Algae blooms are a problem in many areas where nutrient runoff coupled with sunlight can trigger excessive algae growth. While algae is needed in healthy waters to provide oxygen and food for animals, an algae bloom can cause problems with appearance, odors, and even be toxic to animals.
In this post I am going to concentrate on retention ponds, small decorative lakes, and water features. As these are usually close to housing and offices, algae control is of utmost importance. Most commonly, I see the ponds maintained using aerators, dyes, and copper sulfate. The direct expense and the pressure to reduce chemical applications has many maintenance departments wanting a new approach for algae control.
While many companies say adding bacteria can control algae by itself, I find these cases an exception rather than the rule. What I encourage clients to do is the following:
Secondary clarifiers can be running smoothly one day and then suddenly solids begin to float and carry over the weir into the effluent. What are the conditions that cause floating sludge? And more importantly, what can be done to control it.
First floating sludge is most often caused by:
Solutions to floating sludge:
The first generation of bio-based cleaners utilized enzymes such as protease to improve laundry detergent performance. As enzyme production technology improved, detergent formulators began to add amylase, lipase, and other more specialized enzymes to their formulations. In the cleaner market, enzymes help boost surfactant performance by enhancing the water solubility of target compounds. With improved solubility, the compounds are efficiently washed away in the water.
While enzymes are effective in laundry detergents and even dish washing cleaners, institutional floor cleaners and heavy-duty concrete cleaners benefit from the addition of microbes in addition to the standard enzyme package. In the case of restaurant floors, we have evaluated a highly biodegradable surfactant package blended with biosurfactants, enzymes and preserved microbes. The benefits from this package over the surfactant only cleaner was:
Increasingly common at large lift stations and treatment plant headworks, biofilters have the ability to reduce concentrations of H2S and other odor causing gases at a lower cost than competing control technologies.
In all cases, biofilters rely on the ability of microbes to covert odors and hazardous compounds into less problematic forms.
The most discussed conversion by Thiobacillus sp, Thiosphera, & Paracoccus sp. Is the following:
H2S + 2 O2 --> H2SO4
The microbes also have the ability to neutralize odors from other organic sulfur compounds including mercaptans. In the case of Thiosphaera and Paracoccus sp, the microbes can also utilize volatile organic acids such as acetic, butyric and propionic acids.
While we often focus on the engineering aspects including residence time and specific filter media, the microbes are often considered as ubiquitous and should be present at all times. In my experience, the population makeup and concentrations vary significantly based on pH, temperature, and inlet gas makeup. There are seasonal and site specific variations that can cause problems maintaining maximum removal efficiency.
First the general design parameters are (from Metcalf & Eddy Wastewater Engineering):
Moisture 50 - 65%
Temperature 15 - 35oC
pH 6 - 8
Res. Time 30 - 60 seconds
H2S Removal 80 - 130 g/m3 per hour
Other Odor 20 - 100 g/m3 per hour
In operating the filters, the moisture is maintained with a spray/pump system. The water contains added nutrients (N &P) and alkalinity supplements to maintain the biomass in ideal conditions.
Treatment issues can occur with low removal efficiency at startup, increased loadings (summer temperatures), during seasonal temperature changes at the filter itself. While the biomass will eventually adjust and reach a steady-state, the time lag can cause issues for operators.
To reduce the time lag and help with periodic losses in efficiency, I propose the owners of trickling filters evaluate adding sulfur oxidizing cultures directly to their biofilters. Over the past decade, I have worked with multiple strains of Thiobacillus, Thiosphaera, and Paracoccus for use in sulfide containing wastewater streams. All are well adapted for growth in biofilters and can help increase the population of active microbes without the normal lag time seen as indigenous microbes grow.
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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