in Wastewater. Wastewater can be rich in carbon, nitrogen,
and phosphorous contaminants which are essential nutrients for the growth
of organisms. Phosphorus bans on detergents have served to reduce the
levels of phosphorous in domestic wastewater. However, many industrial
and food process waste streams are inherently high in phosphorous content.
The discharge of a phosphorous-rich wastewater into a receiving stream
may stimulate accelerated algal growth, resulting in oxygen depletion
and stream eutrophication.
Traditional methods to remove solids, such as settling, filtration,
and centrifuging, will remove a majority of insoluble phosphorous (P)
species. Removal of the remaining soluble P has been performed in numerous
ways. Under certain conditions, phosphate-accumulating microorganisms
can incorporate P into their cell mass. Unfortunately, this P removal
method fails when the P content is high and the nutrient ratios are
less than optimal.
Other common phosphorous removal methods involve the formation of insoluble
phosphate salts with aluminum or iron salts. The use of alum (aluminum
sulfate) or ferric chloride for P removal has a significant drawback
relating to the acidity of the coagulants that are added to the wastewater.
Since both alum and ferric chloride are quite acidic in nature, they
result in a decreased pH to both the settled solids as well as the effluent
stream. By decreasing the pH, microbial activity in a secondary treatment
system such as a digester (aerobic or anaerobic) or in other secondary
treatment processes will be diminished. In addition, these coagulants
tend to form highly voluminous sludge incorporating a significant percentage
of water. This in turn results in increased solids handling and hauling
A new method being discussed for P removal from wastewater involves
the directed formation of struvite, an insoluble magnesium ammonium
phosphate salt. Struvite formation in wastewater treatment plants is
a relatively common but usually undesirable phenomenon, which commonly
results in the clogging of wastewater pipes in areas of high flow velocity.
This new approach requires the addition of new solids separation equipment
a large capital investment in less than fully proven technology. More
importantly, this approach can require modifications that will adversely
affect the primary or secondary treatment processes in order to optimize
the Mg, NH3, and P ratios for tertiary struvite formation and removal.
P Removal with an Alkalinity Boost! IER’s
patent pending approach to wastewater P removal is an extension of the
chemistry of the antacids used every day in human digestive systems.
IER’s innovative Amalgam technology begins with a family of proprietary
formulations that contain specialty blends of aluminum and magnesium
additives which serve to fix the soluble P into an insoluble metal salt
compound under alkaline conditions. This results in optimized total
P removal within the primary clarifier solids fraction. Just like Rolaids
or Tums, IER’s Amalgam formulations rely on the gentle buffering
nature of magnesium hydroxide (Milk of Magnesia) and the strong coagulation
benefits of aluminum hydroxide. Amalgam formulations do not just optimize
the removal of soluble phosphorous, but also provide significant reductions
in total suspended solids (TSS) as well as biological oxygen demand
(BOD). In many cases fats, oils, and greases (FOG), and total Kjedahl
nitrogen (TKN) are also significantly reduced.
combining magnesium and aluminum into a single alkaline formulation,
the benefits of each metal are fully realized resulting in optimized
wastewater coagulation as well as alkalinity buffering. Aluminum cations
(Al3+) provide the primary coagulation benefit, through the formation
of the insoluble, polymeric, web-like structure of aluminum hydroxide,
and through the formation of insoluble aluminum hydroxyphosphate. This
resulting compound captures phosphorous within the solids fraction of
the sludge. Magnesium ions (Mg2+) in turn aid in the minimization of
the resulting sludge volume by bonding to organic solids and causing
them to settle without the associated troublesome high water content.
By minimizing the amount of entrapped water in the sludge matrix, the
volume of the sludge is minimized and the sludge density is maximized,
compared with straight iron-based or aluminum-based coagulants. This
attribute of magnesium can result in a great reduction in the overall
volume of sludge requiring disposal from a wastewater treatment facility.
The ratio of the aluminum-based additive and magnesium-based additive
in the Amalgam composition is dependent upon the nature of the wastewater
to be treated. When the primary goal of the treatment is rapid solids
settling, the composition will be more predominant toward the aluminum-based
additive. When the primary goal of the treatment is solids compaction
or pH buffering, the composition will be more predominant toward the
magnesium-based additive. The table below provides examples of the P
removal performance of varying Amalgam formulations applied to the influent
wastewater to a clarifier at a food processing plant.