Wastewater Lagoons: Past Present & Future Presented by: Tom Hinde of Air Diffusion Systems

Size: px

Start display at page:

Download "Wastewater Lagoons: Past Present & Future Presented by: Tom Hinde of Air Diffusion Systems"

Cecily Young
6 years ago
Views:

1 MWEA Lagoon Seminar Battle Creek, MI Tuesday, May 10 th 2016 Wastewater Lagoons: Past Present & Future Presented by: Tom Hinde of Air Diffusion Systems

2 Tom Hinde Bio 3 rd Generation Water & Wastewater consultant at Air Diffusion Systems Established in 1965 (formerly Hinde Engineering Co.) Manufacturer of fine bubble aeration for both water and wastewater treatment 1,000 domestic / industrial wastewater systems 4,000 reservoir, lake, aquaculture, marina, & ice melting systems

3 Presentation Objectives 1. Wastewater & Treatment History 2. Compare Activated Sludge & Lagoon Processes 3. Aerated-Facultative Lagoon System 4. Oxygenation, Mixing, & Types of Aeration 5. Nutrient Removal 6. Advanced (Modern) Aerated Lagoon

4 Wastewater Definition: Wastewater, also written as waste water, is any water that has been adversely affected in quality by anthropogenic influence. Wastewater can originate from a combination of domestic, industrial, commercial / agricultural activities, surface runoff or storm water, and from sewer inflow or infiltration. * Source = Wikipedia

5 Wastewater Treatment Definition: Wastewater treatment is a process to convert wastewater - which is water no longer needed or suitable for its most recent use - into an effluent that can be either returned to the water cycle with minimal environmental issues or reused * Source = Wikipedia

6 History of Wastewater Treatment The first human communities were scattered over wide areas and disposed of waste via holes in the ground Around 3500 BC, the first home drainage systems were used in parts of the Mesopotamian empire to carry excreta away from homes and divert them to streams & rivers The Indus, Egyptian, Greek, & Roman civilizations all incorporated various forms of sanitation into their cities and buildings With the fall of the Roam Empire, a sanitary dark ages persisted for over 1300 years ( AD) It wasn t until the late 1800 s and early 1900 s where many countries began to experiment and adopt advancements in wastewater collection and treatment practices

7 History of Wastewater Treatment

8 History of Wastewater Treatment

9 For Thousands Of Years, Wastes Have Been Disposed Into Convenient Water Ways, Mainly Rivers

10 The Original Wastewater Treatment System: The Rolling River

11 Waste Is Dumped Into A River, It s Treated Biologically For Miles Downstream

12 Wastes Are Naturally Treated By The Food Chain

13 Natures Scavengers

15 It s amazing how many places can support life even in hostile environments like WASTEWATER.

16 Keys To Wastewater Treatment 1) Quantify 2) Analyze 3) Implement Maintain ecological balance Pretreatment is critical (no inorganics) Understand oxygenation & mixing goals Design for the future using efficient technologies Complete system approach Evaluate & incorporate nutrient removal & recirculation Measure sludge every 3 5 years & have a mitigation plan in place

17 Wastewater Treatment Factors Temperature ph / Alkalinity Dissolved Oxygen Retention Time CNP Ratios & Trace Elements

18 Wastewater Temperature Treatment is temperature dependent. (Q-10) The colder the water temperature, the longer it takes for biologically process to work The optimal water temperature range is between 60-95

19 Cell Volume is Based on Winter Reaction Rates to meet NPDES limits

20 ph / Alkalinity Most aerobic organisms prefer a ph between 6 & 9 ph is affected by pollutants & impurities 7.14 parts of alkalinity are required for each part of ammonia to be removed

21 Dissolved Oxygen Wastewater is mainly comprised of BOD, TSS, & NH3 Each of these items has an associated oxygen demand: 1.4 pounds of oxygen / pound of BOD 0.7 pounds of oxygen / pound of TSS 4.7 pounds of oxygen / pound of NH3 Satisfying total oxygen demand is critical for treatment success

22 How to determine CFM for Oxygen Demands

23 Oxygenation is Based on Summer Reaction Rates to Maintain 2 mg/l of D.O. on the Bottom

24 Retention Time The longer the retention time, the better the effluent

25 CNP Ratios & Trace Elements Maintaining proper ratios of carbon, nitrogen, & phosphorus is critical to all major wastewater processes: 100 ppm Carbon 5 ppm Nitrogen 1 ppm Phosphorus Trace elements are also very important!

