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Tech 110: Pretreatment Technologies. Between the tank and the soil. Overview of Pretreatment. Adapted from The University Curriculum for Decentralized Wastewater Management Prepared by: John R. Buchanan, Univ. of TN; Robert W. Seabloom, Univ. of WA; Dave Lenning, Alternatives Northwest

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tech 110 pretreatment technologies

Tech 110:Pretreatment Technologies

Between the tank and the soil

overview of pretreatment

Overview of Pretreatment

Adapted from The University Curriculum for Decentralized Wastewater Management

Prepared by: John R. Buchanan, Univ. of TN;

Robert W. Seabloom, Univ. of WA;

Dave Lenning, Alternatives Northwest

Edited by: David Lindbo and Nancy Deal, NCSU

slide3

NDWRCDP DisclaimerThis work was supported by the National Decentralized Water Resources Capacity Development Project (NDWRCDP) with funding provided by the U.S. Environmental Protection Agency through a Cooperative Agreement (EPA No. CR827881-01-0) with Washington University in St. Louis. These materials have not been reviewed by the U.S. Environmental Protection Agency. These materials have been reviewed by representatives of the NDWRCDP. The contents of these materials do not necessarily reflect the views and policies of the NDWRCDP, Washington University, or the U.S. Environmental Protection Agency, nor does the mention of trade names or commercial products constitute their endorsement or recommendation for use.

cidwt university disclaimer
CIDWT/University Disclaimer

These materials are the collective effort of individuals from academic, regulatory, and private sectors of the onsite/decentralized wastewater industry. These materials have been peer-reviewed and represent the current state of knowledge/science in this field. They were developed through a series of writing and review meetings with the goal of formulating a consensus on the materials presented. These materials do not necessarily reflect the views and policies of University of Arkansas, and/or the Consortium of Institutes for Decentralized Wastewater Treatment (CIDWT). The mention of trade names or commercial products does not constitute an endorsement or recommendation for use from these individuals or entities, nor does it constitute criticism for similar ones not mentioned.

cidwt university disclaimer1
CIDWT/University Disclaimer

These materials are the collective effort of individuals from academic, regulatory, and private sectors of the onsite/decentralized wastewater industry. These materials have been peer-reviewed and represent the current state of knowledge/science in this field. They were developed through a series of writing and review meetings with the goal of formulating a consensus on the materials presented. These materials do not necessarily reflect the views and policies of North Carolina State University, and/or the Consortium of Institutes for Decentralized Wastewater Treatment (CIDWT). The mention of trade names or commercial products does not constitute an endorsement or recommendation for use from these individuals or entities, nor does it constitute criticism for similar ones not mentioned.

why pretreat
Why Pretreat?

“Pretreat” wastewater so downstream component(s) can function more reliably for longer terms

pretreatment options
Pretreatment Options
  • Traditionally, have been categorized as:
    • Primary – solids removal
    • Secondary –organics and BOD removal
    • Tertiary – generally, nutrient removal
  • Microbes typically used to assist
    • Aerobic
    • Anaerobic
    • Facultative
  • Aerobic and anaerobic processes are compatible
primary treatment
Primary treatment
  • Septic tanks
  • Grease traps
  • Grease interceptors
primary treatment septic tanks
Primary treatment: Septic tanks
  • Functions
    • Separate solids from liquid
    • Anaerobic decomposition
    • Attenuate surges
    • Ventilation
primary treatment septic tanks1
Primary treatment: Septic tanks
  • Most common unit for OWTS
  • Used alone or with other pretreatment units
  • Simple and generally inexpensive ($100s)
  • 30-50% reduction BOD5, 60-80% reduction TSS
primary treatment grease traps
Primary treatment: Grease traps
  • Function
    • Remove grease and oils
    • Used where greases/oils expected (usually commercial sites like restaurants)
    • Does not normally receive blackwater
primary treatment grease separators
Primary treatment: grease separators
  • Typically, proprietary products
  • High maintenance products
  • Historically, not good performance because of poor maintenance
advanced pretreatment
Advanced pretreatment
  • Secondary treatment
    • TSS and BOD removal
    • Microbes typically used to assist
      • Aerobic
      • Anaerobic
      • Facultative
secondary treatment
Secondary treatment
  • Use aerobic microorganisms to provide secondary treatment to domestic wastewater
    • Focuses on removal of biodegradable organics and suspended solids
    • Convert soluble particulates to insoluble ones so we can remove them
    • usually accomplished with biological reactors
  • Biodegradable organics must be removed to minimize impact on subsequent processes
aerobic reactions
Aerobic reactions
  • If enough dissolved O2 is in the effluent then the effluent is Aerobic
    • O2 > 1.0 ppm
  • Bacteria break down waste constituents under these conditions
nitrification
Nitrification

