Presentation on theme: "How OWTSs Using Aerobic Treatment Work Texas AgriLife Extension Sevice."— Presentation transcript:
How OWTSs Using Aerobic Treatment Work Texas AgriLife Extension Sevice
Overview Treatment Processes Components of an OWTS using Aerobic Treatment, Disinfection and Spray Dispersal What is a Flow Equalization Tank?
Aerobic Treatment Unit System
Wastewater Treatment Processes Oxygen state Aerobic vs. Anaerobic Aerobic vs. Anaerobic Processes Physical Physical Chemical Chemical Biological Biological
Aerobic Aerobic bacteria require O 2 to live and grow Aerobic bacteria require O 2 to live and grow Aerobic treatment processes require O 2 to proceed Aerobic treatment processes require O 2 to proceed Common condition in soil treatment, media filters, MATUs Common condition in soil treatment, media filters, MATUs Anaerobic Anaerobic bacteria grow in absence of free oxygen,O 2 Anaerobic bacteria grow in absence of free oxygen,O 2 Anaerobic treatment processes do not use oxygen, but consumption of items, breaks oxygen bonds Ex. SO 4, NO 3 Anaerobic treatment processes do not use oxygen, but consumption of items, breaks oxygen bonds Ex. SO 4, NO 3 Common condition in septic tanks, processing tanks, and usually any saturated environment Common condition in septic tanks, processing tanks, and usually any saturated environment Aerobic vs. Anaerobic Processes (???)
Juvenile Rotifers Feeding on Rod-Shaped Bacteria pH 7.04 DO 1.2 ppm
Large Rotifers Attached to Aerobic Treatment Media Feeding on Bacteria & Organic Nutrients pH 6.94, DO 4.54 ppm
Mite on Aerobic Treatment Media pH 6.94, DO 4.54
Aerobic Treatment Unit System for a Residence
ATU, Disinfection and Spray Distribution System Components Septic/Trash tank Aerobic Treatment Air Supply Clarification Sludge Return Disinfection Pump tank with pump and controls Spray field
Septic / Trash Tank
Septic/Trash Tanks Most common treatment system: Water tight tanks. Water tight tanks. Anaerobic Treatment. Anaerobic Treatment. Most common treatment device. Most common treatment device. Septic tank: Minimum of two compartments Septic tank: Minimum of two compartments Trash tank: Typically smaller with one compartment Trash tank: Typically smaller with one compartment Some systems do not have a trash tank.
Two-Compartment Septic Tank
Septic Tank Treatment Process Physical separation processes – Settling of heavy materials – sludge layer Settling of heavy materials – sludge layer Floating of lighter materials – scum layer Floating of lighter materials – scum layer Clear zone (clear layer) Clear zone (clear layer) Effluent screen to assist in trapping solids (septic tank) Effluent screen to assist in trapping solids (septic tank) Time is the main requirement to allow separation to occur Detention time: Detention time: Septic tank - 2-3 daysSeptic tank - 2-3 days Trash tank – 1 dayTrash tank – 1 day Distance between inlet/outlet baffles is critical Distance between inlet/outlet baffles is critical Calm conditions to prevent mixing in the tank Anaerobic digestion and storage of materials until the tank is pumped
Aerobic Treatment Aeration Chamber
Aerobic Treatment Process Aerobic microbes digest solids Organic matter + O 2 = CO 2 + H 2 O + new cells Organic matter + O 2 = CO 2 + H 2 O + new cells Sludge accumulates in tank Extended aeration High DO, Long detention, Low Food/Microorganisms ratio High DO, Long detention, Low Food/Microorganisms ratio Organic matter to microbes, microbes eat each other, result in sludge Organic matter to microbes, microbes eat each other, result in sludge
Suspended Growth Aerobic microbes free swimming in the aeration chamber Mixing in the chamber mixes the microbes and the wastewater contaminants Extended aeration to limit biomass wasting
Submerged Attached Growth/Fixed Film Media Media is submerged in the aeration chamber Microbes are attached to the media Effluent is circulated through the media thus passing contaminants by the microbes Extended aeration to limit biomass wasting
Suspended Growth Configurations Should be three chambers/tanks. Single tank with three compartments. Multiple tanks. May combine aeration and clarification chamber with divider
Attached Growth Configurations Most have three chambers May be a separate media filled insert May have media placed in the aeration chamber Check manufacturer literature
Aeration of Wastewater Air is 21% oxygen Oxygen must transfer to wastewater for DO Quantity of oxygen transferred directly related to BOD removal Mixing of sewage
Aspirator/Aerator Vacuum pulls air into the water Spinning shaft or impeller causes the vacuum Limited resistance
Compressors Greater pressure Lower air flow Two distinct types of compressors Rotary Rotary Linear Linear Air inlet Housing - cover Rotary Linear
Compressor Air Flow Rotary compressor - Relatively straight increase in flow with a decrease in pressure Linear compressor – rapid decrease with increasing pressure Flow drops with resistance to air flow Flow drops with resistance to air flow Must have the correct compressor to have the correct air flow Rotary Linear
Blowers Greater air flow Lower pressure Air inlet screens/filters Air flow discharge from unit Larger pipe Air flow stops sharply Cannot operate under higher pressure
Air Distribution Lines Minimize friction loss in the distribution lines: Proper pipe diameter Reasonable distance between aerator and aeration chamber Minimize number of fittings (changes in direction) in the line.