26 Wastewater Microbiology A Variety of Microorganisms Exist in Wastewater: Anaerobic Bacteria Facultative Bacteria Aerobic Bacteria Fungi Protozoa (Amoeboids, Flagellates, Ciliates) Rotifers Nematodes, Roundworms, & Metazoa

27 Two Main Forms of Wastewater Treatment 1) Activated Sludge Processes Mechanical & chemical separation of wastes H 2 0 2) Lagoon Processes Natural & biological separation of wastes from H 2 0

29 1) Activated Sludge Processes Mechanical / Chemical Process Low Land Requirements Short Retention Times ( ~ 2 Days) # BOD / 1000 cubic feet Sludge Digestion = External Energy Intensive ~ $15 Per Gallon Treated

30 Traditional Activated Sludge & Advanced Treatment Works Very Well But It s Costly, Requires Chemicals & Accumulates Sludge

32 2) Lagoon Processes Natural / Biological Process Large Land Requirements Long Retention Times (20+ Days) 0.5 # BOD / 1000 cubic feet Sludge Digestion = Internal Low Energy Requirements ~ $3 Per Gallon Treated

33 Lagoon History & Facts The first lagoons (stabilization ponds) were developed and used by the Sumerians and Romans more than 5,500 years ago. The first recorded use of a lagoon in America was in San Antonio (1901) There are more than 8,000 wastewater lagoons currently in use in America today Advanced aerated lagoons can meet single digit BOD, TSS, & NH3 removal year round, even in cold climates

34 Lagoons Come In Many Shapes & Sizes

35 4 Types of Lagoons Anaerobic Photosynthetic Aerated (Aerobic) Aerated (Facultative)

36 Anaerobic Lagoons Process Advantages Disadvantages Anaerobic Soluble BOD Conversion 50 60% BOD Removal Partial Treatment Solids Digestion Low Operating Costs Uncontrolled Odors

Surface Area Load Limited Seasonally High Degrees of Treatment Low

37 Photosynthetic Lagoons Process Advantages Disadvantages Aerobic Soluble BOD Conversion Facultative & Anaerobic Solids Digestion Surface Area Load Limited Seasonally High Degrees of Treatment Low Operating Costs Largest Land Requirements Seasonally Poor Performance Odors

Process Complete Mix System No Settling Of Solids No

38 Aerated Aerobic Lagoons Process Advantages Disadvantages Aerobic Soluble BOD Conversion Modified Mixed Liquor Process Complete Mix System No Settling Of Solids No Odors Complex Operation Sludge High Energy Requirements Expensive

39 Aerated Facultative Lagoons Process Advantages Aerobic Soluble BOD Conversion Aerobic, Facultative, & Anaerobic Sludge Digestion Non Mixed Liquor Process Partial Mix System Year Round Treatment Internal Sludge Digestion Flow & Load Equalization Low Energy Low Maintenance

40 Aerated-Facultative Lagoon Detail

41 How Does An Aerated Facultative Lagoon Work? All 3 process occur in a properly oxygenated lagoon. Anaerobic Facultative Aerobic When properly designed, provides efficient oxygenation and mixing Handles shock flows and loads well

43 Working Closely With Bacteria & Biology Duplicates water treatment similarly to a Rolling River Provides air at the sludge / water interface Creates aerobic conditions throughout the entire water column (2 ppm + no odors) Digests sludge and organics internally No sludge Hauling 20 + years

