Comparison of Scale in a Photosynthetic Reactor System for Algal Remediation of Wastewater

Bioremediation of Raw Landfill Leachate Using Galdieria sulphuraria: An Algal-Based System for Landfill Leachate Treatment

This study aims to evaluate the potential of using a thermophilic acidophilic red alga, Galdieria sulphuraria for effective on-site treatment of municipal landfill leachate (LL). This study focused on evaluating the effects of LL dilution, nitrogen loading, and initial algal biomass density on the overall treatment efficiency, and evaluated the long-term performance of the system using 5-day growth cycles. This study confirmed that optimal conditions for G. sulphuraria biomass production are 20% strength LL, a lower initial biomass concentration of 0.25 g L−1, and the addition of N at twice the level of initial media. Furthermore, the results indicated G. sulphuraria’s ability to grow in elevated NH4-N concentration (>950 mg L−1) and provide nitrogen removal rates of up to 40 mg L−1 d−1. In addition, the long-term running experiment showed that the proposed algal-based system could be applied in semi-continuous mode to achieve bioremediation. Overall, the results obtained from this study can be used to develop the necessary process parameters to implement large-scale algal-based systems for landfill leachate treatment.

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.