Chapter 12: Private Onsite Wastewater Treatment and Disposal

Onsite Wastewater Systems

-25% of U.S. Population served -Treats black water (toilet waste) and gray water (sinks, showers, laundry)

Soil Permeability: Percolation Tests

-A measure of the relatively constant rate at which clear water maintained at a relatively constant depth (6 in.) will seep out of standard sized test hole -primary sedimentation can remove in soil, water, and wastewater: 50-90% bacteria 30-50% ascaris 80% schistosomes

Sewage Treatment Processes

-Anaerobic digestion- no oxygen, slow process -Aerobic digestion- uses oxygen, rapid process -amount of dissolved oxygen required in aerobic bacterial decomposition, measure in ppm or mg/1 and used in determining strength of wastewater is biochemical oxygen demand -Facultative bacteria can live under aerobic and anaerobic condition

Stream Pollution

-Apparent by a zone of degradation

Water Softening Units

-Brine from water softening units as low as 1.2% may inhibit bacterial action in septic tanks

Execute the Percolation Test

-Dig 1'x1' hole to drain field depth (24"-30") -Drop in gravel to cover bottom (2") -Saturate hole: four hours & let swell overnight -Slowly pour 12" of clear water

Grease Trap

-Installed for the purpose of minimizing grease in sewer system. The trap is not of proven value in commercial applications

Septic Tank Absorption Field System

-Limitation of use is due to soil type and size requirements

Refractory Organics

-Man-made organic compounds that degrade slowly

Perc Test Calculations

-Perform at least 3 test for the ave lot -6 tests preferred soil is not relatively uniform -Small subdivision: 3 test holes per acre; more holes if samples vary by 20% -Finish by digging 1 hole at least 4-6 feet to determine separation distance to limiting layer -NOT suitable if limiting layer is w/in 4 feet

Proper Wastewater Disposal Criteria

-Prevention of human waste & toxic chemicals contacting or being exposed on the ground surface

The NODAK system is designed to

-Protect ground water

Unsuitable Soil

-Sand filters, elevated system in suitable fill, evapotranspiration absorption systems and beds, aeration systems, stabilization ponds or lagoons and recirculating toilets are used

Interpreting Percolation Tests

-Soil saturation is critical -Interpretation of results highly variable

Absorption Field

-Top travel should be covered with permeable material -Field distribution piping should be surrounded with washed gravel, 3/4 inches to 2 1/2 inches

Seepage Trench

-Trench width 12-24", no more than 24"

Plants

-Trickling filters, activated sludge, and spray irrigation cause health hazards due to inhalation of airborne microorganism -Absorb certain constituents of wastewater; using wastewater for irrigation of consumable plant produce may present health hazard of water contains cadmium

Imhoff Tanks

-Used for sewage disposal are primarily dependent upon action of bacterial decomposition

Soil Characteristics & Clues

-Yellow, brown, or red- air & water passes thru -Blue or grey- saturated for long period of time -Mottled broke or red- fluctuating seasonal high water table, unsuitable for substance absorption of wastewater lack of aeration -Greyish- iffy, but generally unstable also

Disease Hazards

-assume that all sewage contains pathogenic organisms -pathogenic organisms can survive on soil less than a day to more than 2 years -main indicator organism in segue is Escherichia coli (fecal coliform) -no process other than disinfection can remove all pathogens -most important factor contributing to disease transmission of microbiological agent is concentration or dose of microorganisms

Hydrogen Sulfide is fatal

-at concentrations of 300ppm

Trickling Filters

-can remove 90-95% of bacteria, viruses, and vibrio cholera found in soil, water, and wastewater

Not Explosive Component of Sewer Gas

-carbon dioxide

Inlet & Outlet Baffles & Tees and Effluent

-inlet/outlet baffle elevation differential 3 inches -disinfection or chlorination of sewage effluent is an added safeguard to reduce risk of disease transmission -USEPA standards, pH of secondary effluent must be 6-9

Nonpoint Pollution

-not a point source & is manmade/man-induced resulting in alteration of chemical, physical, biological, or radiological integrity of water

Clostridium perfringens

-second word of name indicates species

Suspended Solids

-solids visible in suspended water -test is retention on asbestos mat in a Gooch crucible (way of measure) and represent food that bacteria eat

Combined Sewer

-storm water & domestic sewage are combined in same pipe -most accurate estimates of sewage flow are based on annual water-meter readings

Permissible 8 Hour Threshold Limit Value of H2S

20 ppm

Common Sewage-Borne Disease- Protozan

Amoebiasis Giardiasis Balantidiasis Cryptosporidium (N. Fowler)

Common Sewage-Borne Disease- Helminthes

Ascariasis Taeniasis Dracunculiasis (Schistosoma m.)

