Algal Turf Scrubber (ATS) - Environmental Science & Technology

129 Pages·2010·6.21 MB·English

Algal Turf Scrubber (ATS)

Algae to Ene rgy Project

Cleaning Rivers while Producing Biofuels
and
Agricultural and Health Products

Report to:
David Orr and Adam Lewis
The Lewis Foundation
% The Lipson Group Inc.
1422 Euclid Avenue, Suite 1500
Cleveland, OH 44115
January 31, 2010

Walter H. Adey
Department of Botany
National Museum of Natural History
Smithsonian Institution
Washington, D.C. 20560
[email protected]

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Table of Contents

Executive Summary

Introduction

The ATS Energy Project

The Algae
Primary Production
3-D Solution to the Diatom “problem”
The ATS Ecosystem
Nutrient Removal
Oxygen Injection
By-Products of ATS
The All-Terrain ATS
Issues to Consider

The Economics of ATS Operation

Plans for Project Expansion

References

Appendix
A. Algae of the Test Systems, Smithsonian Institution
B. Susquehanna Project, University of Maryland
C. Ozark Highlands Project, University of Arkansas
D. Biomass Processing, Western Michigan University
E. Project Extension (Chesapeake Algae Project, ChAP/Chesapeake Algae
Consortium): organizations listed above, plus
Blackrock Energy, StatoilHydro, Exelon Power, Constellation
Energy, HydroMentia, Ecological Systems Technology
University of William and Mary/VIMS,

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EXECUTIVE SUMMARY
Developed initially to control aquatic microcosms, Algal Turf Scrubbing (ATS)
has a 30-year history of integration with the chemical and biological function of
living ecosystems. Scaled-up, over the last 15 years, to several acre dimensions
for tertiary sewage treatment, aquaculture and remediation of eutrophic creeks
and canals, it has been used, coast to coast, in the southern U.S. The purpose of
this investigation, funded by the Lewis Foundation, was: (1) to expand ATS
technology to river scale, especially in more northerly climes; (2) to develop by-
products from ATS-produced algal biomass, including biofuels; and (3) to develop
the economics of large watershed application. To accomplish these tasks, several
test ATS floways have been established on rivers, and numerous working
associations with university scientific teams and companies have been developed.
The major finding of the field experimentation of this study on large non-
point-source waters was a shift of ATS community structure from a standing crop
dominance of filamentous green algae to that of filamentous diatoms. The
biodiversity of the ATS algal communities was thereby greatly increased,
enhancing the basic rationale of ATS. However, the lesser shear strength of
diatom filaments, in the moderate energy environment of ATS, increased slough
rate, and reduced expected productivity by 25-50% and nutrient removal by 10-
30%. This issue has been resolved with the development of a new type of basal,
3-D screen that retains diatoms, more than doubles algal productivity, and
produces an entirely new field of potential process improvement. While broader
use of this new technique is necessary, it is likely that further enhancement of
nutrient remediation is now possible. Interface Global has joined our team, and is
working to achieve mass production of these new screens; it seems likely that
cost increases will be minimal as compared to process enhancement.
Photosynthesis produces oxygen, and the experiments of this study have
emphasized that oxygen production by ATS is large; by manipulation of ATS flow
to prevent excess supersaturation, injection of more than 35 tons/ATS acre/year
into source waters should be possible. The more serious implication of water
body eutrophication is hypoxia (“dead zones”), and in watershed amelioration,
more emphasis needs to be placed on direct removal of hypoxia. This study
produces an initial plan to accomplish this task for Chesapeake Bay.
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Aliquots of the algal biomass produced on the ATS floways of this study
have been shipped to our associate team of chemists at Western Michigan
University, where they have developed a physical/chemical separation process for
carbohydrates, oils, proteins and minerals. The processed carbohydrate solutions
were forwarded to our associate chemical engineering team at the University of
Arkansas, where they have been converted to hydrogen and butanol using a
membrane-modified, double Clostridium fermentation. The W. Michigan team
has also demonstrated omega-3, PUFA’s in the ATS algal oils. While it seems likely
that omega-3 separation will be more economic than the transesterification to
biodiesel process that the Western Michigan team has also demonstrated, this
should be determined at pilot scale. In plant growth tests, the residual proteins
and minerals have been shown to be a quality fertilizer. However, the large
quantity of silica diatom frustules, with a very large surface/volume ratio, in the
mineral-rich fertilizer may additionally provide soil remediation that can lead to
significant capturing and storing of atmospheric carbon. Both chemistry teams
are now ready to begin expansion of this refinery process to pilot scale.
Previous large scale ATS systems have required time-consuming
construction, earth-moving, grading and surface-preparation methods that have
provided limitations to scale up. In this study, a new, at par cost, All-Terrain ATS
unit has been developed that provides for rapid construction, dimensional
flexibility, and applicability to unstable and difficult terrain such as landfills and
river bottomland. This system will be used extensively in planned watershed
scale-up.
With the development of an array of by-products, and the ability to work
quickly and at large scale on rivers, tributaries and bays, this project has
presented a preliminary economic plan for ATS utilization that can reduce the cost
of both water remediation and algal by-product production. In the under way
process of scale-up to pilot, and then full scale, for the Chesapeake Watershed, it
will be necessary to further enlist environmental economists and modelers to
guide and verify watershed-scale processes. However, managed by Blackrock
Energy, and with the direct support of scientists from five universities, and
companies such as Exelon Power, StatOil Hydro, Constellation Energy,
HydroMentia and Ecological Systems Technology, this next step of The
Chesapeake Algae Project, as the Chesapeake Consortium, seems well within
reach.
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INTRODUCTION
Algal Turf Scrubbing (ATS) is a system for utilizing algal photosynthesis to control a
wide variety of water quality parameters. Developed in the early 1980‟s at the Smithsonian
Institution, as a biomimicry of coral reef primary productivity, ATS was initially used as a tool to
manage an extensive series of living microcosm and mesocosm models of wild ecosystems. The
models ranged from coral reefs to estuaries and fresh water streams; one of the largest of the
mesocoms was a Chesapeake Bay system grading from tidal fresh waters to full coastal
salinities. Applied to closed living models, ATS functioned to control nutrients, oxygen levels,
carbonate systems, including calcification (through CO2 control) and to minimize toxic
compounds from the local human-engineered environment. ATS also allowed the development
of planktonic communities and planktonic borne reproduction in model ecosystems, as it has
little effect on the planktonic component. This early development of ATS and the models it
controlled are described by Adey and Loveland (2007). Those authors also describe how ATS
techniques, scaled up, can restore our damaged rivers, bays and lakes.
Successfully scaled-up for nutrient removal, from point-source and semi point-source
open waters, during the 1990‟s and early 21st century, ATS use ranged from aquaculture and
tertiary treatment of sewage to agricultural canal amelioration of nutrients. By 2009, eight
scaled-up ATS systems had been built and operated from coast to coast, mostly in the southern
tier of states. The northernmost unit was constructed on the lower eastern shore of Maryland.
Okeechobee, Florida, 2003 7-acre ATS system
Tilapia farm
2.5 acre Algal Turf Scrubber (ATS) Falls City, Texas
processing 10-20 Mgpd of farm stream water
Harvesting algae

