Biological Nutrient Removal

Excessive nutrients loading is still one of the main causes for impairment of coastal and freshwater ecosystems. Excess nitrogen (N) and phosphorus (P) can lead to eutrophication and cause water quality and ecosystems integrity deterioration. Nutrients loading come from both point and non-point sources. As part of the point-source control strategy, many public agencies are forced to install and upgrade their wastewater treatment facilities to meet the increasingly stringent effluent N and P limits. The current challenges the environmental engineers/scientists are facing for wastewater nutrient removal include: limits of technologies for achieving extremely low effluent nutrient limits, more environmental-friendly yet efficient and stable treatment processes that can reliably meet compliances, high capacity and small-foortprint processes and energy-efficient or energy-recovering processes. Following are some of the examples of how we are working towards addressing some of these challenges.

Advanced nutrient removal by IFAS-EBPR-MBR process

Biological nutrient removal (BNR) process is still the most commonly applied technology for removing nitrogen and phosphorus from municipal wastewater.In order to achieve low effluent total nitrogen the following conditions are required: 1). Long SRT , 5-25 days depending on temperature and loads, is required to achieve complete nitrification to produce effluent NH4-N <0.5 mg/L. 2). Efficient denitrification, either via pre-denitrification and/or post-denitrification, is needed to produce low effluent total oxidized nitrogen (TON).

We are studying the simultaneous removal of N and P using an Integrated Fixed Film Activated slusge system. We also aim to evaluate the microbial population in a lab-scale IFAS-BNR plant.

Laboratory scale IFAS-MBR

Evaluation of alternative carbon sources for Denitrification

Requirement of external carbon sources for denitrification and for enhancing biological phosphorus removal is becoming more common for POTWs that are facing increasingly stringent effluent nutrient limits. External carbon addition to pre-denitrification anoxic zones can help increase the denitrification rate and nitrogen removal efficiency, addition to post-denitrification zone is required for effluent total nitrogen of less than 6 mg/L, and addition to anaerobic zone for enhanced biological phosphorus removal is shown to improve the system performance and stability. Commonly used external carbon sources include methanol, ethanol, sugar and sludge digestion supernatant. Other alternative carbon sources that have been proposed recently include molasses, glycerol, corn starch and others. MicroC™ is a proprietary wastewater treatment chemical developed by Environmental Operating Solutions, Inc. and designed specifically for use as an electron donor/carbon source for biological denitrification of wastewater.

Three sequencing batch reactors were established to acclimatize the biomass to three different carbon sources, MicroC™, methanol and acetate. The SBRs has operated for 1 and half year and the acclimated sludge is used for batch testing to determine kinetics.

SBRs Pilot

Water quality evaluation and monitoring

The goal of sustainable water resources development and management is to meet water needs reliably and equitable for current and future generations by designing integrated and adaptable water management and treatment systems to implement water conservation, optimize water-use efficiency, increase water recycle and reuse and make continuous efforts toward preservation and restoration of natural ecosystems. Water reclamation is the treatment or processing of wastewater to the extent that is becomes reusable with definable treatment reliability and meeting water quality criteria. The chemical and microbial constituents of concern for water quality expands over the conventional parameters and they include suspended and colloidal particulates, organic matter, dissolved organic matter, nitrogen and phosphorus, trace contaminants, bacteria, protozoa and viruses. Within the trace contaminants, special attention has been brought on the constituents that has extremely low concentrations but with significant potential health impact such as endocrine disruptors, pharmaceutical compounds and personal care products. Monitoring of unconventional and emerging pollutants is still a challenge due to the large and increasing number of potential contaminants being identified with advancement of analytical methods and uncertainty associated with their toxic effects on aquatic life and human.

Toxicogenomics

Living cell respond to environmental stress changing some metabolic activity. This results in the activation of specific genes. If the expression level of these genes is monitored, the gene expression could be used to identify the toxicompounds.

The overall goal is to establish a knowledge database of gene expression profiling (finger print) of a large number of environment relevant class of pollutants, allowing for future classification or potentially identification of toxic contaminants in water and wastewater samples.

 

Bioavailability of wastewater-derived refractory dissolved organic nitrogen (rDON) to eutrofying biota

Dissolved organic nitrogen (DON), which contributes an increasingly larger percentage (up to 85%) to the total N content in highly treated wastewater effluents (relative to 20% of total N in traditional wastewater effluents), is now drawing significant attention from both regulatory agencies and wastewater utilities. For utilities, the concern arises from the substantial capital cost that is required to implement more advanced treatment technologies beyond the current limit of technology (LOT) in order to remove the DON. On the regulatory side, current watershed protection plans (e.g. TMDLs) use total nitrogen for setting limits without considering the possibility that DON and inorganic nitrogen may differ in their bioavailability and therefore their potential to cause cultural eutrophication. This has motivated the regulated community and utilities to assess whether the DON in wastewater effluent is actually labile and therefore harmful to the receiving waters.

The overall objective of this study is to investigate the bioavailability of wwDON to freshwater phytoplankton and assess and quantify the contribution, if any, of wwDON to primary production and eutrophication.Bioavailability of wwDON can be assessed via algal growth bioassay, and the lability varies among different phytoplankton species, particularly the N2-fixing algae versus non-N2-fixing algae.

Microbial Population dynamics in biological nutrient removal processes

Our focus is to applied modern leading edge molecular technologies to investigate the key funtional groups involved in N and P removal , particularly AOB, NOB, PAO, GAOs.

Fish photograph of a IFAS plant sludge sample

Bioremediation

Perchlorate Reduction

Perchlorate, a predominantly man-made toxic anion, has been identified in recent years as a significant water contaminant throughout the United States.Our research focuses on determine if perchlorate reducing bacteria are present in wastewater treatment plant, and find who they are!

To check out the poster on our research activities click here!