Meeting Stringent Discharge Limits / Reducing Plant Operational Cost
Municipal Water and Wastewater Solutions
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faced with the challenges of a growing population/demographic shifts, changing regulations, failing infrastructure, or outdated treatment technology.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.
Simulation Test Kits
- Particle size distribution – Sieves stack test unit
- Chemical screening – Bench jar test unit
- Clarification – Bench jar test unit
- Polishing filter – Bench media filter unit
- Thickening– Bench thickener test unit
- Dewatering – Bench vacuum filter or pressure filter
Treatment Drivers
WATER
- 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
WASTEWATER
- 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. Settled solids from the bottom of the clarifier are mixed with the feed water. The particles interact and form larger, faster settling particles. The clarified water flows out the top and the solids (sludge) are scraped to the center and removed for dewatering. The overflow typically has less than 10 mg/L of 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 dual media filter. As the water flows from the equalization tank to the dual media filter, polymer may be added to improve filtration. 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.
Filtration
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 or belt press or vacuum dewatering filter. Thickened solids are pumped at a pressure of 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.