Nitrification kinetics were evaluated in bench-scale batch reactors fed with a synthetic wastewater containing approximately 1,000 mg ammonia-nitrogen (NH3-N)/L operated at 5, 10, and 20 day solids retention times (SRTs) and with dewatered biosolids supernatant (1,126 to 1,680 mg NH3-N/L) operated at a 20-day SRT. For the 5- and 10-day SRTs, complete nitrification appeared to be inhibited by the presence of un-ionized ammonia and un-ionized nitrous acid. For the 20-day SRT, near complete nitrification was observed for both substrates. Observed ammonium oxidation rates decreased with...

Class A biosolids can be produced using low-cost, low-technology biosolids treatment processes including lagoon storage, air drying, and cake storage. This project reviewed the available literature and municipal agency data about these processes. This report presents design and operating guidelines distilled from the review process. It is designed for wastewater treatment plant (WWTP) managers, operators, and engineers who wish to discern whether these processes, used alone or in combination, might be practically applied at specific plants. This report also describes the U.S. regulatory...

The presence of cationic pollutant metals in municipal wastewater effluent is a concern because stringent discharge requirements cannot always be met with conventional treatment methods. Attempts to improve metal removal are often unsuccessful because a significant fraction of the cationic metals are complexed by the synthetic chelating agent ethylenediamine tetraacetic acid (EDTA). To identify practical approaches for improving metal removal, an analytical method for measuring metal-EDTA complexes was used to survey metal speciation at a series of wastewater treatment plants. Following these...

The purpose of this research was to evaluate and compare various thermophilic anaerobic digestion processes for meeting U.S. EPA biosolids Class A pathogen standards. The project was split into three phases. Phase 1 screened three bench-scale thermophilic anaerobic process configurations at three different thermophilic temperatures based on their fecal coliform destruction efficiency. All three of the thermophilic process configurations tested were capable of achieving the Class A fecal coliform standard and were included in Phase 2. In Phase 2, bench-scale anaerobic digesters were fed...

This research attempts to evaluate nitrification treatment performance in combined carbon/nitrogen municipal wastewater reactors using traditional physical/chemical methods and modern molecular techniques. Bench scale activated sludge reactors were operated at different SRTs under varying DO levels and temperatures over a 21-month period. Real-time PCR assays were used to determine cell concentrations of total bacterial 16S rDNA, a gross measure of biomass content, the amoA gene, a measure of ammonia-oxidizing bacteria (AOB), and the Nitrospira 16S rDNA gene, a measure of nitrite-oxidizing...

Disinfection of wastewater is a necessary treatment process for protecting the public from potential exposure to pathogenic microorganisms because many wastewater effluents are discharged into water bodies that may be used for recreation or as future drinking water supplies. Two common forms of disinfection are chlorine and ultraviolet (UV) light. However, microorganisms differ in their susceptibility to UV and chlorine disinfectants. It is necessary to understand how different classes of pathogens respond to UV and chlorine disinfection processes in wastewater to better develop strategies...

The main objective of this research was to investigate the capabilities of three chemical oxidation processes as pretreatment technologies with the goal of making wastewaters containing persistent organic compounds amenable to biotreatment. The processes investigated are ozonation, ultraviolet radiation/ hydrogen peroxide (UV/H2O2) and Fenton reaction. The studies were focused on two organic compounds: Dichloro diethyl ether (DCDE) and methyl tertiary butyl ether (MTBE). Synthetic solutions, and a real groundwater and an industrial wastewater were used for experimentation. The experimental...

This report presents the results of an evaluation of technologies that may result in less biomass production in activated sludge processes. The report summarizes the results of a comprehensive literature review that was done to evaluate technologies in terms of their sludge reduction potential, ease of implementation, impacts on plant operations and effluent quality, reliability, and relative capital and operating costs. Reporting testing results supported significant biomass reduction by processes using chemical and thermal methods, higher life forms (predator processes), anaerobic instead...

Simultaneous biological nutrient removal (SBNR) is the removal of nitrogen and/or phosphorus in excess of that required for biomass synthesis in biological wastewater treatment systems where there are no defined anaerobic and/or anoxic zones. The hypothesis is that one or more of three mechanisms is responsible within individual systems: variations in the bioreactor macroenvironment created by the mixing pattern, gradients within the floc microenvironment, and/or novel microorganism activity. Understanding of the mechanisms of SBNR can be expected to lead to improved efficiency and...

There is a pressing need for developing and testing a general set of theories in order to provide a confident basis for prediction of multiple stressor effects. Confident prediction is central to confident decision making in water pollution control. Consequently, WERF commissioned this study which has as its goal to provide a study design based on good science that helps establish a general, conceptual approach to multiple stressors. The objectives of the study are to develop a flexible and scientifically defensible conceptual model of the environmental effects of multiple stressors on river...