Phosphorus (P) control / removal in wastewater is fast becoming a critical objective for many municipal and industrial wastewater treatment plants. State and Federal regulatory agencies are acting with increasing urgency to limit point source and non- point source discharge of nutrients (phosphorus, nitrogen) as a means to lessen the harmful effects of algal blooms on the environment. Mitigation of point source phosphorus discharge from wastewater treatment facilities is usually achieved via biological and or chemical means. USALCO is uniquely positioned to provide wastewater plant personnel, as well as consulting engineers, with the necessary technical support and effective chemistries to help identify the best solution to achieve nutrient removal goals.
Impact of Excess Phosphorus
In nature pure “elemental” phosphorus is rare. It usually exists as both inorganic and organic phosphate originating from various natural and human sources (fertilizer, livestock waste, outdated sewage/septic systems, cleaning products). High levels of phosphorus and other nutrients, such as nitrogen, can create harmful water quality conditions. Both are essential nutrients for aquatic plant growth. However, when said nutrients are available in excess a body of water can become “eutrophic” or “well fed.” Eutrophication or excess algae growth can potentially result in the following:
- Unsightly growth and odor
- Depletion of oxygen that damages aquatic live
- Toxins, such as microcystin, which can jeopardize public health (human contact,water supply)
Chemical Reaction and Removal
Historically aluminum (Al+) or Iron (Fe+) based chemicals have been used to remove soluble phosphorus by creating a settleable solid. The long held view that these metals precipitate phosphorus is no longer supported by recent research which details a different mechanism of reaction. Instead it is believed that aluminum reacts with the natural alkalinity in water to form a hydrous metal oxide (HMO) floc. Soluble P absorbs to HMO reactive sites while insoluble P (colloidal and particulate) is entrapped in the floc.
Chemicals typically used for P removal over the years include aluminum chloride, aluminum sulfate (alum), polyaluminum chloride (PACL), sodium aluminate, ferrous chloride and ferric chloride. Time has proven that through research and countless applications significant differences exist between aluminum (Al+) and Iron (Fe+) based P removal agents:
- A molecule of aluminum weighs less then half of a molecule of iron, therefore at equal dosage aluminum will react with twice as much phosphorus (lower metal /P molar ratio)
- Iron negatively effects UV disinfection efficacy and economics by absorbing UV light in critical wavelengths
- Iron salts such as ferric/ferrous chloride are more corrosive, messy, and negatively impact UV bulbs as well as chemical storage/feed equipment
- The iron based HMO floc will release phosphorus under anoxic conditions
USALCO® Performance Chemistries for Phosphorus Compliance
USALCO has several product offerings that are highly effective for phosphorus control in wastewater treatment plants where discharge limits are set by federal, state, or local regulations. They are:
- Sodium Aluminate (LSA 38)
- Aluminum Sulfate
- DelPAC® (polyaluminum chloride)
- DelPAC XG (aluminum chlorohydrate)
- Aluminum Chloride
Depending on the application, our aluminum chemicals will outperform iron salts at a lower overall cost. USALCO recognizes that each situation is unique and our representatives can assist you in selecting the best product for your application through technical audits and bench testing.
One such product, sodium aluminate (LSA 38), is unlike all other P removal chemistries which are acidic to varying degrees. Sodium Aluminate will not deplete available alkalinity and depress effluent pH below discharge limits.
USALCO phosphorus removal chemicals have been proven to solve problems, add value, and provide cost savings when converting from iron-based salts or starting new permit applications.
USALCO chemistries can provide many benefits which often include:
- Significant reduction in gallons per day chemical requirement
- Reduced or eliminated use of chemicals for pH adjustment, such as sodium hydroxide and lime
- Elimination of negative interference in UV systems where iron was previously utilized, thereby improving energy efficiency
- Improvement of ammonia removal and compliance in systems with deficient or depleted alkalinity.
- Consistent control year round, unlike competitive chemicals whose performance diminishes outside certain pH and or alkalinity ranges
➔ Case Study #1 – Sodium Aluminate resolves seasonal performance issue
➔ Case Study #2 – Restoring compliance and reducing cost
➔ Case Study #3 – Replacing ferrous chloride eliminates metals contamination and associated cost