Economic Considerations on Nutrient Utilization in Wastewater Management

Abstract

There is wide consensus that Spirulina can serve as a tool for wastewater management and simultaneously provide feedstock for biorefining. However, the economic aspects associated with its use remain a significant challenge. Spirulina cultivated in wastewater decreased the concentrations of both ammonia and nitrate and also served as a biodiesel source. The oil obtained in the feedstock was subjected to transesterification and turned into biodiesel. The biodiesel was subsequently analyzed in a test motor (water-cooled, four-stroke, single-cylinder compression ignition with injection). The tests were conducted at a constant 1500 rpm, and the output power was 3.7 kW. Mixtures of diesel and biodiesel were also enriched with carbon nanotubes (CNTs). The amount of CNTs added to the diesel was 30 mg L−1. The algae and de-oiled biomass were characterized using XRD analysis, and an ultrasonicator was used to mix the CNTs with diesel and spirulina blends. A series of tests were conducted at different load conditions (25%, 50%, 75%, and 100%) for all fuel blends. Test results were compared with a neat diesel engine with a CR of 17.5:1. Among the fuel blends, the B25 reported improved brake thermal efficiency and reduced emissions. The outcomes are a reduction in thermal efficiency of 0.98% and exhaust gas temperature of 1.7%. The addition of Spirulina biodiesel blends had a positive impact on the reduction of greenhouse gas emissions, including reductions of 16.3%, 3.6%, 6.8%, and 12.35% of CO, NOx, and smoke, respectively. The specific fuel consumption and CO2 emissions were reduced by 5.2% and 2.8%, respectively, for B25 fuel blends compared to plain diesel and B50. Concerning cost competitiveness, vigorous research on microalgae for the production of biodiesel can cut production costs in the future.

Application of Internal Carbon Source from Sewage Sludge: A Vital Measure to Improve Nitrogen Removal Efficiency of Low C/N Wastewater

“…Thus, it is essential to remove nitrogen compounds before wastewater is discharged to rivers or lakes. Currently, the most efficient and common approach to this endeavor is biological nitrogen removal technology, on account of high treatment efficiency and relatively low cost [5,6]. Generally, the biological nitrogen removal process can be divided into two parts, nitrification, and denitrification, based on the bacteria involved [7,8].…”

Constructing an Adoption Model of Proactive Environmental Strategy: A Novel Quantitative Method of the Multi-Level Growth Curve Model

“…It is important to explore the driving factors of the proactive environmental strategy (PES) because it can achieve pollution reduction and sustainable production of agricultural products. Indeed, although previous studies have used environmental engineering technology to recycle and reuse the elements in agricultural fertilizers to reduce environmental pollution [8,9], this may still be less effective than the direct use of a PES in agricultural production.…”

MgO-Based Board Materials for Dry Construction Are a Tool for More Sustainable Constructions—Literature Study and Thermal Analysis of Different Wall Compositions

“…The technological progress of society has far-reaching consequences, and the globalization process significantly affects the state of the environment [1][2][3][4]. The construction industry contributes enormously to environmental degradation [5,6].…”