **Dissolved Air Flotation (DAF) Process**
- **Purpose**: Remove flocculated particles, algae, oils, and other low-density contaminants by floating them to the surface with microbubbles.
- **Procedure**:
- Pump a portion of clarified effluent (8–12% of total flow, or ~1,000–1,500 GPD for a 12,000 GPD system) into a saturation tank, where air is dissolved under high pressure (400–600 kPa or 60–90 psi).
- Release the pressurized, air-saturated water through nozzles or valves into the DAF contact zone, forming microbubbles (30–50 microns) that attach to flocs.
- In the flotation tank, bubbles lift flocs to the surface, forming a sludge layer (skimmings) that is removed by a skimming device.
- Collect clarified water from the bottom of the tank via an effluent discharge baffle.
#### 4. **Post-DAF Filtration**
- **Purpose**: Further reduce residual suspended solids, turbidity, and fine particles to meet stringent WHO/EPA standards.
- **Procedure**:
- Pass DAF effluent through granular media filters (e.g., sand, anthracite, or dual-media filters) to remove remaining particles. Typical filtration rates are 5–10 m/h.
- Backwash filters periodically (every 24–48 hours) to maintain efficiency.
- For enhanced removal of dissolved organic matter, consider activated carbon filtration as an additional step.
- **Equipment**: Granular media filters, backwash pumps, and activated carbon filters (if needed).
- **Standards Compliance**: Ensures turbidity <0.3 NTU (EPA) and removes residual organic matter, aligning with WHO/EPA requirements.
#### 5. **Disinfection**
- **Purpose**: Eliminate pathogens (bacteria, viruses, protozoa) to meet WHO/EPA microbiological standards.
- **Procedure**:
- Apply disinfectants such as chlorine (1–2 mg/L residual), chloramine, or UV disinfection to achieve a 4-log reduction of pathogens.
- Ensure a contact time (CT) value sufficient to meet EPA’s Surface Water Treatment Rule (e.g., CT of 10–100 mg·min/L for chlorine, depending on pH and temperature).
- Monitor residual disinfectant levels to ensure compliance with WHO/EPA limits (e.g., chlorine residual <4 mg/L).
- **Equipment**: Chlorine dosing system, UV reactors, or ozone generators.
- **Standards Compliance**: Achieves <1 CFU/100 mL for total coliforms and no detectable E. coli, per WHO/EPA standards.
#### 6. **pH Adjustment and Stabilization**
- **Purpose**: Adjust pH and stabilize water to prevent corrosion or scaling in distribution systems.
- **Procedure**:
- Adjust pH to 7–8.5 using sodium hydroxide or calcium carbonate.
- Add corrosion inhibitors (e.g., orthophosphates) to meet EPA’s Lead and Copper Rule.
- **Equipment**: Chemical dosing pumps, pH meters.
- **Standards Compliance**: Ensures pH and alkalinity meet WHO/EPA guidelines (pH 6.5–8.5, alkalinity >20 mg/L as CaCO₃).
#### 7. **Monitoring and Quality Control**
- **Purpose**: Verify that the treated water meets WHO/EPA drinking water standards.
- **Procedure**:
- Regularly monitor key parameters: turbidity (<0.3 NTU), total coliforms (<1 CFU/100 mL), pH (6.5–8.5), residual chlorine (<4 mg/L), and specific contaminants (e.g., arsenic, lead, or nitrates) as per WHO/EPA guidelines.
- Conduct jar tests to optimize coagulant and flocculant dosing.
- Perform daily checks on flow rates, pressure readings, and air injection efficiency in the DAF system.
- **Equipment**: Turbidimeters, pH meters, chlorine analyzers, and microbial testing kits.
- **Standards Compliance**: Ensures all parameters meet WHO’s Guidelines for Drinking-water Quality and EPA’s National Primary Drinking Water Regulations.
#### 8. **Sludge Management**
- **Purpose**: Properly handle and dispose of sludge generated from DAF and filtration processes.
- **Procedure**:
- Collect flotation sludge (5% dry solids content) and settled solids from the DAF tank.
- Dewater sludge using a filter press or centrifuge to reduce volume and disposal costs.
