Influence of Scale on Biomass Growth and Nutrient Removal in an Algal–Bacterial Leachate Treatment System

Data collected from experiments conducted at a flask scale are regularly used as input data for life cycle assessments and techno-economic analyses for predicting the potential productivities of large-scale commercial facilities. This study measures and compares nitrogen removal and biomass growth rates in treatment systems that utilize an algae–bacteria consortium to remediate landfill leachate at three scales: small (0.25 L), medium (100 L), and large (1000 L). The medium- and large-scale vessels were run for 52 consecutive weeks as semibatch reactors under variable environmental conditions. The small-scale experiments were conducted in flasks as batch experiments under controlled environmental conditions. Kolomogov–Smirnov statistical tests, which compare the distributions of entire data sets, were used to determine if the ammonia removal, total nitrogen removal, and biomass growth rates at each scale were statistically different. Results from the Kolmogov–Smirnov comparison indicate that there is a significant difference between all rates determined in the large-scale vessels compared to those in the small-scale vessels. These results suggest that small-scale experiments may not be appropriate as input data in predictive analyses of full scale algal processes. The accumulation of nitrite and nitrate within the reactor, observed midway through the experimental process, is attributed to high relative abundances of ammonia- and nitrite-oxidizing bacteria, identified via metagenomic analysis

Longitudinal Study of Wastewater Greases and Their Potential for the Production of Biofuels

Grease-trap waste (GTW) and sewage-scum grease (SSG) are under-utilized, high-lipid waste streams that have the potential to be converted into biodiesel. This paper presents a longitudinal study of GTW and SSG samples that were obtained over a 1 year period; GTW was sampled from a storage tank at a grease-collection company, and SSG was sampled from scum-concentration buildings at three wastewater resource recovery facilities. Samples were fractionated to quantify their lipids, secondary wastewater, and solids content. Results show that the average lipid content of SSG was seasonally dependent; lipid content was 15–40% in cooler months and 3–21% in warmer months. Alternatively, GTW showed an average overall lipid content of 4% in raw GTW; however, the floating layer from settled GTW had an average lipid content of 34%. These greases could serve as feedstocks for urban low-carbon biodiesel production while reducing the volume of biosolid waste disposal