44 What Bottom Oxygenation Does IN THE PRESENCE OF OXYGEN: Organic waste from man s activities becomes food Bacteria, aquatic insects, snails, worms, and fish convert unwanted waste The living cycle is created through bottom oxygenation which is the vital link for sludge digestion and water treatment

46 Before Oxygenation

47 After Oxygenation

48 Oxygen Transfer 02 transfer takes place at the contact surface between air and water For a given volume of air, fine bubbles create a significantly greater contact surface than coarse bubbles and surface / jet aeration The diameter of coarse bubbles > 1/4th inch The diameter of fine bubbles < 1/8th inch

49 Bubble Size Matters Diameter inches # of Bubbles Volume cu mm Surface Area sq mm Factor Increase 1 1 8,584 2, /2 8 8,584 4, / ,584 16, /100 1,000,000 8, ,

50 3 Subcategories of Aeration Systems Submerged Fine Bubble Coarse Bubble Static Tubes Jet Surface Low Speed Turbine High Speed Floating Aspirating Rotor Brush / Rotating Disk Cascade Step Aeration

51 Surface & Jet Aeration Ideally suited for very shallow applications Horsepower intensive Difficult to force a bubble down! Very turbulent process

52 Coarse Bubble Aeration Larger bubbles rise quickly (1-2 / sec) This fast rise rate and large bubble diameter creates a turbulent bubble Turbulent bubbles provide poor oxygenation & mixing and are also energy inefficient

53 Fine Bubble Aeration Smaller bubbles rise slowly (0.8 / second ) This slow rate of rise creates a non-turbulent (laminar) flow of both air & the surrounding water The slower rise rate allows for prolonged contact time with the water, allowing for greater O2 transfer efficiency Fine bubbles have very little bubble slippage, so that nearly all the water surrounding each bubble moves with it

55 Fine Bubble Aeration The vertical movement of bubbles mixes and moves oxygen throughout all levels of the water column This movement pumps dense oxygen deficient water to the surface. For every gallon of water displaced one must replace it The end result is highly efficient oxygenation with unsurpassed mixing rates

56 Mixing: Laminar vs. Turbulent Flow Both bubble diameter and rise rate effect how a bubble moves through water and it s ability to efficiently LIFT water to the surface This movement provides the necessary mixing in order to disperse oxygen between any two diffusers Laminar bubbles provide more efficient mixing and circulation than turbulent bubbles This difference can be calculated mathematically using a fundamental principle of fluid dynamics known as Reynolds Number (Re #) Bubble diameter is characterized as laminar for Re < 2,100 and fully turbulent for Re > 10,000

57 Mixing: Laminar vs. Turbulent Flow

58 How to Determine CFM for Mixing

59 The Largest Co$t of an Aerated Lagoon Aerator Motor Horsepower SCFM required for mixing is often larger than the requirements for oxygenation At 10 cents a KWH each HP cost about $2 per day Dr Clemson University states the HP for surface aerators is as follows: 30 HP per Million Gallons = Primary Lagoon 5 HP per Million Gallons = Secondary Lagoon Fine Bubble 10 ft WD 5 HP per MG = Primary Lagoon 2 HP per MG = Secondary Lagoon EX) 2 Cell Lagoon with 2 x 1 MG cells (2 MG total volume) Surface air = 35 HP Fine bubble= 7 HP Overall power savings = 28 HP or $56 per day (5 times) $20,440 per year saved

61 Lagoon Nutrient Removal Nitrogen & Phosphorus limits are quickly being implemented across America Meeting low single digit limits is very costly Estimated removal rates via biological uptake: Nitrogen = 25% 95% Phosphorus = Up to 50%

62 Ammonia & Nitrogen in Wastewater Type of Nitrogen Strong Medium Weak Organic-N, mg/l Ammonium-N, mg/l Total-N, mg/l

63 Problems With Nitrogen: Compounds containing nitrogen discharged from wastewater treatment plants can have harmful side effects: Toxicity to fish and aquatic life - Contributes to algal growth - Depletes DO Reduction of chlorine disinfection efficiency Adverse public health effects Reduction in the suitability of water for reuse

