Plan Review for Treatment Plants

What do I need to include in a submittal of treatment plant plans and specifications?

• Purpose of treatment.
• Design capacity, in GPM or GPD (including maximum hours of operation).
• Flow rate for filters.
• Estimated filter run times (between backwashes).
• Raw water contaminant concentrations (iron, manganese, organics, turbidity, hardness, pH, nitrate/nitrite, ammonia, arsenic, radium, etc).
• A civil (scaled) site plan showing the building location, utility locations, site grading, well locations, backwash tanks, and reservoirs.
• A process schematic drawing.
• Scaled process floor plans and section drawings showing all piping and appurtenances with sizes, treatment equipment, basins, chemical storage, chemical injection points, and sample taps.
• A detailed diagram for each chemical feed system.
• Manufacturer name and product name of each chemical used.  All chemicals used for water treatment must be ANSI/NSF Standard 60 approved and listed.
• Calculations for chemical feed rates and sizing of rotameters.
• Provisions for chemical spill/leak containment for all chemicals.
• Mechanical plans showing equipment for plumbing, ventilation, heating and air conditioning, and dehumidification.
• Plumbing floor plans and riser diagrams showing all water supply and waste piping, floor drains, venting, cleanouts, fixtures, water heater, valves, etc.
• Specifications for treatment unit components such as filter media, underdrain, airwash system, and backwash troughs.
• Specifications for all equipment and materials, including manufacturer names and model numbers.
• Procedures for disinfection of the plant (basins and piping) and pressure testing of the piping.
• Electrical plans and specifications for controls and emergency backup power. The electrical plans shall show the location of the emergency generator. The electrical specifications should include the make, model, horsepower, and kilowatt rating of the electrical generator.
• Any plumbing must meet Minnesota Well Code isolation distance requirements.

When is a pilot plant study required?

• When alternate water-treatment technologies (membrane filtration, for example) are used.
• Technologies that have not been used or which are not typically used for the proposed treatment application.

 Where do sample taps need to be installed?

A raw water sample tap must be provided prior to any chemical feed or treatment equipment.  Separate sample taps shall be provided for each individual raw water source.  A sample tap is also required for the finished water.  In addition, sample taps are recommended to be installed on the influent and effluent of each treatment unit (filters, softeners, etc.).  If dual media is used for filtration, it is recommended that sample taps be provided at points between the two media.

What is required when recycling water from a backwash reclaim tank?

• The tank must be constructed in accordance with the requirements for finished water storage tanks in the 10 State Standards for Water Works, part 7.
• A minimum horizontal separation distance of 50 feet must be provided between any part of the tank and buried sewer.
• The sludge waste from the tank must discharge to the sanitary sewer through an air gap. The discharge point must be located at least 50 feet away from any part of the tank.
• The volume of the tank should be sized to hold water from at least 1.5 to 2 backwashes.
• If a wash down system is installed, the water supply for the wash down system must be equipped with an approved backflow prevention device.
• It is recommended that more than one tank compartment be provided.

Can plumbing fixtures such as toilets, lavatories, or mop sinks be installed in a treatment plant?

Yes, but only if the following requirements are met:

• Two separate waste systems are required: one for sanitary soil wastes and one for “grey water” wastes from floor drains that are located in operating areas.
• Any buried sanitary soil waste piping must be located at least 50 feet away from below grade finished water basins.  If a separation distance of at least 50 feet cannot be met, then an additional measure of protection must be provided for the buried sewer pipe.
• The sanitary soil waste and grey water waste systems must discharge separately to a sanitary sewer manhole that is located at least 50 feet from below grade finished water basins, including backwash reclaim basins.  The overflow rim of the manhole must be at least 12 inches below the elevation of the lowest fixture or floor drain served by either drainage system.