a new approach to biological phosphorus removal

BUILDING A WORLD OF DIFFERENCE®

WEFTEC 2010

TS002: Secondary Phosphorus RemovalTS002: Secondary Phosphorus Removal

J. Barnard, D. Houweling, H. Analla, M. Steichen

A New Approach to Biological Phosphorus Removal

TS002: Secondary Phosphorus Removal

WEFTEC 2010

Overview

Introduction

Overview of unconventional phosphorus removal

Fermentation of RAS for phosphorus removal

Fermentation of mixed liquor for phosphorus removal

Models must simulate all observations

Summary


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Phostrip Process - 1965


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Anaerobic zone formed at inlet end of aeration basin

In the late 60’s phosphorus removal was observed in high rate plug-flow plants that did not nitrify. Milbury noted that all such plants showed a release of phosphorus at the feed end

Inefficient aeration and high oxygen demand

responsible


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Bardenpho Pilot plant (100 m3/d)

The purpose of the dead zone was to allow relative adjustments to the other zones.


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Static Fermenter

Anoxic

to digesters

anaerobic

VFAOptional recycle

PST


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Reedy Creek, Florida

0

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Tota

l P, m

g/L

First FewAerators Turned Off

Switching off Aerators - Disneyworld


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US Patent 5,603,833 POH process 1995

Claim required a retention time of 12 to 72 hours in Stressed Zone but does not refer to sludge settling. Reference to a side-stream

process for reduction of nitrates in the RAS.

Several patents


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Configuration proposed by Stroud et al for achieving both nitrogen and phosphorus removal

4Q

AX

AN

AER

Ferment

AX

AX

AEREffluent

WAS

Influent

Bardenpho plant

RAS Fermentation


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Conversion from Pho-strip to Phoredoxwith RAS fermentation

Aerated Settling

Effluent

Fermenter

Wasted Biomass

Return Biomass

Influent Wastewater

0.85 RAS

Anaerobic

0.15 RAS

Aerated Settling

Effluent

Stripper

WastedBiomass

Return Biomass

InfluentWastewater

Lime

LimeSludge


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Configuration used by Vollertsen for BPR

Anox/Aerobic

InfluentEffluent

Anaerobic zone

7% Return activated sludge

93%

The main reactor consisted of channel systems for SND. 7% of the RAS was passed to a sidestream anaerobic zone with long retention. Note that VFA in the feed was lost for enhancing phosphorus removal


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BPR Operation at St Cloud MN

Under-aeration


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Effluent Quality for the St Cloud MN plant2009 Effluent Nutrients in mg/L

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Eff CBOD5 Eff. TP TKN EFF NH3 EFF


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Mixed liquor Fermentation at Pinery Water

Anaerobic Anaerobic

Anoxic

OFF ON

Influent RAS

Aer

obic

Phosphorus reduced form 9 mg/L to less than 0.5 mg/L , then with post chemical treatment to less than 0.03 mg/L. Overall molar ratio to Al:P is 0.5


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Mixed liquor Fermentation at Henderson NV


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arou

selP

lant

Hen

ders

on N

V


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Results from Henderson NV

Ortho-P for May 2010

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Phos

phor

us (m

g/L)

ANA Eft SPS SCC Final Eft


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Surface appearance of Henderson Plant

Some hours after mixer off

During mixing


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Fermenting Mixed Liquor

PAO

VFA

PAO

PAO

PAO

PAO

VFA

Mixed Liquor

Mixed Liquor OutMixed Liquor In

Heterotrophes

In the mixed liquor fermenter, the PAO survive – the OHO are fermented to produce VFA

Barnard presentation Krakow 2007


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MJHB – UMIF Strategy

We propose that this be formalized in design to create an upflow mixed liquor fermenter attached to the anaerobic zone


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Application to Henderson plant


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What have we learned?

Phosphorus removal with unconventional processes can give reliable results

Mostly such phosphorus removal happened by manipulation or full-scale experimentation and not by design

There are too many unknowns for a lawyer-free design

Role of nitrates

Role of influent rbCOD

Solids retention time under fermentation

Portion of the mixed liquor that can be fermented

Temperature


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What is needed

A better understanding of mechanisms at play

Optimizing the configuration

Consider side stream fermentation of mixed liquor as opposed to RAS

Remove the chance aspect and have more control

Model the performance of these plants in order to design with confidence


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Challenge to the Proprietors of Simulation Models

Efforts to model unusual phosphorus removal configurations were at first, not successful

It may be necessary to change the basic structure of models to allow for the survival of the PAO

Attend follow up paper on Wednesday by Dwight Houweling for discussion on model application


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Modeling the pilot plant flow diagram


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Conclusion

Plants with some form of internal fermentation of mixed liquor or RAS can result in reliable biological phosphorus removal – There seems to be consensus that less than 10% of the return sludge should be fermented.

Plants that do not remove phosphorus reliably can be improved bymanipulating aeration

Future designs should optimize the configuration to make maximum use of internal fermentation of mixed liquor

Fermentation of mixed liquor as opposed to RAS seem to be superior especially in plants with no primaries

Efforts are under way to establish if UMIF can replace primary sludge fermenters or allow the products to be used for denitrification.


WEFTEC 2010

a new approach to biological phosphorus removal

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