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Two particularly successful early ATS operations were a 7 acre Tilapia operation in Falls
City, Texas which produced commercial quantities of fish for nine years, and a ¼ acre, 250 K
gpd tertiary sewage system in the northern Central Valley of California (Craggs et al, 1996). In
the earlier ATS floways, considerable algal primary production was achieved (yearly means
from 25-45 g(dry wgt)/m2/day), and in some cases the algal biomass was used as an animal feed
and fertilizer. In these ATS systems, the algal source was local, mostly by self-seeding from
source water, and the algal biodiversity was high, across the spectrum of algal groups.
Filamentous green algae were dominant, in terms of produced biomass and nutrient uptake.
During the last decade, the Ocala, Florida engineering firm HydroMentia built a variety of
several acre dimension ATS systems for State/municipal water quality control of small non-
point-source waters (agricultural canals, creeks), but had restricted its activities to Florida. A
multiple-site 1440 acre ATS system had been designed to remove agricultural nutrients from the
Suwannee River in northwestern Florida (Stewart, 2006), but at this time that project has not
been funded beyond engineering design phase or implemented by the state government.
The purpose of this study, funded by a generous gift from the Lewis Foundation to the
Smithsonian Institution, and described in this report, was four-fold: (1) to demonstrate non-point-
source nutrient capture capability by ATS in stream to river scale environments with mostly
lower nutrient concentrations than point-source waters; (2) to develop a system for expanding the
utilization of produced algal biomass to biofuels and other by-products; (3) to develop a process
for expanding the use of ATS capabilities to watershed scale, especially in the Chesapeake Bay
Region, currently under both a Federal Executive Order and a Federal Court Order to solve
nutrient/hypoxia problems; and (4) to demonstrate an economic basis for large-scale ATS non-
point-source treatment, with a complex of by-products, in more northerly latitudes.
To accomplish these tasks and acquire the necessary associates and supporters, numerous
ATS power point presentations were made at universities, NGO‟s and state and Federal
government agencies throughout the Chesapeake Bay Watershed and at associated universities
outside of the Watershed. Three university teams headed by Dr. Patrick Kangas at the
University of Maryland, Dr. Marty Matlock at the University of Arkansas and Dr. John Miller at
University of Western Michigan were inducted into the study; these scientific teams were
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provided Smithsonian subcontracts to demonstrate ATS capabilities, and to examine refining
processes for the ATS algal biomass. The final reports of these partners are appended.
Associations were also formed with scientific teams at the University of William and
Mary and its Virginia Institute of Marine Science (VIMS) on the York River on southern
Chesapeake Bay, the Chemistry Department at the University of Arkansas (a butanol
fermentation group headed by Prof. Jamie Hestekin), and several companies: Exelon Power,
Blackrock Energy, HydroMentia, Statoil Hydro, Ecological Systems Technology, Constellation
Energy and Interface Global. The contributions of these groups are discussed in this report along
with several process diagrams to document their participation and the results of joint work.
However, since they were not subcontract participants, funded by the Lewis Foundation gift,
reports were not requested. Blackrock Energy, having brought together a coalition of additional
universities and companies, is now serving as the lead organization in this consortium.
ATS floways were established on the Susquehanna, Great Wicomico and York Rivers in
the Chesapeake Watershed and on the Springdale tributary of the Illinois River in Arkansas.
Algal biomass from these systems and several of HydroMentia ATS units in Florida were sent to
the University of W. Michigan for the study of its chemical composition and the development of
separation processes. The extracted carbohydrates were sent to the Department of Chemical
Engineering at the University of Arkansas and were processed to butanol and hydrogen using a
semi-permeable membrane modification of the Ramey, Clostridium double-fermentation.

