Municipal Water & Wastewater Treatment Solutions

Meeting Stringent Discharge Limits/Reducing Plant Operational Cost

Meeting water/wastewater effluent standards is critical for municipalities. Treatment plants are faced with the challenges of a growing population/demographic shifts, changing regulations, failing infrastructure, or outdated treatment technology.  Sciential’s test kit and testing services aid consults, original equipment manufacturers (OEM) and end-users answers to their municipal wastewater treatment challenges. Sciential’s test kits provide easy to use and reliable performance to help determine the flowsheet, capital expenditure (CapEx), operational expenditure (OpEx) and process performance values to meet strict discharge limits in the water reuse, wastewater treatment, and tertiary water treatment for every state, county, city, town or locale.

 

Treatment Drivers

Water Wastewater
Naturally Occurring Organics (NOM), Disinfection by-products, TTHM – 80 mg/L, HAA5 – 60 mg/L

Arsenic – MCL 0.010 mg/L

Nitrate – MCL 10 mg/L N

Uranium – MCL 30 mg/L

Chrome – MCL 10 mg/L (VI)

Perchlorate – MCL 6 mg/L

Color – 15 CU (SMCL)

Iron – 0.3 mg/L (SMCL)

Manganese – 0.05 mg/L (SMCL)

Uranium – 30 ug/L

TSS/Turbidity

 

TSS/Turbidity

TDS

BOD

NOM

Heavy Metals

Persistent Organic Pollutants (POP)

Nitrate

Phosphorus

Hardness

Color

 

Maximum Contaminant Level (MCL), Secondary Maximum Contaminant Level (SMCL)

 

Treatment Examples

Surface Water Pretreatment

The surface water pretreatment prepares water for use in any type of treatment plant and is needed when the source of water comes from a raw/ contaminated source (usually river water) where the total suspended solids (TSS) should range from 50 mg/L – 200 mg/L.  Treatment consists of four steps: chemical pretreatment, clarification, filtration, and sludge treatment

 

Chemical Pretreatment

Sodium hypochlorite (bleach) is added to kill any living organisms that may be in the raw water. Coagulant helps particles come together to improve clarity and settling. Polymer turns individual particles into larger clusters. The larger particles settle faster and form a more concentrated sludge.

 

Clarification

After the chemical pretreatment, the water flows into the solids contact clarifier.  The solids contact clarifier  is used when there are not enough solids in the feed water source to flocculate on their own or as solids seeding to facilitate fine particle sweeping (clarifying) and/or for improved setting characteristics.  Settled solids from the bottom of the clarifier are mixed with the incoming feed water. The particles intimately interact and form larger particles for faster settling characteristics.  The clarified water (effluent) reports to an effluent trough and settled the solids (sludge) are scraped to the center clarifier and removed for further dewatering. If conditioned properly, the overflow (effluent) can produce less than 10 mg/L of total suspended solids.

 

Filtration

If necessary, the overflow can be treated by filtration. The water starts by going into an equalization tank that allows for a constant flow into the single or multi-media filter.  As the water flows from the equalization tank to the media filter, polymer may be added to improve filtration performance. The resulting water TSS is now less than 1mg/L. It may be directly sent to a cooling tower or it can be further filtered depending on the intended use.

 

Sludge Treatment

The underflow solids from the clarifier (i.e., conventional, solids contact, inclined plate) is pumped into a thickener.  Flocculant is added to improve the solids settling rate (flux) and effluent clarity. The thickened underflow is sent to a pressure filter (plate and frame) or belt press or vacuum dewatering filter.

Thickened solids are pumped to a pressure filter at a 100 psi into a chamber held together by two plates.  Once the filtrate rate reaches a terminal flow rate (usually 10% of the initial flowrate), the pressure is released and the formed cake solids are dropped and the filter closed and operation commences.

The belt press is usually flocculated and placed either in a rotary drum concentrator or gravity drain deck.  The thickened solids are then placed between two belts (upper and lower) and squeezes allowing the water to further pressed out through a series of pressure rolls.

If total suspended solids are <50 mg/L than water should go straight to a filter. If >200 mg/L, should go to a standard clarifier.  Cold lime softening might be considered for water hardness above 150 mg/L as CaCO3.