- Dispose of dewatered sludge in accordance with local regulations (e.g., landfill or incineration).
- **Equipment**: Sludge pumps, filter press, or centrifuge.
- **Standards Compliance**: Ensures compliance with EPA regulations for sludge disposal (40 CFR Part 503).
Product will be additional CAD files, modified CAD files
### Equipment and System Design for 12,000 GPD
- **DAF Unit**: A compact, high-rate DAF (e.g., AquaDAF or Clari-DAF) with an SLR of 12–20 gpm/ft², requiring a tank size of ~1 m². Circular units are more efficient (3-minute retention time) than rectangular ones (20–30 minutes).
- **Recirculation System**: A centrifugal pump (80–120 psi, ~1–2 HP) and air compressor (1–2 HP) to handle 8–12% recycle flow (~1,000–1,500 GPD).
- **Chemical Dosing**: Dosing pumps for coagulants (10–50 gpm), flocculants (0.1–1 gpm), and pH adjusters.
- **Filtration**: Dual-media filters (sand/anthracite) with a filtration rate of 5–10 m/h, sized for 12,000 GPD.
- **Disinfection**: Chlorine dosing system or UV reactor sized for 8.33 gpm.
- **Monitoring**: Inline turbidimeters, pH meters, and chlorine analyzers.
- For a 12,000 GPD system, a high-rate DAF (e.g., AquaDAF or Enflo-DAF) with a surface loading rate (SLR) of 12–20 gpm/ft² is suitable, requiring a tank surface area of approximately 0.5–1 m².
- **Equipment**: DAF tank (circular or rectangular), recirculation pump, air compressor, saturation tank, skimming system, and lamella plates (optional for enhanced separation).
- **Standards Compliance**: Removes up to 90–99% of TSS, algae, and color, achieving effluent turbidity <1 NTU, which meets WHO/EPA guidelines for drinking water clarity.
- **Procedure**:
- Add coagulants (e.g., aluminum sulfate [alum], ferric chloride, or poly-aluminum chloride) to destabilize suspended particles. Dosage typically ranges from 10–50 mg/L, depending on water quality (determined by jar tests).
- Adjust pH (e.g., using sodium hydroxide or sulfuric acid) to optimize coagulation, typically to a pH of 6–8.
- Add flocculants (e.g., polyelectrolytes or polymers) to enhance floc formation. Dosage is usually 0.1–1 mg/L.
- Mix the water in a coagulation tank (rapid mixing, 100–200 rpm, 1–2 minutes) followed by a flocculation tank (slow mixing, 20–50 rpm, 10–20 minutes) to form larger, low-density flocs suitable for flotation.
- **Equipment**: Chemical dosing pumps, rapid mixers, flocculation tanks with variable frequency drive (VFD) mixers.
- **Standards Compliance**: Reduces turbidity, color, and organic matter, which are critical for meeting WHO/EPA standards for turbidity (<1 NTU) and total organic carbon (TOC).
### Procedures for Producing WHO/EPA-Standard Drinking Water Using DAF
#### 1. **Raw Water Intake and Screening**
- **Purpose**: Remove large debris and coarse particles to protect downstream equipment.
- **Procedure**:
- Source raw water from a surface water body (e.g., lake, river, or reservoir) or groundwater.
- Pass the water through coarse screens or hydrocyclones to remove large debris like leaves, twigs, or sand. This step reduces the load on the DAF system.
- For a 12,000 GPD system (approximately 8.33 gallons per minute or 31.5 m³/h), a simple bar screen or fine mesh (1–5 mm) is sufficient.
- **Equipment**: Bar screens, shaker screens, or hydrocyclones.
- **Standards Compliance**: Ensures initial reduction of total suspended solids (TSS), aligning with WHO/EPA requirements for pre-treatment.
#### 2. **Coagulation and Flocculation**
- **Purpose**: Destabilize and aggregate fine particles and colloids to form larger flocs that can be floated by air bubbles in the DAF unit.
#### 3. **Dissolved Air Flotation (DAF) Process**
- **Purpose**: Remove flocculated particles, algae, oils, and other low-density contaminants by floating them to the surface with microbubbles.