Balantidiasis

Balantidium coli Protozoan infection of colon Waterborne epidemics occur in poor fecal sanitation

Oxygen Demand Definitions

Biochemical Oxygen Demand (BOD)- Usually 5 days. It is the best single measure of wastewater or polluted water -used to conduct series of tests to,determine degree of water pollution -samples refrigerates and analyzed within hours Chemical Oxygen Demand (COD)- Good for measuring industrial wastes

Campylobacter Jejuni

Can trigger Guillain-Barré syndrome

Salmonellosis

Disaster implications - caution during mass feedings

Sewage Protozoal Organisms

Giardia lamblia Taenia saginata & T. Solium Entamoeba histolytica Balantidium coli

Soil Characteristics

Gravel (greater than 2mm) Sand (2mm to 0.05mm) Silt (0.25mm to 0.002mm) Clay (less than 0.002mm)- smallest Loam soil- sand, silt, clay (ideal % = 40/40/20) -loam contains decayed plant and animal matter

Common Sewage-Borne Disease-Viral

HAV HRV Adenovirus Enterovirus- poliovirus, coxsackle Norwalk

Causes of System Failure

Hydraulic overload- seasonal high water table (floating septic tank) System damage- soil compaction in absorption area

Common Sewage-Borne Disease Spirochete Bacteria

Leptospirosis

Raw Sewage Emergency Treatment

Lime treatment -Estimate gallons: length x width x ave depth x 7.5 -Apply 20 to 25 pounds per 1000 gallons -Confirm by testing pH pH 12.0 or higher 30 minute minimum duration contact time

Ideal On-Site Wastewater Treatment (Best)

Mini-treatment plant -primary sedimentation -secondary treatment -tertiary treatment -chlorinate -de-chlorinate

Bio solids Disposl: Land Application

No application within 24 hours of rain No application in winter No pounding of biosolids Maximum application rate of 2,500 gallons per acre per day Lime stabilized Must keep extensive records -most common method for applying wastewater to land is spray irrigation

Spirochete Bacterial Disease

Occupational hazard to rice & sugarcane field workers & other fresh water jobs

Ancylostomiasis

Prevention- sanitary sewage disposal & shoes (typical in south)

How does the septic tank work?

Purpose- 24-72 hour watertight detention tank -condition sewage to be more readily percolated into the subsoil Functions- removal of solids -biological treatment -sludge & scum storage -If septic tank will have a garbage disposal unit feeding it the size of tank should be increased 50% -Septic tanks serving commercial operations must be inspected for cleaning twice per year -Septic tank cleaners are not advised and nothing (chemicals) should be added

Design Flow

Residential- usually based on number of bedrooms -sometimes based on fixtures

Trichuriasis

Roundworm (whipworm) infection Transmission- colon

Common Sewage-Borne Disease- Bacterial

Shigellosis Salmonella- typhoid fever, paratyphoid fever, salmonellosis Campylobacter Enteritis Diarrheagenic E. coli- Enterotoxigenic (ETEC), Enteropathogenic (EPEC), Enteoinvasive (EIEC), Enteroaggregative (EAggEC) Cholera Yersiniosis Enterohemorrhagic (EHEC) 0157:H7 (STEC)

Maintenance

Sludge management: -septic tank- inspected annually, clean at least every 3 years or sooner

Taeniasis

Transmission (larval cysts) Sewage involvement- keep cattle & swine away from human feces

Septic Tank bio-solids Disposal

Two main means of disposal: 1. Sewage treatment plant 2. Land disposal -Deep sludge depth, thick fog layer, and appearance of particles of solids in effluent from septic tank indicate septic tank inn need of cleaning

Reclaimed Water Usage

Unapproved Usages -body contact recreation -cooking or drinking -irrigating vegetable and herb gardens