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How can I control algae blooms without dyes or copper sulfate?

1/27/2015

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:

Keep excess nutrients out of the water – both nitrogen and phosphorus can trigger algae blooms. By using judicious fertilizer application, planted zones near the ponds to adsorb nutrients, and physical barriers where necessary; operators can keep the nutrients from reaching the water and therefore preventing algae blooms before they start.

Add a mixer – mixing the water creates a more natural water environment where water turnover reduces eutrophication by encouraging a balance between algae and other life. The mixing prevents anaerobic zones and excessive sludge which can act as a nutrient sink for algae blooms during summer months.

Biological additives (including barley) – in general biological additives include stabilized bacteria that degrade organics form plants and animals found on the pond bottom and water column. In doing so, the bacteria consume excess nutrients and clear the water. In waters with moderate excess nutrients, adding bacteria alone can be a perfect solution. My company, Aster Bio, has used a multiple Bacillus blend with Pseudomonas for nitrate removal on a rice bran carrier to control algae in these applications with good success.

In system with higher levels of nutrients, it may be necessary to add copper sulfate during peak algae growth months. By using the other options first, operators an significantly reduce the amount of copper sulfate applied.

Why are solids are floating on my secondary clarifier?

1/14/2015

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:

Denitrification – small nitrogen gas bubbles float the sludge in the clarifier creating floating sludge chunks with small bubbles entrapped
Fats, Oils & Grease – simply put, FOG floats on water. When entrapped in floc, excessive grease or oil can cause floating biomass. This appears as a scum blanket that can cover the entire clarifier.
Viscous bulking or billowing sludge – viscous bulking can sometimes create floating sludge (more often it is just billowing over the weir versus floating). This is often caused by nutrient deficiencies (normally low phosphate) in industrial waters.

Solutions to floating sludge:

Denitrification problems can be often controlled by increasing the recycle pump to reduce sludge blanket depth/sludge retention time in the clarifier. The problem is often related to an increase in influent ammonia/nitrogen that is converted by beneficial nitrifiers into NO2 or NO3 via the autotrophic nitrification process. Without an anaerobic/anoxic step that removes NO2 or NO3 in the treatment system, this process occurs in the clarifier. Long run solutions include evaluating influent TKN/ammonia, anoxic denitrification zone residence time, availability of “food” or easily available BOD in the anoxic zone for denitficiation, and an overall system survey on sludge age, residence times, and influent makeup.
Fats, Oils & Grease – FOG created floating sludge involves a messy control process. First the scum/floating sludge needs to be removed or allowed to carry over the weir to polishing/tertiary treatment. Upstream, operators need to evaluate where the FOG increase originated. This can be a one-time slug or increased loadings of grease over time. It is best to prevent oils and grease from entering the biological treatment system. In cases where we have high levels of FOG in a system we encourage operators to increase wasting rates (remove entrapped FOG this way) and add cultures associated with FOG degradation/biosurfactant production. By using wasting and seeding steps together, the potential for significant biomass reduction is prevented while removing entrapped FOG that causes high effluent solids.
Viscous Bulking – solution here is to evaluate changes in influent makeup and changes in the environmental conditions in the biological treatment unit. While researching the exact cause of the bulking, operators need to begin wasting the bulking, viscous sludge. If nutrient residuals are low (<1.0 mg/L ammonia nitrogen or <0.5 mg/L ortho-phosphate) then begin adding nutrients to achieve residuals above the targets above. If heavy wasting is involved, we recommend adding cultures to promote the shift to a desirable biomass.

Bio-based industrial cleaners

1/12/2015

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:

Improved removal of stains in tile grout
Reduction in slip hazard caused by fatty acid film left by traditional cleaners
Pest reduction (drain flies specifically) that breed on residual organics in floor drains
Fewer plumber call outs related to grease clogging lines

With parking lots and concrete pads, bio-based cleaners can reduce the need for strong acids or bases while also lowering reliance on solvents. The bio-based product contains biosurfactants as a booster to the chemical surfactants/solvents. On parking lots, we note the following improvements over traditional cleaners:

Improved stain removal with multiple applications
Reduction in hydrocarbons in water collected in storm water retention basins
Less risk to employees as the product had a more neutral pH than other cleaners

Biofilters - remove hydrogen sulfide (H2S) from air at lift-stations and headworks

1/7/2015

Source: Cheresources.com

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.

How can I control algae blooms without dyes or copper sulfate?

Why are solids are floating on my secondary clarifier?

Bio-based industrial cleaners

Biofilters - remove hydrogen sulfide (H2S) from air at lift-stations and headworks

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