Water Treatment Chemicals Selection Guide

Water Treatment Chemicals Selection Guide

Choosing the right water treatment chemicals is critical for both performance and cost-efficiency. This comprehensive guide helps you select the optimal coagulant, flocculant, and specialty chemical for your specific application.

1. Coagulant Selection Guide

Coagulants Comparison Table

Property	PAC (Polyaluminium Chloride)	Aluminum Sulfate (Alum)	PFS (Polyferric Sulfate)	PAFC (Polyaluminium Ferric Chloride)
Al₂O₃ / Fe₂O₃ Content	28-30% Al₂O₃	14-16% Al₂O₃	18-22% Fe³⁺	27-29% Al₂O₃ + 1-3% Fe
Effective pH Range	5.0-9.0	6.5-8.0	6.0-9.0	5.5-9.0
Cold Water Performance	Good	Poor	Moderate	Good
Floc Formation Speed	Fast	Slow	Very Fast	Fast
Floc Density	Medium	Light	Dense	Medium-Dense
Sludge Volume	Low	High	Medium	Low
Color Removal	Good	Fair	Excellent	Good
Phosphorus Removal	Moderate	Low	Excellent	Good
COD Removal	Moderate	Low	Good	Good
Residual Metal Risk	Low	Moderate	High (iron color)	Low
Corrosivity	Low	Moderate	High	Low-Moderate
Cost per Treated Volume	$-$$	$$	$-$$	$-$$
Best Applications	General purpose, drinking water, industrial wastewater	Budget-sensitive, warm climate	High-color, high-phosphorus, industrial	Wide-range applications needing both Al & Fe

Quick Coagulant Selection by Application

Application	Recommended Coagulant	Typical Dosage (mg/L)	Notes
Drinking Water	PAC (drinking water grade, basicity 60-75%)	10-30	NSF/ANSI 60 certified
Municipal Wastewater	PAC + PAM combination	30-100 PAC + 1-3 PAM	TCost-effective for large volumes
Industrial Wastewater (General)	PAC (industrial grade, basicity 70-85%)	50-200	Higher basicity for better performance
Textile/Dyeing Wastewater	PAC + Cationic PAM	200-500 PAC + 2-5 CPAM	Pre-treat with COD remover for high COD
Paper Making Wastewater	PAC or PAFC	100-300	PAFC offers better color removal
Mining Wastewater	PFS + Anionic PAM	100-500 PFS + 1-3 APAM	PFS handles heavy metals well
Oil & Gas Produced Water	PAC + CPAM + PAC	100-300 + 2-5	May need demulsifier pre-treatment
Food Processing Wastewater	PAC (drinking water grade)	50-150	Iron-free to avoid color issues
Swimming Pool	PAC or Aluminum Sulfate	5-15	Alum preferred for budget pools

2. Polyacrylamide (PAM) Flocculant Selection Guide

PAM Types Comparison

Property	Anionic PAM (APAM)	Cationic PAM (CPAM)	Nonionic PAM (NPAM)
Ionic Charge	Negative (-)	Positive (+)	Neutral (0)
Molecular Weight Range	8-25 million	5-15 million	5-15 million
Optimal pH Range	7-14 (alkaline)	4-8 (acidic to neutral)	4-9 (wide range)
Best Paired With	PAC, PFS, PAFC	PAC, PAFC	PAC, PFS
Typical Dosage	1-5 mg/L	2-5 mg/L	1-5 mg/L
Best For	Mining, mineral processing, alkaline industrial wastewater	Sludge dewatering, organic-rich wastewater, municipal sewage	Acidic wastewater, special industrial processes
Water Solubility	Good	Moderate (needs longer mixing)	Good
Cost	$	$$	$

PAM Selection Decision Flow

1. Determine wastewater pH: Alkaline → APAM; Acidic → CPAM or NPAM; Neutral → Test all three
2. Analyze suspended solids charge: Negative charge (most common) → CPAM; Positive charge → APAM
3. Identify primary goal: Sludge dewatering → CPAM; Clarification → APAM or NPAM
4. Run jar tests: Test 2-3 types at 1, 2, 3, 5 mg/L each
5. Optimize: Select type and dosage giving clearest supernatant and fastest settling

3. Activated Carbon Selection Guide

Property	Coconut Shell Activated Carbon	Coal-Based Activated Carbon	Powdered Activated Carbon (PAC)
Iodine Number (mg/g)	900-1200	800-1000	700-1000
Surface Area (m²/g)	1000-1300	800-1100	700-1200
Hardness (%)	≥98	≥95	N/A (powder)
Ash Content (%)	≤3	≤10	≤5
Best For	Drinking water, food & beverage, pharmaceutical	Industrial wastewater, municipal water	Emergency treatment, seasonal applications
Regeneration	Multiple cycles	Multiple cycles	Single use
Cost	$$	$	$-$$

4. Filter Media Selection Guide

Filter Media	Effective Size (mm)	Primary Function	Typical Filter Depth	Replacement Cycle
Quartz Sand	0.4-1.2	Turbidity removal, general filtration	400-700mm	3-5 years
Anthracite	0.8-2.0	Organics removal, dual-media top layer	300-500mm	5-8 years
Manganese Sand	0.6-2.0	Iron & manganese removal	800-1200mm	5-10 years
Activated Carbon	0.5-2.0	Organics, chlorine, taste & odor	500-1500mm	1-3 years

5. Specialty Chemicals Selection

Problem	Recommended Product	Typical Dosage	Expected Performance
High COD	COD Remover	100-1000 mg/L	60-85% COD reduction
High Ammonia Nitrogen	Ammonia Nitrogen Remover	50-500 mg/L	70-95% NH₃-N removal
Heavy Metal Contamination	Heavy Metal Capture Agent (DTC type)	10-100 mg/L per mg/L metal	Cu, Ni, Zn, Cr, Pb to below 0.5 mg/L
High Phosphorus	Phosphorus Removal Agent (Fe/Al salt)	50-300 mg/L	Total P to below 0.5 mg/L

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