- **Procedure**:
- Pump a portion of clarified effluent (8–12% of total flow, or ~1,000–1,500 GPD for a 12,000 GPD system) into a saturation tank, where air is dissolved under high pressure (400–600 kPa or 60–90 psi).
- Release the pressurized, air-saturated water through nozzles or valves into the DAF contact zone, forming microbubbles (30–50 microns) that attach to flocs.
- In the flotation tank, bubbles lift flocs to the surface, forming a sludge layer (skimmings) that is removed by a skimming device.
- Collect clarified water from the bottom of the tank via an effluent discharge baffle.
#### 4. **Post-DAF Filtration**
- **Purpose**: Further reduce residual suspended solids, turbidity, and fine particles to meet stringent WHO/EPA standards.
- **Procedure**:
- Pass DAF effluent through granular media filters (e.g., sand, anthracite, or dual-media filters) to remove remaining particles. Typical filtration rates are 5–10 m/h.
- Backwash filters periodically (every 24–48 hours) to maintain efficiency.
- For enhanced removal of dissolved organic matter, consider activated carbon filtration as an additional step.
- **Equipment**: Granular media filters, backwash pumps, and activated carbon filters (if needed).
- **Standards Compliance**: Ensures turbidity <0.3 NTU (EPA) and removes residual organic matter, aligning with WHO/EPA requirements.
#### 5. **Disinfection**
- **Purpose**: Eliminate pathogens (bacteria, viruses, protozoa) to meet WHO/EPA microbiological standards.
- **Procedure**:
- Apply disinfectants such as chlorine (1–2 mg/L residual), chloramine, or UV disinfection to achieve a 4-log reduction of pathogens.
- Ensure a contact time (CT) value sufficient to meet EPA’s Surface Water Treatment Rule (e.g., CT of 10–100 mg·min/L for chlorine, depending on pH and temperature).
- Monitor residual disinfectant levels to ensure compliance with WHO/EPA limits (e.g., chlorine residual <4 mg/L).
- **Equipment**: Chlorine dosing system, UV reactors, or ozone generators.
- **Standards Compliance**: Achieves <1 CFU/100 mL for total coliforms and no detectable E. coli, per WHO/EPA standards.
#### 6. **pH Adjustment and Stabilization**
- **Purpose**: Adjust pH and stabilize water to prevent corrosion or scaling in distribution systems.
- **Procedure**:
- Adjust pH to 7–8.5 using sodium hydroxide or calcium carbonate.
- Add corrosion inhibitors (e.g., orthophosphates) to meet EPA’s Lead and Copper Rule.
- **Equipment**: Chemical dosing pumps, pH meters.
- **Standards Compliance**: Ensures pH and alkalinity meet WHO/EPA guidelines (pH 6.5–8.5, alkalinity >20 mg/L as CaCO₃).
#### 7. **Monitoring and Quality Control**
- **Purpose**: Verify that the treated water meets WHO/EPA drinking water standards.
- **Procedure**:
- Regularly monitor key parameters: turbidity (<0.3 NTU), total coliforms (<1 CFU/100 mL), pH (6.5–8.5), residual chlorine (<4 mg/L), and specific contaminants (e.g., arsenic, lead, or nitrates) as per WHO/EPA guidelines.
- Conduct jar tests to optimize coagulant and flocculant dosing.
- Perform daily checks on flow rates, pressure readings, and air injection efficiency in the DAF system.
- **Equipment**: Turbidimeters, pH meters, chlorine analyzers, and microbial testing kits.
- **Standards Compliance**: Ensures all parameters meet WHO’s Guidelines for Drinking-water Quality and EPA’s National Primary Drinking Water Regulations.
#### 8. **Sludge Management**
- **Purpose**: Properly handle and dispose of sludge generated from DAF and filtration processes.
- **Procedure**:
- Collect flotation sludge (5% dry solids content) and settled solids from the DAF tank.
- Dewater sludge using a filter press or centrifuge to reduce volume and disposal costs.
- Dispose of dewatered sludge in accordance with local regulations (e.g., landfill or incineration).
- **Equipment**: Sludge pumps, filter press, or centrifuge.
- **Standards Compliance**: Ensures compliance with EPA regulations for sludge disposal (40 CFR Part 503).