Air Diffusion Porous Stone Diffuser Perforated Pipe
Clarification Process occurs in a “clarifier” Clarification is the process were the microbes, cell waste and biomass settle out of the water. Sludge blanket in the bottom and a clear zone below the discharge point
Vertical Settling Chamber Calm Environment Particles of Sufficient size and mass to settle Flow dependent Upward flow rate must be less than the settling rate
Configurations Separate chamber with no extra filtration Cone inserted into aeration chamber Many have sloped walls Added tertiary filter or screen in clarifier Filtration through socks placed in the aeration chamber Added filtration improves quality but increases maintenance
Flow Equalization Tank
Controlling Flow from a Residence Owner controls water usage to match clarifier capacity No large water using devices 500 gpd ATU has a max of 42 gph without flow equalization Or Install larger capacity system
Flow Equalization/Surge Tank Concepts Moderate Flow Daily fluctuations Daily fluctuations Weekly fluctuations Weekly fluctuations Down stream components Function more effectively Function more effectively May allow decrease size May allow decrease size Timer controls dosing to ATU
Flow Equalization/Surge Tank
Incorporating Flow Equalization Modify the treatment train by adding components Add an additional tank between the trash tank and aeration chamber Upsize trash tank to full size septic tank, add pump with timer controls to dose ATU
Sludge return Settled solids passing into a previous treatment chamber Passive system Settled solids passing through the bottom opening Most common method Active system Settled solids blanket below the outlet baffle
Disinfection, not Sterilization not Sterilization The goal of disinfection is to rid the wastewater stream of organisms capable of causing infection Sterilization is freeing the wastewater stream of ALL LIFE.
Chlorine Destroys target organisms by chemical oxidation of cellular material. Some organisms are resistant to low doses of chlorine Oocysts of Chrytosporidium parvum Cysts of Endamoeba histolytica Cysts of Giardia lamblia Eggs of parasitic worms
Chlorination Considerations Chlorine is an oxidizer. Need clean water (low BOD, low TSS): chlorine is not “stolen” to oxidize organic matter. Chlorine reacts with ammonia to form chloramines. Chloramines are not as effective as hypochlorous acid and hypochlorite ion for disinfection. Interferences: BOD, TSS, Humic Materials, Nitrite, pH, Iron, manganese and hydrogen sulfide
Dosing Dose = Concentration x Time Increasing either dosage or contact time, while decreasing the other, can achieve the same degree of disinfection. Breakpoint- the process where sufficient chlorine is added to the system to obtain a free chlorine residual
Caution People should be trained to properly handle and work with chlorine products High risk Exposure Exposure Handling Handling Corrosive Unstable Be careful where stored!!!!!!
Tablet Chlorination Tablet chlorinators generally have four components: Chlorine Tablets. Chlorine Tablets. A tube that holds the tablets. A tube that holds the tablets. A contact device, which puts the chlorine tablets into contact with the wastewater. A contact device, which puts the chlorine tablets into contact with the wastewater. A storage reservoir, usually a pump tank where the water is stored before it is distributed. A storage reservoir, usually a pump tank where the water is stored before it is distributed.
Typical Chlorine Tablets Wastewater tablets- Calcium Hypochlorite Basic compound – high pH Basic compound – high pH Swimming pool – Trichlorocyanuric acid Acidic compound – low pH Acidic compound – low pH Hazard to mix acids and bases Must use products in accordance with label
Residential Liquid Chlorination Flow passes through aspirator developing a vacuum or through a pump to draw a dose of chlorine. Tubing delivers chlorine dose to aspirator or pump Control volume of chlorine Mixing of chlorine with effluent in pump tank
Ultraviolet Light Disinfection Units UV light destroys microorganisms by altering their genetic material and / or retarding their ability to reproduce
Ultraviolet Light Disinfection Units Electromagnetic energy (UV light) from source lamp is emitted into a chamber through which effluent passes
Other Interferences to Effective UV Disinfection Dissolved organic compounds (BOD, TOC, COD) Organic iron compounds Humic compounds (tannins) Inorganic coatings on protective tubes
Pump Tank with Pumps and Controls
Pump Tank & Pump Stores water until time for dosing effluent Acts as storage for disinfection Storage capacity when system breaks Pump Type: effluent or sewage Type: effluent or sewage Not a grinder or sump Not a grinder or sump Specific flow & pressure Specific flow & pressure
Panel & Electrical Control Circuits Panel is a housing for components needed to control a system. Record valuable operational information Provide a means to collect operational data on the system Timer for night spray Timer for flow equalization Audio and visual alarms Power must be ON!
Lawn Sprinkler systems? --- NO!!! Spray treated wastewater over the surface of a yard Requires greatest level of treatment High risk system!!!!
Water Quality High potential for human contact with water Secondary- Quality Effluent Remove 85-98% of solids and organic matter Remove pathogens? Nutrients (nitrogen and phosphorus) are not required to be removed Soil for Final Treatment
Role of vegetative cover in treatment system A healthy cover crop is essential for the system to function properly. Plants will: Take up nutrients Take up nutrients Take up water Take up water Stabilize the soil and prevent erosion Stabilize the soil and prevent erosion Provide food and habitat for beneficial soil organisms Provide food and habitat for beneficial soil organisms Soil microbes are the final treatment!!!! This is effluent – NOT DRINKING WATER!!!! This is effluent – NOT DRINKING WATER!!!!
Connecting Distribution Heads to Laterals
Summary Treatment requirements Components of an OWTS using Aerobic Treatment, Disinfection and Spray Dispersal What is a Flow Equalization Tank?