NPR recently ran a story on people consuming fish from the Passaic River in New Jersey (I put the link below).
The problem with consuming these fish on a regular basis is that the river sediments contain high levels of industrial waste from an era where environmental regulations were limited or did not exist. The area of concern is the final 17 miles of river near Newark, NJ. This section has a variety of contaminated sludge hot spots where contaminants range from dioxin, PCBs, mercury, other heavy metals, and a variety of pesticides. Early cleanup efforts removed the most contaminated soils and sludge located near the former industrial sites where the pollutants emerged. Now their is debate on how to achieve final cleanup of the river.
From the NPR report, I gather that the current fish exchange program where contaminated fish are exchanged for tilapia iis a waste of funds. So it is clear a long term cleanup project is needed. However, the current proposed project to remove over 4 million cubic yards of sludge for off-site disposal and/or off-site incineration seems to be a bit overkill as the risk of transporting all the sludge and disturbance to buried sediments may pose a greater risk of exposure than necessary.
In previous cleanup projects, the best solution is to find the hot spots of the most dangerous and recalcitrant pollutants. For example we would immediately dredge sediments with the highest mercury, PCBs, or Dioxin. This would go for off-site incineration/landfill. The sludges with lowest levels of recalcitrant contamination may be best left in place for biormediation or natural attenuation.
Dr. John Pardue, an environmental engineering researcher at Louisiana State University, has suggested the use of an in-situ bioremediation technique that injects high concentrations of active degrading microbes and needed nutrients into the sediments suited for bioremediation. In my experience, they could also add some additional localized mixing to increase biodegradation rates without exposing residents to high levels of pollutants. If the amount of excavated sediment can be reduced by 30 - 50%, not only money will be saved, but potential exposure during removal and transport will be reduced, and finally land fill space and associated risks will be reduced.
Biological removal of phosphorus is done by a group of microbes that accumulate phosphate inside the cells at up to 30% by weight. This compares to other bacteria that accumulate phosphate at an average of 1 - 2% by weight.
In biological nutrient removal, we engineer systems to favor the growth of aggressive phosphate accumulating organisms. This is done by having an anaerobic zone (negative redox potential without nitrate/nitrite present) along with soluble organics (preferentially organic acids). This is why the BNR system usually has influent entering into the anaerobic chamber. In this step the Phosphate Accumulating Organisms (PAO) - release phosphate yielding the energy need to accumulate soluble organics (a food source). This is why in the anaerobic reaction step, we see an increase in soluble phosphate.
After reacting with influent organics in the anaerobic zone, the PAO organisms enter the aerobic portion of the treatment system. With abundant oxygen, the organisms "digest" the accumulated organics and use some of the energy to uptake soluble phosphorus. As the organisms are exposed to repeated cycles of anaerobic/aerobic conditions - the system should favor the growth of organisms with the ability to uptake carbon (food) in the anaerobic zone. With excess phosphate in the water - a number of the promoted organisms should be PAO bacteria.
What problems can happen? If the anaerobic/aerobic zones do not sufficient residence time the process can lose stablity. Additionally, some influent may not have a good oraganic makeup to encourage the PAO development. Also, if nitrate is present in the recycle to the anaerobic chamber - PAO bacteria will not have as big advantage.
In all - phosphate removal relies on providing conditions that favor the PAO bacteria. This requires understanding their unique ecology and making sure that you are not overlooking one of the key factors promoting their growth.
Waste treatment systems often have odor complaints at lift-stations, headworks, and primary clarifiers as influent wastes with high levels of sulfides, hydrogen sulfide, mercaptans, and volatile organic compounds experience mixing which increases atmospheric volatiliazation. Frequent control options include covering the area with a physical barrier and spraying perfumes or masking agents. A newer option for the most offensive areas is the construction of a biological filter that is designed to culture microbes that remove the most offensive compounds from the atmosphere.
In this post, I am going to discuss the microbiology of atmospheric treatment and how these towers all work on a biochemical level. In general, the towers are all based on a biofilm growing on a support media. The media allows for biofilm development with the biofilm receiving energy from sulfides and volatile organics. The other nutrients, pH controls, oxygen and moisture are maintained via water recirculation over the media.
Biologically the towers usually support two distinct communities of microbes.
