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Abstract: The lack of readily available sources of potable water is major problem in many parts of the world. This project engaged high school (HS) students in authentic and meaningful science and engineering activities to teach them about the lack and poor quality of potable water in many regions and how they can be addressed through the use of point of use (POU) treatments, such as biosand filters (BSFs). The HS students’ activities paralleled those of USF students, including research question development and BSF design, construction, operation, and monitoring. An ethnographic approach was utilized by incorporating participant observation, collection and review of artifacts, and interviews. It was found that the project’s focus on the need to provide potable water in the developing world provided authenticity and meaningfulness to the HS students, which encouraged their participation in activities and the learning of science and engineering practices. The HS students reported an awareness of the differences between this project and their regular science classes. The project had a positive impact on their perceptions of themselves as scientists and their interest in STEM careers. The HS students’ results were useful to the university-based research. In addition, the USF students gained teaching experience while investigating research questions in a low-stakes environment. 

Hundreds of millions of people worldwide have limited access to safe, clean drinking water. Although for most Americans this problem may seem very far removed from their experience, there are many resources available on the internet that can bring the reality of water scarcity into the classroom. We have found this to be a problem that resonates with many students when they become aware of how it affects people their own age. Experimenting with BSFs is a way for students to participate in solving the problem of water scarcity, poor water quality, and inadequate sanitation that have negatively impacted the health and livelihoods for families around the world. In addition, it can provide students with a voice and empower their capacity in STEM in two ways, first by their authentic engagement in the SEPs, and second, by investigating ways to enhance the efficacy and operation of BSFs that could help those in need of an inexpensive way to purify their water 

A hybrid ion-exchange and algal photosynthesis (HAPIX) process was used for treatment of side stream centrate from an anaerobic digester treating waste activated sludge. Although the high NH4+-N concentration of the centrate (~1180 mg/L) inhibited algal growth in unamended controls, addition of zeolite reduced the ammonia toxicity due to its ion exchange capacity. Na+ was the major cation exchanged with NH4+. Growth of algae further reduced the NH4+-N concentrations. Different zeolite dosages (60, 150, and 250 g/L) resulted in different concentrations of NH4+-N in solution. Algae grown in lower zeolite dosage (60 g/L) had high protein contents. A mathematical model that combined ion-exchange and algal photosynthesis processes predicted the aqueous NH4+-N concentration well. The HAPIX process is feasible for treatment of high NH4+-N strength side stream wastewaters while regulating intracellular algal biomass contents by adjusting zeolite dosages. 

A hybrid ion-exchange and algae photosynthesis (HAPIX) process was used for treatment of side stream centrate from an anaerobic digester treating waste activated sludge. Although the high NH4+ -N concentration of the centrate (~1180 mg/L) inhibited the algae growth in unamended controls, addition of 150 g/L of zeolite reduced the ammonia toxicity due to its ion exchange capacity. NH4+-N was reduced from 1,180 mg/L to 107 mg/L within 24 hours by ion exchange. Na+ was the major cation exchanged with NH4+. The addition of algae further reduced the NH4+-N concentration to 10.5 mg/L after 8 days of operation. Zeolite that was saturated with NH4+ can be bioregenerated by the algae growth so that the zeolite can adsorb more NH4+ in the wastewater. The mathematical model that combined ion-exchange and algal photosynthesis processes predicted the aqueous NH4 + -N concentration well. The HAPIX process is feasible to treat high NH4+-N side stream wastewater. 

Algae-based wastewater treatment systems have the potential to reduce the energy cost of wastewater treatment processes by utilizing solar energy for biomass growth and nutrient removal. NH4+-N concentrations as high as 200- 300 mg/L are known to inhibit algae growth. Many research studies on the treatment of centrate after anaerobic digestion have been published recently. However, in these studies the centrate was diluted for the growth of algae due to the high NH4+-N concentrations, which are toxic to algae. Alternative solutions are necessary to treat high NH4+-N strength wastewater without addition of freshwater. Zeolites are natural hydrated aluminosilicate minerals that have been used to reduce ammonium inhibition on microorganisms due to their high affinity for ammonium ions. It is possible to use the ion-exchange (IX) capacity of zeolite to reduce the toxicity of ammonia to algae. Importantly, the zeolite, which becomes saturated with ammonium, can be reused as a slow release fertilizer. The objectives of this research were to evaluate the impact of zeolite dosage on the nutrient removal efficiency for high strength wastewater and develop mathematical models to predict the performance of hybrid IX and algae growth systems with varying doses of zeolite.