Onsite wastewater treatment systems are commonly used to remove contaminants from septic tank effluent (STE) in Long Island, New York. However, these systems may contribute to excess phosphorus (P) loading to watersheds. Due to the STE composition fluctuation and various filter materials used in filtration-based OWTS, it is critical to understand the P attenuation, removal mechanisms, and leaching potential within the systems. The goal is to investigate the P attenuation and leaching process within the sand layer of the nitrogen removal biofilters (NRBs) when treating STE under different environmental and operational conditions. Replicate bench-scale sand columns filled with C33 sand and aged filter material (from a 5-year-old NRB) were conducted for the experiments. The attenuation and mobilization of P during (i) STE treatment and (ii) natural precipitation at various pH levels (4-6) and loadings (0.6-1.2 gallon/day/sqft) were investigated. Furthermore, the impact of filtration materials (sands, gravels, marble chips, and zeolites) on P attenuation/mobilization was investigated at high loading. Results showed that NRBs can exhibit different attenuation and leaching capacities, depending on the loading rates and characteristics of materials. 24-34% of P removal was observed in both columns when STE loading was 1.2 gallon/day/sqft. A much lower P removal (4-7%) was observed at high STE loading (12 gallon/day/sqft). P attenuated in both columns was completely leached out after 100 hours of heavy rainfall (6 cm/hour). Various STE loadings and pH impact on P attenuation and mobilization of sand matrix with various compositions (Fe, Ca, Al content) are currently under investigation.

As more stringent nutrient discharge limit will be imposed in the future, a cost-effective biological nutrient removal (BNR) technology is highly desired for equipping coastal wastewater treatment plants with nutrient removal capacity. The conventional “A2O + tertiary MBBR” process requires extensive aeration energy supply and external organic carbon addition to achieve both nitrogen removal and enhanced biological phosphorus removal (EBPR). There is a pressing need for innovation that can achieve higher nutrient removal but at lower energy demand and smaller footprints. Nitrogen removal via partial nitrification/ denitrification and anammox (PANDA) could theoretically result in a 50% reduction in aeration requirements and up to an 80% reduction in supplemental carbon compared to conventional nitrification/denitrification processes. Meanwhile, the biodegradable organic compounds in the raw wastewater or primary effluent also can be taken advantage as a free external carbon source for EBPR and denitrification. Therefore, this Water Research Foundation funded pilot work aimed to demonstrate how a conventional “A2O + tertiary MBBR” process can be easily modified to achieve EBPR, endogenous denitrification, and PANDA in one combined process to achieve effluent TIN limits of 3 mg/L. The results shows that an integration of EBPR, endogenous denitrification, and PANDA in an “A2O + tertiary MBBR” process was proven to be feasible for cost-effective nutrient removal under the system automation control. Average effluent TIN of 2.7 ± 1.8 mg/L and undetectable OP were achieved. 100% carbon and 31% oxygen were saved in the secondary treatment. 50% carbon was saved in the tertiary polishing process.

Extreme wet weather events, such as hurricanes and tropical storms, are on the rise globally due to climate change. Activated sludge systems are vulnerable to extreme wet weather, as hydraulic overloading can cause washout of biomass. During hurricane Harvey in Houston TX, excessive flooding caused significant damage to wastewater systems, including millions of gallons of active biomass washout, and numerous plants were out of service for weeks. Biofilm-based treatment technologies, such as moving bed biofilm reactors (MBBR) and membrane aerated biofilm reactors (MABR), can improve resiliency by preventing biomass washout and protecting slow growing microbes. In this study, we investigate the resiliency of these biofilm systems to extreme wet weather and examine how the microbial community changes post disturbance. We performed three simulated wet weather stressor experiments on replicate 1L bench MBBR reactors: (1) high flow and high load (representative of flooding and a first flush); (2) high flow, high load, and no DO (flooding with power outage); and (3) starvation and no DO (temporary plant shut down). We also conducted simulated high flow experiments on two pilot-scale systems: one MBBR and one MABR, fed with raw influent wastewater at a facility in Houston TX. In both pilot- and lab-scale experiments, ammonia and COD removal rates rebounded to their baseline performance in 5-10 hours post disturbance. Biofilm samples will be sequenced to assess if the microbial community shifted post disturbances. Our findings across multiple scales of experimentation show that biofilm systems are resilient to extreme wet weather events.

Un- or undertreated wastewater contains nutrients that can create water quality problems, negatively impact air quality, and release potent greenhouse gases (CH₄ and N₂O). Research has demonstrated that nitrogenous pollution causes hypoxia in estuaries globally. Wastewater treatment is, therefore, essential for protecting the environment and human health. Conventional municipal wastewater treatment technologies are highly effective and reliable, yet energy-intensive and complex, making them impractical for many small and/or rural communities.

The construction of facultative wastewater treatment ponds (“ponds”) is a promising solution to unmet wastewater treatment needs in small communities. Indeed, ponds are the most common technology used to treat wastewater in the United States and around the world. However, ponds are not designed to remove total nitrogen nor optimized to withstand cold temperatures and low dissolved oxygen (DO) concentrations associated with ice cover, and previous studies have indicated poor performance during cold seasons.

The present research focuses on understanding the factors that control ponds’ performance such that they can be used for sustainable nitrogen removal. We are examining pond system performance and microbiological community characteristics with an emphasis on conditions of low oxygen and/or low temperature. Laboratory scale nitrification experiments are coupled with a field study of the fate and transport of nitrogen in six full-scale ponds in Minnesota over four seasons. We have found that nitrification proceeds slowly under low DO concentrations, suggesting that the presence of even low quantities of DO under winter ice cover may stimulate nitrification and thereby total nitrogen removal via coupled nitrification-denitrification.

Biogas generated from anaerobic digestion (AD) with feeding organic waste has gained much attention. But subsequent treatments are needed to upgrade the biogas to renewable natural gas (RNG), an alternative option for fuel and heat. This study investigated a hybrid biogas upgrading approach through H₂ addition with membrane employed. Synthetic wastewater was used to mimic brewery wastewater as a substrate. The reactor was designed vertically with three different function zones: AD zone, bioconversion zone, and gas-liquid separation zone. Continuous H₂ addition into the reactor and inner circulation effectively increased the CH₄ content in the biogas. The addition of 2, 4, and 6 equivalents of H₂ relative to CO₂ was investigated. Optimal upgrading situation achieved when methane content was increased to 90%. Biofilm was formed on the membrane in the bioconversion zone. Enriched hydrogenotrophic methanogen was found in the biofilm. Hybrid biogas upgrading was achieved in a single reactor without additional units, which could be a promising reactor configuration to achieve high-performance biogas upgrading.

Keywords: hybrid biogas upgrading; CO₂ bioconversion; H₂ transfer; gas permeable membrane.