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a b s t r a c tAs the demand for biofuel products continues to rise along with the need for tertiary wastewater treatment processes to facilitate the removal of phosphorus, increasing importance is placed on the design of cultivation systems for the production of algal biomass. In addition to traditional open ponds and photobioreactors, attached algal growth systems can provide high rates of biomass production while simultaneously removing nutrients from wastewater effluent. The potential economic viability of these attached growth systems is dependent on the optimization of bed flow characteristics, inflow water quality parameters, and hydrodynamic regimes in order to maximize biomass productivity. This study monitored the productivity and nutrient removal rates of a pilot-scale attached growth system (AGS1) used to remove phosphorus from wastewater effluent at a municipal wastewater treatment plant in Fayetteville, Arkansas. These results were compared with the results from a similar system in the same watershed that was monitored in a previous study (AGS2). The performance of AGS2 was documented in a companion article in Ecological Engineering. In spite of the similarities between the systems' locations and influent characteristics, the productivities of the two systems were very different. The rates of biomass production in AGS1 and AGS2 were 4.4 ± 4.8 and 26.7 ± 16.0 g dry weight m −2 d −1 , respectively. Potential reasons for the dramatic differences in performance between the two systems are explored in this article.

Microalgae have been extensively tested for their ability to create bio-based fuels. Microalgae have also been explored as an alternative wastewater treatment solution due to their significant uptake of nitrogen and phosphorus, as well as their ability to grow in different water types. Recently, there has been significant interest in combining these two characteristics to create economic and environmentally friendly biofuel using wastewater. This study examined the growth and lipid production of the microalgae Porphyridium (P.) cruentum grown in swine wastewater (ultra-filtered and raw) as compared with control media (L−1, modified f/2) at two different salt concentrations (seawater and saltwater). The cultivation of P. cruentum in the treated swine wastewater media (seawater = 5.18 ± 2.3 mgL−1day−1, saltwater = 3.32 ± 1.93 mgL−1day−1) resulted in a statistically similar biomass productivity compared to the control medium (seawater = 2.61 ± 2.47 mgL−1day−1, saltwater = 6.53 ± 0.81 mgL−1day−1) at the corresponding salt concentration. Furthermore, no major differences between the fatty acid compositions of microalgae in the treated swine wastewater medium and the control medium were observed. For all conditions, saturated acids were present in the highest amounts (≥67%), followed by polyunsaturated (≤22%) and finally monounsaturated (≤12%). This is the first study to find that P. cruentum could be used to remediate wastewater and then be turned into fuel by using swine wastewater with a similar productivity to the microalgae grown in control media.

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