Intensification of Algal Bioprocesses for Nutrient Recovery from Wastewaters

Jeremy GuestAssistant ProfessorCivil & Environmental EngineeringUniversity of Illinois at Urbana-Champaign

68th Annual KU Environmental Engineering ConferenceLawrence, KS

April 18, 2018

We may often think of algae as a potential risk to public and environmental health.

[green-blog.org]

[http://www.nsf.gov/news]

We may often think of algae as a potential risk to public and environmental health.

[toledoblade.com; 2014 water crisis]

cyanobacteria in Lake Erie near the drinking water intake for Toledo, Ohio

Note: Algae are eukaryotes. Cyanobacteria are often referred to as “blue-green algae”, but they are not algae. They are bacteria.

We may often think of algae as a potential risk to public and environmental health.

[toledoblade.com; 2014 water crisis]

the cyanobacteria bloom resulted in high concentrations of microcystin, a chemical that can damage the liver.

Or perhaps we think of algae as a nuisance…

[Kuldip Kumar, Metropolitan Water Reclamation District of Greater Chicago]

algae on secondary clarifier weirs can slough off and interfere with water quality measurements.

Today we’ll discuss the development of suspended growthalgal processes for wastewater treatment.

intensification of algal systems for nutrient recovery

traditional design and use of algal systems

recent findings and & emerging trends in algal processes

Phototrophs have traditionally been used in low intensity, large footprint systems like ponds or lagoons.

Wastewater ponds/lagoons are some of the most common technologies for small utilities.

[Data from Robert Bastian, US EPA; Algae Biomass Summit (ABS) Presentation, October 2016, Pheonix, AZ.]

In the U.S. in the year 2000:

~16,255 Publicly Owned Treatment Works (POTWs)

~ half (50.3%) included ponds/lagoons

~ half (49.7%) with no ponds/lagoons

The objective for microalgae in stabilization ponds has been to provide oxygen for BOD removal (and nitrification).

[Oswald and Gotaas (1957) Proc. Am. Soc. Civil Engrs., Separate; 686.]

Algae growth was largely incidental. Make the pond large and shallow, and algae will come (in low concentrations).

Design standards for ponds are empirical, based on depth and hydraulic retention time (HRT).

anaerobic facultative maturation(tertiary)

aerated

[Rich, Unit Processes of Sanitary Engineering, 1963]

anaerobic

facultative

maturation(tertiary)

aerated cBOD removalnitrification

cBOD removal nitrification

cBOD removal

cBOD removal

[Mihelcic et al., Field Guide to Environmental Engineering for Development Workers, 2009]

[Tchobanoglous et al., Wastewater Engineering: Treatment and Resource Recovery, 2014]

Design standards for ponds are empirical, based on depth and hydraulic retention time (HRT).

function

varies

1-1.5 m

1.2-2.4 m

2-5 m

depth

> 3 days

> 4 days

> 1 day

HRT

varies

These low(er) cost systems have been effective for many utilities with low flow and adequate land.

[maps.google.com]

…but conventional ponds simply haven’t evolved to meet the needs of many utilities.

reliable, resilient treatmentdespite influent microbes and changes in weather, wastewater composition & flow,

etc., MUST meet permits

small footprint

financially viable with manageable risk profile

[maps.google.com]

requirements for broader adoption of algal technologies

these objectives not met by ponds

nutrient removal or recovery

Intensification may make the technology a viable alternative for more utilities.

[maps.google.com]

[et.byu.edu]

[Clearas Water Recovery]

low intensitylarge footprint

medium intensitymedium footprint

high intensitysmall footprint

Two things to keep in mind for intensification: (i) algae achieve nutrient removal via growth and (ii) they can remove many forms of N and P.

N and P uptake via assimilation

N

P

N and P uptake via assimilation

NP

[Qin et al. (2015) Sci. Total Environ. 511, 47–53.]

access organic N/P

Two things to keep in mind for intensification: (i) algae achieve nutrient removal via growth and (ii) they can remove many forms of N and P.

traditional design and use of algal systems

recent findings and & emerging trends in algal processes

intensification of algal systems for nutrient recovery

Today we’ll discuss the development of suspended growthalgal processes for wastewater treatment.

To address needs for nutrient removal, algal turf scrubbers have been around for decades.

20[Adey, W.H. et al. Bioscience (2011) 61(6), 434-441]

[hydromentia.com]

Attached growth systems are mostly at the scale of a single greenhouse.

[http://www.algaewheel.com/]

In general, suspended growth phototrophic systems with good mixing achieve better treatment.

[Shoener et al. (2014) Environmental Science: Processes & Impacts; 16(6): 1204-1222]

HRAP - high rate algal pond (suspended)PBR - photobioreactor (suspended)Stirred Tank - stirred tank reactor (suspended)WSP - waste stabilization pond (suspended)ATS - algal turf scrubber (attached)

Recent efforts to intensify algal processes and achieve nutrient removal still rely on conventional assumptions.

