Final Report: Sustainable Biological Phosphorous Removal: A New Theory to Meet Increasingly Stringent Effluent Discharge RequirementsEPA Grant Number: SU833554
Title: Sustainable Biological Phosphorous Removal: A New Theory to Meet Increasingly Stringent Effluent Discharge Requirements
Investigators: Loge, Frank , Barkouki, Tammer H. , Anderson, Dane , Anderson, Jeffery , Moniz, Ryan
Institution: University of California - Davis
EPA Project Officer: Page, Angela
Project Period: August 31, 2007 through July 31, 2008
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2007) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Water , P3 Awards , Sustainability
A great challenge to sustainability is developing a method of phosphorous removal in wastewater to achieve low effluent concentrations without adding hazardous chemicals. In our Phase I study, we proposed to make wastewater treatment systems more sustainable by developing a more effective way of biologically removing phosphorous. Through our research we understood the mechanisms of enhanced biological phosphorus removal (EBPR) and we developed a new process that reliably and stably accounts for near complete removal of phosphorous from wastewater. An alternative to current EBPR theory, we proposed the study of a new theory that more comprehensively integrates the complex microbial metabolisms occurring within a real wastewater environment. We propose that the removal of phosphorus is governed by the stress response, or stringent response, of microbial consortia subjected to unbalanced growth conditions within wastewater treatment. A biological process designed to optimize the microbial stringent response can meet strict discharge limits (0.01 to 0.02 mg/L) set forth by the US EPA. As EBPR is currently the most environmentally benign method of phosphorous removal, making this process more reliable and stable will diminish dependence on chemical processes and will make a significant contribution towards the overall sustainability of water treatment processes.
Our research objective was to develop design and operation criteria for full scale facilities based on this new theory. Specifically, we wanted to determine how the microbial stress response is affected by nutrient feed conditions and transient availability of oxygen. We hoped to use the data collected in the laboratory to estimate appropriate rate coefficients, and then use these coefficients in mathematical models to develop a conceptual design of a full-scale system.
Research prior and during Phase I work led to the conclusion that phosphorus removal in wastewater treatment is driven by metabolic processes centered on microbial stringent response. It has been observed that the microbial stringent response depends on nutrient feed stock and the environmental zone (anaerobic or aerobic). The laboratory work was not able to produce clearly defined rate coefficients, MCRTs and HRTs for larger-scale operational design. The primary result of our Phase I research is the integrated system in which we run the bioreactor. We have found that the microbes in the bioreactor must be kept in very specific conditions in order for them to grow and remove phosphorus. These conditions include an aerobic and anaerobic phase as well as once a day feeding and once a day removal of treated water.
The lab data was collected in order to allow us to (a) assess the role of the microbial stringent response in biological phosphorous removal, and (b) obtain a set of rate coefficients that will allow us to design a large-scale pilot system. As part of the full-scale design, a mathematical spreadsheet was developed that simultaneously solves the mass balance equations for the different constituents in a wastewater treatment process. This mathematical spreadsheet method can be easily manipulated to provide operational criteria for both continuous flow stirred tank reactors (CFSTRs) and plug flow reactors. The mass balance equations are evaluated around each tank (activated sludge reactors, and clarifiers) for substrate, viable and dead cells. Oxygen and phosphorous demands are then calculated. Results of this work in Phase II will help design and construction of a pilot-scale plant.
The laboratory work for this project was well designed and prepared, but faced many unseen challenges. Due to these challenges, we were unable to collect any MCTR, HRT, and rate coefficient data in time for this report. Despite the lack of concrete data, we have learned much about the process of phosphorus removal and microbial stringent response. We are confident that given more time we would produce tangible results in the form of rate coefficients for phosphorus removal. The laboratory work itself was a learning experience for the students working on the project. The planning and organizational aspects of the laboratory work showed persistence in the students when faced with numerous obstacles. A bioreactor is a fragile ecosystem with many different species of microbes. If poorly or inconsistently maintained, the ecosystem breaks down within the reactor.
We have identified this system of phosphorus removal as a viable and sustainable alternative to traditional methods which rely heavily on non-sustainable chemical additions. In using a mathematical program for the design of a pilot-scale treatment plant, we expect success in ultimately integrating our new system into full-scale facilities.
Proposed Phase II Objectives and Strategies:
The challenge of Phase II is constructing a large-scale pilot system to sustainably remove phosphorus from wastewater at a full-scale wastewater treatment plant. With the design and operational criteria that were developed in Phase I, the pilot-scale system will be specifically designed to achieve very low effluent concentrations of phosphorus while still meeting permitted effluent concentrations of carbon. In efforts to maximize the efficiency of the pilot-scale system, we will modify our design criteria using data collected from the pilot system. Because biological phosphorus removal has the potential to be both progressive and sustainable, particular attention will be paid to investigating methods of utilizing phosphorus extracted from wastewater for soil fertilization practices. Additionally, we will complete a life-cycle analysis of our new biological treatment process. Once complete, we hope to implement our process in full-scale facilities and work to gradually replace the practice of chemical phosphorus removal in wastewater treatment.