NO2

NH3

H2O

O2

NO2

NO3

O2

providing dissolved oxygen do
Providing Dissolved Oxygen (DO)
  • Advanced treatment systems are designed to provide lots of DO
    • high-rate carbon removal and ammonification
    • occupies a small-footprint
    • requires energy to maximize oxygen transfer
    • biological reactor
slide19
BOD
  • Often used as a measure of wastewater strength
    • a high BOD suggests that the organic compounds are easily biodegradable
    • indicates the mass of dissolved oxygen that could be removed by aerobic microbes as they metabolize
  • Secondary treatment devices reduce the oxygen demand of a wastewater
advanced pretreatment1
Advanced pretreatment
  • Tertiary treatment
    • Generally, nutrient removal
    • Disinfection
anoxic anerobic reactions
Anoxic/anerobic reactions
  • If all O2 is low effluent becomes anoxic/anaerobic
    • O2 < 0.5 ppm
denitrification
Denitrification

CO2

NO3

N2 gas

optimizing a natural process
Optimizing a natural process
  • Bioreactors are built to maximize the production of beneficial end-products
    • alcohols (beer, wine)
    • insulin
    • other medications
  • And
    • Renovate wastewater
the good bugs
The good bugs
  • Convert colloidal and dissolved carbonaceous organic matter into various gases and into cell tissue
    • gases evolve (CO2, N2, and others)
    • new cells can settle – thus carbon is removed
  • Break other nutrients out of organic compounds
    • nitrogenous compounds
    • phosphorus species
the bad bugs
The bad bugs
  • Pathogens
    • Use disinfection to inactivate these
    • Generally UV, Chlorine
the soil
The soil…
  • Is a bioreactor too!
slide28

Shallow system = Aerobic treatment

Well

Aerobic soil needed for treatment

Groundwater

deep system less aerobic to anaerobic system
Deep system = Less aerobic to anaerobic system

Well

Low O2 results in less aerobic soil therefore treatment

Groundwater

advanced treatment
Advanced treatment
  • Lessens the burden placed on the soil
  • Allows use of less-than-optimum sites
    • Increased risk requires attention to O&M
wastewater treatment
Wastewater Treatment
  • Examples of Aerobic Bioreactors used for Secondary Treatment
    • activated sludge plants
    • rotating biological contactors
    • packed-bed media filters
  • Highly-engineered systems that utilize microbial metabolism to convert organic compounds into cells and carbon dioxide
environmental effects
Environmental Effects
  • Microbes need more than organic carbon, dissolved oxygen and water
    • need steady supply of food to maintain stable microbial population
    • pH needs to be monitored
      • low alkalinity can cause large changes in pH
    • Be careful with biocides
      • acid drain cleaner
      • antibiotics
environmental effects temperature
Environmental effects: Temperature
  • Overall, as temperature rises, microbial activity increases (but not too hot)
  • Microbes can be grouped by temperature preference
    • Psychrophilic microorganisms
      • optimum temperature 12° to 18° C
    • Mesophilic microorganisms
      • optimum temperature 25° to 40° C
    • Thermophilic microorganisms
      • optimum temperature 55° to 65° C
summary
Summary
  • Aerobic Treatment of Wastewater
    • takes advantage of a natural process
    • process can be easily engineered into a biological reactor for high-rate wastewater treatment
    • removes the oxygen demand from wastewater before being discharged back into the hydrologic cycle
  • Carbon is transformed into cell mass and into carbon dioxide
n cycle in septic systems
N Cycle in Septic Systems

Mineralization

Immobilization

Nitrification and Sorption

Denitrification ?