Primary Treatment

  • Hydro International
  • Monroe Environmental

Hydro International


The Hydro MicroScreen™ is a low-energy, small-footprint rotating belt screen that delivers exceptional solids removal from process water and wastewater. Maintaining efficiency even at peak design flow rates, it enables operators to meet discharge requirements, increase efficiency and save money.

With screen sizes available from 50-2,000 µm that handle flows up to 3.1 MGD in a single unit, typical performance is:

  • Removal of 60-70% TSS, 30-40% BOD & 30-40% FOG
  • Total phosphorus reduction up to 10%
  • Discharged solids directly off screen are 2-4% TS
  • Can produce 30-50% TS when equipped with dewatering section and compression zone (no chemical addition)

Monroe Environmental

Circular Clarifiers

Monroe Environmental's primary circular clarifiers are designed to receive raw wastewater after it has been pre-screened to remove large objects and grit. This primary wastewater treatment sedimentation tank will produce a homogeneous liquid capable of being treated biologically and a sludge that can be separately treated or processed.

Clarifier Influent

  • Sufficient tank size and low energy inlet geometry allows sludge to settle and floating solids and oils to rise to the surface.
  • If a standard center inlet design will not provide full flocculation of the suspended solids, an energy-dissipating inlet (EDI) will be utilized. This type of inlet distributes the flow into the flocculation zone and imparts a tangential stirring action that decreases settling time. 
  • Monroe is able to furnish a variety of EDI designs depending on customer requirements and influent characteristics.
  • Mechanical flocculation and treatment with chemical coagulants are available, depending on the application. An enlarged feedwell for enhanced flocculation can be designed to provide increased residence time that aids floc formation and improves settling.

Drives and Sludge Collection

  • Monroe Environmental incorporates durable drives and bottom scraping rakes that will continuously remove settled sludge. The rake employs multiple bottom scraping blades that are angled to ensure that all settling sludge is captured and brought to the central sludge well. Spiral scrapers may be employed as well in place of traditional plough and furrow scrapers.
  • Monroe offers both cast iron worm gear and fabricated steel precision gear drive assemblies.
  • Truss type or cable-supported rake mechanisms are available.

Skimming and Scum Removal

  • Floating matter in primary wastewater clarifiers includes grease, oils, leaves, and plastics.
  • Typically, floating matter is skimmed by a skimmer arm that is supported by the sludge rake and rotates with it around the tank. The floating matter is pushed over the beach plate by the wipers attached to the skimmer arm and into a scum box attached to the tank wall. Collected material then travels to the scum outlet piping. A ducking skimmer system is also available with fixed, full radius collection troughs.
  • The unique design of the Monroe 3-axis pivoting scum wiper blade ensures constant contact with the scum beach, providing the highest scum removal efficiency possible.

Clarifier Effluent

  • A scum baffle prevents floating matter from reaching the effluent launder. Proper dimensions and positioning of the baffle prevents carryover.
  • An appropriately sized V-notch weir assures uniform laminar flow throughout the clarifier.
  • Monroe offers weirs, baffles, and launders in a variety of construction materials inclusing stainless steel, FRP, aluminum, and galvanized steel.
  • Density current (Stamford) baffles and launder covers are available when required.
  • The effluent is essentially homogeneous and ready for aeration and biological treatment.
Primary Scrape Clarifier Torque Sludge Thickener

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