- NSF-PAR ID:
- 10112111
- Date Published:
- Journal Name:
- 27th Caribbean Water and Wastewater Conference & Exhibition Proceedings
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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A Novel Community Engaged System Thinking Approach to Controlling Nutrient Pollution in the Belize Cayes Nutrient pollution (anthropogenic discharge of nitrogen and phosphate) is a major concern in many parts of the world. Excess nutrient discharge into nutrient limited waters can cause toxic algal blooms that lead to hypoxic zones, fish die-offs, and overgrowth on reefs. This can lead to coral reefs being more vulnerable to global warming and ocean acidification. For coastal communities that depend of fishing and tourism for their livelihood, and for reefs to protect coastlines, these effects can be devastating. A major source of nutrient input into the aquatic environment is poorly treated wastewater from Onsite Wastewater Treatment Systems (OWTS). When properly sited, built, and maintained conventional OWTS are great for removing fats, grease, biological oxygen demand (BOD), and total suspended solids (TSS), but they are rarely designed for nutrient removal and commonly have high nutrient levels in their effluent. This study investigates the factors that influence the performance of OWTS, the Caribbean region’s most common type of treatment technology, in the Belizean Cayes where salt water flushing is common. Using mass-balance-based models for existing and proposed OWTS to predict the system’s performance under various conditions, along with OWTS’ owner, maintainer, and user input, a novel community engaged system thinking approach to controlling nutrient pollution will be developed. Key model performance metrics are concentrations of nitrogen species, BOD, and TSS in the effluent. To demonstrate the model’s utility, a sensitivity analysis was performed for case studies in Belize, estimating the impact on nutrient removal efficiency when changes are made to variables such as number of daily users, idle periods, tank number and volume, oxygen concentration and recirculation. For the systems considered here, strategies such as aeration, increased biodigester tank size, addition of aerobic and anoxic biodigesters, recirculation, addition of a carbon source, ion exchange media is predicted to decrease the effluent nitrogen concentration, and integration of vegetation for nutrient uptake both on land and in the nearshore environment. In a previous case, the addition of an aerator was predicted to decrease the effluent ammonium concentration by 13%, whereas increasing the biodigester tank size would only decrease the effluent ammonium concentration by ~7%. Model results are shared with system manufacturers and operators to prioritize possible modifications, thereby optimizing the use of finite resources, namely time and money, for costly trial-and-error improvement efforts.more » « less
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Abstract Pharmaceuticals and personal care products (PPCPs) are contaminants of emerging concern that derive primarily in the water environment from combined sewer overflows and discharges from industrial and municipal wastewater treatment facilities (WWTFs). Due to incomplete removal during wastewater treatment, PPCP impacts to aquatic ecosystems are a major concern. The Great Bay Estuary (New Hampshire, USA) is an important ecological, commercial, and recreational resource where upstream WWTFs have recently been under pressure to reduce nitrogen loading to the estuary and consequently upgrade treatment systems. Therefore, we investigated the distribution and abundance of 18 PPCPs and three flame retardants within the Great Bay Estuary and WWTFs discharging to the estuary to examine how WWTF type influenced PPCP removal. All 21 analytes were frequently detected at μg/L to ng/L concentrations in influent and effluent and ng/kg in sludge. WWTFs with enhanced nutrient removal and longer solids retention times correlated to higher PPCP removal, indicating facility upgrades may have benefits related to PPCP removal. Understanding PPCP fate during treatment and in downstream waters informs our ability to assess the environmental and ecological impacts of PPCPs on estuarine resources and develop mitigation strategies to better protect marine ecosystems from emerging contaminant exposure.
Practitioner Points PPCP removal positively correlated with solids retention time and varied by treatment facility and compound.
Upgrade of WWTFs for biological nitrogen removal may also increase PPCP removal.
Surface water fluoxetine concentrations may present an ecological risk to the Great Bay Estuary.
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com pleteamm oniaox idizer (comammox)Nitrospira Nitrosa was identified as the main nitrifier in the system. Bioaugmentation was shown to be successful as nitrifiers returned from BNR were able to increase the nitrifying activity of the high carbon removal rate system. There was a positive correlation between returned sludge from the BNR stage and the specific total kjeldahl nitrogen (TKN) removal rate in A stage. The bioaugmentation process resulted in a remarkable threefold increase in the specific TKN removal rate within the A stage. Result suggested that recycling of WAS is a simple technique to bio‐augment a low SRT system with nitrifiers and add ammonia oxidation to a previously non‐nitrifying stage. The results from this case study hold the potential for applicable implications for other WWTPs that have a similar operational scheme to Blue Plains, allowing them to reuse WAS from the B stage, previously considered waste, to enhance nitrification and thus improving overall nitrogen removal performance.Practitioner Points Comammox identifying as main nitrifier in the B stage.
Comammox enriched sludge from B stage successfully bio‐augmented the East side of A stage up to threefold.
Bioaugmentation of comammox in the West side of A stage was potentially inhibited by the gravity thickened overflow.
Sludge returned from B stage to A stage can improve nitrification with a very minor retrofits and short startup times.
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