Tech 110: Pretreatment Technologies Between the tank and the soil

Overview of Pretreatment Adapted from The University Curriculum for Decentralized Wastewater Management 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

NDWRCDP Disclaimer This 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. CR ) 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 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 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? “Pretreat” wastewater so downstream component(s) can function more reliably for longer terms

Pretreatment Options  Traditionally, have been categorized as: Primary – solids removal Primary – solids removal Secondary –organics and BOD removal Secondary –organics and BOD removal Tertiary – generally, nutrient removal Tertiary – generally, nutrient removal  Microbes typically used to assist Aerobic Aerobic Anaerobic Anaerobic Facultative Facultative  Aerobic and anaerobic processes are compatible

Primary treatment  Septic tanks  Grease traps  Grease interceptors

Primary treatment: Septic tanks  Functions Separate solids from liquid Separate solids from liquid Anaerobic decomposition Anaerobic decomposition Attenuate surges Attenuate surges Ventilation Ventilation

Primary treatment: Septic tanks  Most common unit for OWTS  Used alone or with other pretreatment units  Simple and generally inexpensive ($100s)  30-50% reduction BOD 5, 60-80% reduction TSS

Primary treatment: Grease traps  Function Remove grease and oils Remove grease and oils Used where greases/oils expected (usually commercial sites like restaurants) Used where greases/oils expected (usually commercial sites like restaurants) Does not normally receive blackwater Does not normally receive blackwater

Primary treatment: grease separators  Typically, proprietary products  High maintenance products  Historically, not good performance because of poor maintenance

Advanced pretreatment  Secondary treatment TSS and BOD removal TSS and BOD removal Microbes typically used to assist Microbes typically used to assist AerobicAerobic AnaerobicAnaerobic FacultativeFacultative

Secondary treatment  Use aerobic microorganisms to provide secondary treatment to domestic wastewater Focuses on removal of biodegradable organics and suspended solids Focuses on removal of biodegradable organics and suspended solids Convert soluble particulates to insoluble ones so we can remove them Convert soluble particulates to insoluble ones so we can remove them usually accomplished with biological reactors usually accomplished with biological reactors  Biodegradable organics must be removed to minimize impact on subsequent processes

Aerobic reactions  If enough dissolved O 2 is in the effluent then the effluent is Aerobic O 2 > 1.0 ppm O 2 > 1.0 ppm  Bacteria break down waste constituents under these conditions

Respiration CO 2 O2O2 H2OH2O

Nitrification NH 3 NO 2 NO 3 H2OH2O NO 2 O2O2 O2O2

Providing Dissolved Oxygen (DO)  Advanced treatment systems are designed to provide lots of DO high-rate carbon removal and ammonification high-rate carbon removal and ammonification occupies a small-footprint occupies a small-footprint requires energy to maximize oxygen transfer requires energy to maximize oxygen transfer biological reactor biological reactor

BOD  Often used as a measure of wastewater strength a high BOD suggests that the organic compounds are easily biodegradable 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 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 pretreatment  Tertiary treatment Generally, nutrient removal Generally, nutrient removal Disinfection Disinfection

Anoxic/anerobic reactions  If all O 2 is low effluent becomes anoxic/anaerobic O 2 < 0.5 ppmO 2 < 0.5 ppm

Denitrification N 2 gas NO 3 CO 2

It’s all about the bugs (Microbes)

Optimizing a natural process  Bioreactors are built to maximize the production of beneficial end-products alcohols (beer, wine) alcohols (beer, wine) insulin insulin other medications other medications  And Renovate wastewater Renovate wastewater

The good bugs  Convert colloidal and dissolved carbonaceous organic matter into various gases and into cell tissue gases evolve (CO 2, N 2, and others) gases evolve (CO 2, N 2, and others) new cells can settle – thus carbon is removed new cells can settle – thus carbon is removed  Break other nutrients out of organic compounds nitrogenous compounds nitrogenous compounds phosphorus species phosphorus species

The bad bugs  Pathogens Use disinfection to inactivate these Use disinfection to inactivate these Generally UV, Chlorine Generally UV, Chlorine

The soil…  Is a bioreactor too!

Groundwater Well Aerobic soil needed for treatment Shallow system = Aerobic treatment

Groundwater Well Low O 2 results in less aerobic soil therefore treatment Deep system = Less aerobic to anaerobic system

Advanced treatment  Lessens the burden placed on the soil  Allows use of less-than-optimum sites Increased risk requires attention to O&M Increased risk requires attention to O&M

Wastewater Treatment  Examples of Aerobic Bioreactors used for Secondary Treatment activated sludge plants activated sludge plants rotating biological contactors rotating biological contactors packed-bed media filters packed-bed media filters  Highly-engineered systems that utilize microbial metabolism to convert organic compounds into cells and carbon dioxide

Environmental Effects  Microbes need more than organic carbon, dissolved oxygen and water need steady supply of food to maintain stable microbial population need steady supply of food to maintain stable microbial population pH needs to be monitored pH needs to be monitored low alkalinity can cause large changes in pHlow alkalinity can cause large changes in pH Be careful with biocides Be careful with biocides acid drain cleaneracid drain cleaner antibioticsantibiotics

Environmental effects: Temperature  Overall, as temperature rises, microbial activity increases (but not too hot)  Microbes can be grouped by temperature preference Psychrophilic microorganisms Psychrophilic microorganisms optimum temperature 12° to 18° Coptimum temperature 12° to 18° C Mesophilic microorganisms Mesophilic microorganisms optimum temperature 25° to 40° Coptimum temperature 25° to 40° C Thermophilic microorganisms Thermophilic microorganisms optimum temperature 55° to 65° Coptimum temperature 55° to 65° C

Summary  Aerobic Treatment of Wastewater takes advantage of a natural process takes advantage of a natural process process can be easily engineered into a biological reactor for high-rate wastewater treatment 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 removes the oxygen demand from wastewater before being discharged back into the hydrologic cycle  Carbon is transformed into cell mass and into carbon dioxide

Questions?

N Cycle in Septic Systems Nitrification and Sorption Denitrification ? Mineralization Immobilization