Hydrothermal carbonization (HTC) is a promising technology to convert wet wastes like septic tank wastes, or septage, to valuable platform chemical, fuels, and materials. However, the byproduct of HTC, process liquid, often contains large amount of nitrogen species (up to 2 g/L of nitrogen), phosphorus, and a variety of organic carbon containing compounds. Therefore, the HTC process liquid is not often treated at wastewater treatment plant. In this study, HTC process liquid was treated with algae as an alternative to commercial wastewater treatment. The HTC process liquid was first diluted and then used to grow Chlorella sp. over a short period of time (15 days). It was found that the algae biomass concentration increased by 644 mg/L over the course of 10 days, and which subsequently removed a majority of the nutrients in the HTC process liquid. Around 600 mg/L of algal biomass was collected in the process liquid at the end of treatment (day 15). Meanwhile, chemical oxygen demand (COD), total phosphorous, total Kheldjal nitrogen, and ammonia were reduced by 70.0, 77.7, 82.2, and 99.0% by fifteen days compared to the untreated wastewater, respectively. This study demonstrates that HTC process liquid can be treated by growing algae creating a potential replacement for expensive synthetic nutrient feeds for algal production.

No abstract

Herein, results of photoinduced pH oscillatory phenomena of microalgae in laboratory systems are presented. Microalgae are an extremely complex biomaterial in which light‐induced quantum mechanical processes induce changes in the surrounding aqueous environment (medium). A phenomenological understanding of the photoresponse by a quantitative study of pH oscillations of the medium is provided. The biochemical processes of algal metabolism and photosynthesis and the impact of light on a nitrate‐enriched medium are examined. pH variations in the external medium and the impact on future applications of microalgae are presented. External pH dominantly impacts conductivity in the solution of algal biophotovoltaic devices. This is the first dynamic study of the light‐induced pH behavior of microalgae with direct relevance to carbon capture, biophotovoltaic electricity generation, and quantum photosynthesis.