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The Water Environment Research Foundation (WERF) funded a two-year comprehensive study of nutrient removal plants designed and operated to meet very low effluent total nitrogen (TN) and total phosphorus (TP) concentrations. WERF worked with the Water Environment Federation (WEF) to solicit participation of volunteers and provide a forum for information exchange at workshops at its annual conferences. Both existing and new technologies are being adapted to meet requirements that are as low as 3.0 mg/L TN and 0.1 mg/L TP, and there is a need to define their capabilities and reliabilities in the real world situation of wastewater treatment plants. A concern over very low daily permits for ammonia caused the work to be extended to include nitrification reliability. This effort focused on maximizing what can be learned from existing technologies in order to provide a database that will inform key decision makers about proper choices for both technologies and rationale bases for statistical permit writing. To this end, managers of 22 plants, 10 achieving low effluent TP, nine achieving low effluent TN, and three achieving low effluent NH(3)-N, provided three years of operational data that were analyzed using a consistent statistical approach. Technology Performance Statistics (TPSs) were developed as three separate values representing the ideal, median, and reliably achievable performance. Technological conclusions can be drawn from the study in terms of what can be learned by comparing the different nutrient removal and nitrification processes employed at these 22 plants.

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Innovative wastewater treatment technologies are developed to respond to changing regulatory requirements, increase efficiency, and enhance sustainability or to reduce capital or operating costs. Drawing from experience of five successful new process introductions from both the inventor/developer's and adopter's viewpoints coupled with the application of marketing analysis tools (an S curve), the phases of new technology market penetration can be identified along with the influence of market drivers, marketing, patents and early adopters. The analysis is used to identify measures that have increased the capture of benefits from new technology introduction. These have included funding by the government for research and demonstrations, transparency of information, and the provision of independent technology evaluations. To reduce the barriers and speed the introduction of new technology, and thereby harvest the full benefits from it, our industry must develop mechanisms for sharing risks and any consequences of failure more broadly than just amongst the early adopters. WEF and WERF will continue to have the central role in providing reliable information networks and independent technology evaluations.

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A pilot-scale (1,000 L) continuous flow microbial electrolysis cell was constructed and tested for current generation and COD removal with winery wastewater. The reactor contained 144 electrode pairs in 24 modules. Enrichment of an exoelectrogenic biofilm required ~60 days, which is longer than typically needed for laboratory reactors. Current generation was enhanced by ensuring adequate organic volatile fatty acid content (VFA/SCOD ≥ 0.5) and by raising the wastewater temperature (31 ± 1°C). Once enriched, SCOD removal (62 ± 20%) was consistent at a hydraulic retention time of 1 day (applied voltage of 0.9 V). Current generation reached a maximum of 7.4 A/m(3) by the planned end of the test (after 100 days). Gas production reached a maximum of 0.19 ± 0.04 L/L/day, although most of the product gas was converted to methane (86 ± 6%). In order to increase hydrogen recovery in future tests, better methods will be needed to isolate hydrogen gas produced at the cathode. These results show that inoculation and enrichment procedures are critical to the initial success of larger-scale systems. Acetate amendments, warmer temperatures, and pH control during startup were found to be critical for proper enrichment of exoelectrogenic biofilms and improved reactor performance.

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Optimal secondary clarifier performance is crucial to meet treatment requirements, especially when treating peak wet weather flows (PWWFs), to prevent high effluent suspended solids (ESS) concentrations and elevated sludge blankets. A state-of-the-art computational fluid dynamic (CFD) model was successfully used as a design and diagnostic tool to optimize performance for municipal wastewater treatment plants subject to significant PWWFs. Two case studies are presented. For Case Study 1, the model was used to determine the number of secondary clarifiers that will be necessary to treat future PWWF conditions for a plant under design. For Case Study 2, the model was used to identify modifications that are currently being made to increase the clarifier capacity for handling PWWF.

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The removal of particulate material in the aeration basin of the activated sludge process is mainly attributed to bioflocculation and hydrolysis of particulate substrate. The bioflocculation process in the aeration tank of the activated sludge process occurs only under favorable conditions in the system, and several common operational parameters affect its performance. The principal objective of this research was to observe the effect of mixed liquor suspended solids, solids retention time (SRT), and extracellular polymer substances on the removal of particulate substrate by bioflocculation. A first-order particulate removal expression, based on flocculation, accurately described the removal rates for supernatant suspended solids and colloidal chemical oxygen demand. Based on the results presented in this investigation, a mixed liquor concentration of approximately 2200 mg/L, an SRT of at least 3 days, and a contact time of 30 minutes are needed for relatively complete removal of the particulate substrate in a plug-flow reactor.

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The existing theories incorporated to state-of-the-art, activated-sludge-consensus models indicate that the removal of particulate substrate from the liquid in the activated-sludge process is a two-step process: instantaneous enmeshment of particles and hydrolysis followed by oxidation. However, experimental observations indicate that the removal of particles is not instantaneous and needs a more accurate description. This removal process can actually be described as a three-step process: flocculation, hydrolysis, and oxidation. The principal objective of this research was to observe and model the kinetics of the removal of suspended particles and colloidal particles. A first-order, particulate-removal expression, based on flocculation, accurately described the removal rates for supernatant suspended solids and colloidal chemical oxygen demand (COD). The rate of reaction for removal of colloidal COD was slow and comparable to that for soluble organic matter.

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A new process, the biofilm-activated sludge innovative nitrification (BASIN) process, consisting of a moving-bed biofilm reactor (MBBR) with separate heterotrophic wasting, followed by an activated-sludge process, has been proposed to reduce the volumetric requirements of the activated-sludge process for nitrification. The basic principle is to remove chemical oxygen demand on the biofilm carriers by heterotrophic organisms and then to waste a portion of the heterotrophic biomass before it can be released into the activated-sludge reactor. By this means, the amount of heterotrophic organisms grown in the activated-sludge reactor is reduced, thereby reducing the volume of that tank needed for nitrification. For nitrification applications, the simplest method for stripping biomass was to use an in-tank technique using high shearing rates with aeration. Bench-scale testing showed sludge yields in the BASIN process were one-half of that in a control activated-sludge process and twice that of a process line with intermediate settling between the MBBR and activated-sludge stage. Critical washout solids retention times for nitrifiers were the same for all three lines, so activated-sludge volumes for the BASIN process could be reduced by 50% compared with the control. Originally conceived process concepts for the BASIN process were confirmed by the experimental work.

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