Muddy Run, Susquehanna River - Three ATS floways – VIMS, York River
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Muddy Run, Susquehanna River—Three ATS test floways—VIMS, York River
THE ATS ENERGY PROJECT
The Algae
Previous work with ATS, from microcosm to moderate scale had concentrated on
systems rich in either hard benthic environments (i.e. rock or branches), with abundant algal turfs
as biofilms, or aquatic flowering plants that carried periphyton on their stems. Those ATS
systems were highly dominated by filamentous green algae, particularly species of the genera
Cladophora, Spirogyra, Microspora, Ulothrix and Rhizoclonium. Diatoms and cynobacteria
were usually present, especially as epiphytes, but rarely provided significant biomass.

Typical filamentous, green dominated algal turf, growing on a basal plastic screen from a Florida
ATS. Diatoms in the canopy in the diagram at the left; will form a brown tint later in cycle at right.

This investigation concentrated on river-stream systems, where either because of their
large volume to bottom ratio and/or the predominance of sandy or muddy bottoms, planktonic
algal communities, and those diatom communities specialized to living on sand and mud bottoms
(rather than periphyton and algal turf communities), were dominant. While extensive seeding
efforts from small, rocky periphyton-dominated local streams, with abundant filamentous green
algae, were attempted, in most test floways, for most of the operational time, planktonic-sourced
diatoms came to provide the majority of the biomass. The dominant species, by biomass, of
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these ATS floways were filamentous diatoms, particularly species of the genera Melosira,
Fragilaria, Diatoma and Berkeleya. In species number, however, the unicellar diatoms, species
of Nitzschia, Gomphonema and Navicula, were prominent. Investigations of the biodiversity and
community structure of the algae on the floways of this study were carried out, and these species
and genera, along with their abundances at each site are shown in Appendix I. In general, algal
species biodiversities on these ATS systems were very high and this was especially true of the
Susquehanna floways, where over 200 species of algae were tallied.
Berkeleya rutilans
Melosira nummoloides
s
c m
f
.S ot
y a
n id
e
d la
r r
a e
s ve
.p S
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While some green algal species, filamentous and unicellular, were present on all ATS
systems of this study, they were mostly minor elements of biomass. The filamentous green alga
Spirogyra was moderately abundant on the Susquehanna floways during the summer, and the
tube-former Ulva (Enteromorpha) was ubiquitous on the floways of estuarine rivers.
Nevertheless, over time, we learned that the overwhelming biomass dominance of diatoms could
not be significantly altered, in spite of considerable effort during the first six months, particularly
at the Susquehanna site, to seed other species of periphyton. Similar efforts were undertaken for
a shorter period in Arkansas. This was not necessarily a productivity concern, as diatoms,
especially in temperate to arctic coastal waters, are the dominant producers of the plankton.
Unfortunately, due to basic physiological and structural differences between diatoms and green
algae, diatom filaments lack the tensile strength to consistently remain attached in the moderate
energy environment of ATS systems, and this is a requirement of normal ATS function. Unlike
in the earlier green algal-dominated ATS systems, significant slough, off the floway surfaces,
occurred throughout the growing cycle (typically 7 days, though reduced to 5 days in mid-
summer and increased to 14 days in mid winter).
ATS VIMS
May-July 2009
Cyanobacteria
2%
Chlorophyta
3%
Dinophyta
0%
Berkeleyarutilans (43%)
Melosiranummoloides (26%)
Licmorphasp complex (7%) Bacillariophyta
Gyrosigmasp. (5%) 95%
Nitzschiasp. complex (5%)
Fragilariopsissp. (3%)
Pseudonitzschiacf. multiseries (2%)
York River ATS: 95% of biomass is diatoms (Bacillariophyta

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