64 How Much Nitrogen Is Too Much? This depends on several factors - ph - Temperature - Dilution Factor 10 mg/l of TKN is considered dangerous for infants and the elderly

65 Nitrogen Removal Over The Last 50 Years Understanding has been vastly improved South Tahoe Water District Testing Equipment Easy to monitor WWTP

66 Ways to Remove Nitrogen Denitrification = Nitrate is converted to nitrogen gas by facultative / anaerobic bacteria. Nitrification = Ammonia is converted to nitrate aerobically. 1) Nitrosomonas bacteria convert ammonia to nitrite. 2) Nitrobacter bacteria convert nitrite to nitrate Nitrogen Uptake = Nitrogen is used for biological processes as part of floral & fauna cycles

67 Denitrification There are several factors which govern denitrification: 1. Presence of nitrate or nitrite 2. Absence of dissolved oxygen 3. Facultative bacteria mass that uses nitrate in place of oxygen as the electron acceptor 4. Presence of suitable electron donor Most commonly carbon, manganese, iron, & sulfur Can be accomplished by autotrophic & heterotrophic

68 Denitrification

69 Nitrification There are several factors which govern nitrification: 1. Occurs aerobically when dissolved oxygen is greater than 1 mg/l (4.6 PPD O2 / PPD NH3) 2. Requires long retention time 3. Low food to microorganism ratio 4. High mean cell residence time 5. Adequate Alkalinity *Plug flow aerated basins are ideal

70 Nitrification

71 The Advanced Aerated Lagoon Combines effective aeration with the latest pre & post treatment technologies Algae is mitigated via floating or fixed cover(s) Tertiary filtration is achieved by forcing the wastewater through sand / rock / media filters, prior to disinfection Disinfection requirements are minimized due to excellent treatment in the aerated lagoon itself Energy efficient blowers provide a short return on investment

72 Pre-treatment Keeping non-organic items out of lagoons is very important to long-term treatment success Baby-wipes in particular have become VERY problematic Grit removal systems should also be considered if If I&I is an issue, fixing old piping should be prioritized

Post Treatment Filtering wastewater through various types of media provides excellent removal of BOD, TSS, & NH3 Aerated rock or media filters have

73 Post Treatment Filtering wastewater through various types of media provides excellent removal of BOD, TSS, & NH3 Aerated rock or media filters have proven effective at polishing NH3 to low single digits P removal is typically preformed via in-situ chemical addition Recirculation offers many benefits

Covers & Algae Single cellular algae, especially duckweed can assist with blocking out sunlight and improving treatment achieved Multi cellular algae has a

74 Covers & Algae Single cellular algae, especially duckweed can assist with blocking out sunlight and improving treatment achieved Multi cellular algae has a tendency to increase TSS and cause issues with both aeration and disinfection Covering tertiary lagoons for ~ 5 days blocks sunlight, preventing algal formation

75 Disinfection Properly aerated lagoons provide a decent level of disinfection via oxidation and mixing 2 options commonly used 1) Chlorine 2) UV There are several advantages and disadvantages with each technique

76 Bunker Hill, IL - Advanced Aerated Lagoon Data

77 Keys To Wastewater Treatment 1) Quantify 2) Analyze 3) Implement Maintain ecological balance Pretreatment is critical (no inorganics) Understand oxygenation & mixing goals Design for the future using efficient technologies Complete system approach Evaluate & incorporate nutrient removal & recirculation Measure sludge every 3 5 years & have a mitigation plan in place

78 Questions?

WASTEWATER TREATMENT SYSTEM

WASTEWATER TREATMENT SYSTEM PrintStudioOne.com Nelson Environmental Inc. The Nelson Environmental OPTAER system is an efficient pond-based wastewater treatment solution utilized in a broad spectrum of