First, are the chemo-autotrophic organisms that oxidize reduced sulfur species for energy and use carbon dioxide as their carbon source. This group is often referred to as Thiobacillus, Starkeya, or Thiosphaera sp. This group of microbes can oxidize reduced sulfur into elemental and sulfate forms. This process releases acids which are often associated with concrete degradation. In the biotower, we manage the pH to keep it in the ideal range for sulfide oxidizing microbes usually a pH of 3.5 – 6.5.
A second group of microbes that can metabolize short-chain volatile fatty acids (acetic, butyric, propionic) and mercaptans are also present. This group of microbes are often discussed as we often view odors as coming from H2S. However, in many systems the organic acids are a greater problem. In this case the biotower will favor the heterotrophic organisms which required a slightly higher ideal pH. Usually these microbes thrive from 6.0 – 8.5.
Additionally, several organisms are known to both degrade short chain volatile organics and oxidize sulfides. In some biofilters, it is beneficial to add concentrates of these cultures to rapidly colonize the media with a biofilm capable of addressing both the sulfide and organic acids. This ability to add cultures is obviously beneficial in reducing startup time, but it is also an effective option in building a biofilm in filters with high seasonal loading variation or where the biofilm integrity was compromised by mechanical failure.
Because of slow growth rates and requirements for a relatively narrow pH & dissolved oxygen range, nitrifiers are some of the most delicate microbes in a wastewater system. Making up only a small percentage of the overall biomass (measured as MLVSS), a loss in viable nitrifiers can cause long run problems in maintaining needed ammonia removal.
I have talked many times about how D.O., alkalinity, pH, and temperature can effect nitrification. This time, I want to mention the most common toxic compounds that even with low concentrations or brief exposure can inhibit ammonia removal.
Major Offender List
Remember that under ideal conditions the surviving nitrifiers can reproduce more rapidly and conceal the influent toxic impact. Under less than ideal conditions (often lower temperatures or low DO), the impact is magnified by low nitrifier reproduction rates.
Most biological waste aeration basins have some foam. When this foam builds beyond tank walls, it can cause problems with neighboring areas. If it is highly stable, the foam can float on the secondary clarifier and create problems with effluent TSS. In response to recent questions on foaming, I want to cover the basic types I have seen in both municipal and industrial systems.
this is the typical light foam seen on basins. The foam is created by biological byproducts including proteins, polysaccharides, and biosurfactants that are an integral part of microbial activity. This foam tends to be white to light brown in color and is easily collapsed by a water spray. When starting up a new aeration tank, it is common to see more foam as rapidly dividing microbes tend to produce more of the cellular by products than a more stable, decline phase growth system. To combat foaming during startup or with increased loadings, it is often good to add an anti-foam product. As with any chemical addition, the product can be jar tested on site to find the best match for temporary foam control.
Fat, Oil & Grease Foam
Systems receiving food processing, dairy, or petrochemical wastes have hydrophobic components that are quantified by a FOG test. While the compounds alone tend to build a more stable foam, microbes tasked with degrading FOG compounds produce biosufactants to solubilize organics for transport across the cell wall. Often these systems require frequent additions of anti-foam, although new aeration and mixing settings/equipment can minimize the need for chemical addition.
In surfactant manufacturing and in other plants following cleaning or fire fighting (foam use), we often see a highly stable, white foam on the aeration basin. Unlike biological foams, a surfactant based foam is not easily reduced with a water spray and requires anti-foam for control.
Nocardia & Filament Foams
Some wastewater organisms have hydrophobic polymers that create a “greasy”, brown, scum/foam that can be a huge problem on aeration basins. Usually called “nocardia foam” after one of the most common microbial forms causing the foam, control often requires several steps. First the foam contains the microbes so normal wasting is not completely efficient in reducing the offending microbes. A more manual foam skimming, RAS chlorination, and anti-foam program are often required. Long term control can be maintained by reducing FOG reaching the system and lowering sludge age.
Substitutes for Antifoams
In two of the cases above, microbial activity was the direct cause of foam. At Aster Bio we have worked on numerous systems with a tendency to foam and with high proportion of influent FOG. While the anti-foam or chlorination (filament based foams) are quick fix patches, long run control means getting the biomass at a state suited for the influent. We have found that adding bioaugmentation cultures can help mature the biomass and add high numbers of organisms with the ability to degrade target compounds such as surfactants and grease. In cases with Nocardia, the bioaugmentation cultures used along with chlorination of the RAS can help move the balance toward desirable microbes. In all cases, it is more complex than just adding the bioaugmentation cultures. Key factors include an understanding of the causes and changes that can be made to help control the foam along with adding bioaugmentation cultures or other chemicals.
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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