HRT = SRT

typical assumptions

no solid-liquid separation to retain

biomass in the system

fixed N:P ratiosRedfield ratioC106N16P

N:P = 16:1

orspecies-specific

N:P

we cannot control what grows

it’s just a “bloom”

High rate algal ponds achieve more rapid nutrient recovery (relative to unmixed ponds).

[et.byu.edu]

High rate algal ponds are the most common approach to intensification of suspended growth processes.

[Frank Rogalla, Aqualia; ABS Presentation, October 2016]

pilot-scale plant recently built in Cadiz, Spain.

Small-scale high rate algal ponds are also being tested at pilot-scale at treatment plants in the U.S.

[microbioengineering.com/products]

Photobioreactors can further intensify treatment and have been pursued at pilot-scale.

[Rodolfi et al., Biotech Bioeng 102(1), 2009]

[chemicals-technology.com] [sardi.sa.gov.au]

[bae.uky.edu]

At least one photobioreactor system will be operating at full-scale in the United States in 2019.

Intensification is being enabled by solid-liquid separation using membranes.

These processes have the potential to achieve tertiary or sidestream nutrient recovery.

Tertiary Treatment

These processes have the potential to achieve tertiary or sidestream nutrient recovery.

Tertiary Treatment

Sidestream Treatment

intensification of algal systems for nutrient recovery

traditional design and use of algal systems

recent findings and & emerging trends in algal processes

Today we’ll discuss the development of suspended growthalgal processes for wastewater treatment.

Our approach to the intensification of algal processes is to challenge all of these assumptions.

HRT = SRT

typical assumptions

no solid-liquid separation to retain

biomass in the system

fixed N:P ratiosRedfield ratioC106N16P

N:P = 16:1

orspecies-specific

N:P

we cannot control what grows

it’s just a “bloom”

Our approach to the intensification of algal processes is to challenge all of these assumptions.

HRT = SRTtypical assumptionsfixed N:P ratios we cannot control

what grows

opportunities for innovationselective pressures

can enable reliabilityHRT << SRT

[Terry et al. (1985) J. Phycol. 21, 323–329.; Ågren (2004) Ecol. Lett. 7, 185–191.]

N:P is dependent on species & growth rate

We conduct experimental studies with real and synthetic wastewater, pure and mixed cultures, etc.

35

We conduct experimental studies with real and synthetic wastewater, pure and mixed cultures, etc.

1st thing to know: The N:P uptake ratio of algae can be influenced by controlling growth rate (via solids residence time, SRT).

[Gardner-Dale, D.A.; Bradley, I.M.; Guest, J.S. Influence of solids residence time and carbon storage on nitrogen and phosphorus recovery by microalgae across diel cycles. Water Research, 2017, 121: 231-239.]

2nd thing to know: Algae can take up nutrients at night by using intracellular, stored organic carbon.

[Gardner-Dale, D.A.; Bradley, I.M.; Guest, J.S. Influence of solids residence time and carbon storage on nitrogen and phosphorus recovery by microalgae across diel cycles. Water Research, 2017, 121: 231-239.]

3rd thing to know: You may be able to achieve reliable performance with your local algae.

39[Fedders, A.C.; DeBellis, J.L.; Bradley, I.M.; Sevillano-Rivera, M.C.; Pinto, A.J.; Guest, J.S. Comparable nutrient uptake across diel cycles from three distinct algal communities. Submitted]

FloridaIllinois North Carolina

4th thing to know: We will be able to model algae just as well as every other wastewater treatment process.

41

[Guest, J.S.; van Loosdrecht, M.C.M.; Skerlos, S.J.; Love, N.G. A lumped pathway metabolic model of organic carbon accumulationand mobilization by the alga Chlamydomonas reinhardtii. Environmental Science & Technology, 2013, 47(7), 3258-3267.]

4th thing to know: We will be able to model algae just as well as every other wastewater treatment process.

42

use whole-plant, dynamic models

add in algal unit processes with the phototrophic process model (PPM)

ASMs, ADM1, Mantis, phys-chem models

[Guest, J.S.; van Loosdrecht, M.C.M.; Skerlos, S.J.; Love, N.G. A lumped pathway metabolic model of organic carbon accumulation and mobilization by the alga Chlamydomonas reinhardtii. Environmental Science & Technology, 2013, 47(7), 3258-3267.]

[Shoener et al. (Work in progress).]

To summarize our recent findings: there’s a bright future for intensive algal treatment processes. We will…

tailor N:P uptake to match your wastewater

achieve 24-hr nutrient uptake via stored carbon

leverage local algae model these processes and their integration into the plant

There’s a bright future for intensive algal treatment processes.

tailor N:P uptake to match your wastewater

achieve 24-hr nutrient uptake via stored carbon

leverage local algae

model these processes and their integration into the plant

Jeremy Guest, Assistant Professorjsguest@illinois.edu

In the not-to-distant future, you’ll be able to:

tertiary

sidestream