Algal turf scrubber (ATS) floways on the Great Wicomico River, Chesapeake Bay: productivity, algal community structure, substrate and chemistry¹

Abstract

Two Algal Turf Scrubber (ATS) units were deployed on the Great Wicomico River (GWR) for 22 months to examine the role of substrate in increasing algal productivity and nutrient removal. The yearly mean productivity of flat ATS screens was 15.4 g · m(-2) · d(-1) . This was elevated to 39.6 g · m(-2) · d(-1) with a three-dimensional (3-D) screen, and to 47.7 g · m(-2) · d(-1) by avoiding high summer harvest temperatures. These methods enhanced nutrient removal (N, P) in algal biomass by 3.5 times. Eighty-six algal taxa (Ochrophyta [diatoms], Chlorophyta [green algae], and Cyan-obacteria [blue-green algae]) self-seeded from the GWR and demonstrated yearly cycling. Silica (SiO2 ) content of the algal biomass ranged from 30% to 50% of total biomass; phosphorus, nitrogen, and carbon content of the total algal biomass ranged from 0.15% to 0.21%, 2.13% to 2.89%, and 20.0% to 25.7%, respectively. Carbohydrate content (at 10%-25% of AFDM) was dominated by glucose. Lipids (fatty acid methyl ester; FAMEs) ranged widely from 0.5% to 9% AFDM, with Omega-3 fatty acids a consistent component. Mathematical modeling of algal produ-ctivity as a function of temperature, light, and substrate showed a proportionality of 4:3:3, resp-ectively. Under landscape ATS operation, substrate manipulation provides a considerable opportunity to increase ATS productivity, water quality amelioration, and biomass coproduction for fertilizers, fermentation energy, and omega-3 products. Based on the 3-D prod-uctivity and algal chemical composition demonstrated, ATS systems used for nonpoint source water treat-ment can produce ethanol (butanol) at 5.8× per unit area of corn, and biodiesel at 12.0× per unit area of soy beans (agricultural production US).

Advanced nutrient removal from surface water by a consortium of attached microalgae and bacteria: A review

“…This unique performance makes algal-bacterial biofilm based photobioreactors a more attractive platform for advanced nutrient removal from surface water than other commonly used technologies including constructed wetlands and ecological floating beds (Table 4). For instance, Adey et al (2013) reported that the TN and TP of the Great Wicomico River remained at 0.3-0.6 and 0.01-0.03 mg L À1 , respectively, during ATS operation. Similarly, Boelee et al (2011) reported TN and TP of 0.1 and 0.05 mg L À1 , respectively, in the treated effluent of municipal wastewater by microalgal biofilms.…”

“…Understanding of the complex interactions between attached microalgae and bacteria is pointing out how cooperative interactions allow for functionally stable consortium (Borowitzka, 2016;Ramanan et al, 2016). Besides, the increasing implementation of photobioreactors using attached microalgaebacteria consortium, such as Algal Turf Scrubbers (ATS) (Adey et al, 2013), tank photobioreactors (Su et al, 2011) and tubular biofilm photobioreactor (De Godos et al, 2009), are delivering valuable information about nutrient removal at low concentrations. Recent progress in genomic techniques also allows a better identification of functional microorganisms and the genes involved in nutrient removal (Lindemann et al, 2016;Liu et al, 2016b).…”

“…Microalgae increase the pH and DO level of water by capturing CO 2 and releasing O 2 through photosynthesis (Adey et al, 2013;Liu et al, 2016a), while the uptake of inorganic nutrient and metals, mineralization of organic nitrogen, anaerobic ammonia oxidation, nitrification, denitrification and degradation of organic matter by microbial organisms reduce the nutrient and organic matter concentrations of surface water, thereby improving water quality (Boelee et al, 2011;Cao, 2016;Su et al, 2016). Furthermore, the Fig.…”

“…ATS has been successfully applied to the treatment of river water, agricultural, aquaculture and domestic wastewater at commercial scale. However, the fact that algal-bacterial biomass must be installed at the top layer of surface water limits ATS application to the insitu remediation of deep water (Craggs et al, 1996;Mulbry et al, 2010;Adey et al, 2013).…”

“…Natural substrate colonization and artificial inoculation are the two main mechanisms to obtain attached microalgae-bacteria consortium, with many substrate materials being tested for algalbacterial biofilm formation (Table 5) (Yu and Mohn, 2002;Adey et al, 2013;Kesaano and Sims, 2014;Gross et al, 2015b;Liu et al, 2016a). Natural colonization occurs spontaneously whenever a solid substrate is under proper climate and nutrient conditions in surface water (Mulbry et al, 2008;Liu et al, 2016b;Su et al, 2016).…”