H2S Odor Abatement & Concrete Sewer Corrosion (MIC) Control Using Ferrous Chloride FeCl2 30% Combined with Hydrogen Peroxide H2O2 50%

Table of contents

Eliminating toxic Hydrogen Sulfide (H₂S) gas and halting Microbiologically Induced Corrosion (MIC) in industrial wastewater collection networks requires chemical intervention directly within the liquid phase before H₂S can strip into the air. By injecting Ferrous Chloride FeCl₂ 30% at upstream lift stations (15–18 g FeCl₂ 30% / m³ per 1 mg/L S²⁻) to precipitate sulfide as insoluble FeS (Ksp = 6.3 × 10⁻¹⁸), combined with polishing doses of Hydrogen Peroxide H₂O₂ 50% at the equalization basin inlet, treatment plants eliminate 95–99% of airborne H₂S (≤ 0.5 ppm in worker breathing zones), protect concrete infrastructure, and enhance primary clarification.

Actual 30kg jerrycan of Ferrous Chloride FeCl2 30% directly manufactured by Loc Thien Chemical

1. Anaerobic Sulfate Reduction, pH-Dependent H₂S Stripping & Concrete Crown Corrosion (MIC)

Wastewaters from textile dyeing (rich in Na₂SO₄ electrolyte), Kraft pulp and paper mills, tanneries, seafood processing, tapioca starch, and rubber latex contain 300 to 2,500+ mg/L of Sulfate ions (SO₄²⁻). Inside anaerobic force mains, deep collection sumps, and un-aerated equalization tanks (DO ≤ 0.2 mg/L, ORP ≤ -150 mV), Sulfate-Reducing Bacteria (SRB — Desulfovibrio) reduce SO₄²⁻ into total dissolved sulfide (S²⁻, HS⁻, H₂S):

Anaerobic SRB Reduction: SO₄²⁻ + 2CH₂O + 2H⁺ → H₂S (aq) + 2CO₂ + 2H₂O
Aqueous Dissociation Equilibrium (pKa1 = 7.0 at 25 °C): H₂S (aq) ⇌ H⁺ + HS⁻
- At pH = 6.0: 91% of dissolved sulfide exists as volatile H₂S gas that rapidly strips into the headspace at drop manholes and pump sumps.
- At pH = 7.0: 50% exists as volatile H₂S gas and 50% as non-volatile HS⁻.
- At pH = 8.5: Less than 3% remains as volatile H₂S gas (97% stays locked in solution as HS⁻).

Airborne `H₂S` Concentration (`ppm`)	Human Physiological & Occupational Safety Impact (OSHA / NIOSH)	Concrete Sewer Crown Corrosion Rate (`Biogenic H₂SO₄ Attack`)
`0.01 – 0.3 ppm`	Odor threshold (characteristic rotten-egg smell triggering community complaints).	Negligible structural damage.
`10 – 20 ppm`	`OSHA PEL Ceiling = 20 ppm`. Eye conjunctivitis and respiratory tract irritation.	Thiobacillus bacteria colonize damp concrete crown surfaces.
`50 – 100 ppm`	Olfactory Fatigue (paralysis of sense of smell) within `3–15 minutes`—workers falsely believe gas has cleared!	Concrete crown surface `pH` drops to `1.5–2.2`; mortar loss `2–4 mm/year`.
`300 – 500 ppm`	Immediately Dangerous to Life or Health (`IDLH = 100 ppm`); pulmonary edema within `30 minutes`.	Cement paste converts into non-structural Gypsum mush (`CaSO₄·2H₂O`), exposing rebar.
`≥ 700 – 1,000 ppm`	Instant unconsciousness (“Knockdown Effect”) after `1–2` breaths; fatal without SCBA.	Catastrophic collapse of manhole slabs, pump shafts, and copper electrical panels.

2. Sulfide Precipitation by FeCl₂ 30% & Catalytic Oxidation by H₂O₂ 50%

2.1. Instantaneous Sulfide Locking with Ferrous Chloride (`FeCl₂ 30%`)

Dosing FeCl₂ 30% into sulfide-bearing wastewater drives an instantaneous precipitation of Ferrous Sulfide (FeS) with an ultra-low solubility product (Ksp = 6.3 × 10⁻¹⁸):

Molecular Reaction: FeCl₂ + H₂S → FeS (precipitate ↓) + 2HCl
Net Ionic Reaction: Fe²⁺ + HS⁻ → FeS (precipitate ↓) + H⁺

Within 10–30 seconds of mixing, dissolved H₂S drops below 0.05 mg/L, completely eliminating H₂S vapor pressure above the water surface. When trace Ferric ions (Fe³⁺ or co-dosed Ferric Chloride FeCl₃) are present, Fe³⁺ oxidizes H₂S to elemental sulfur (S⁰) while reducing to Fe²⁺, which subsequently binds a second HS⁻ ion.

2.2. Polishing Oxidation & Iron Regeneration with Hydrogen Peroxide (`H₂O₂ 50%`)

At Neutral / Slightly Acidic pH = 6.0 – 7.8: H₂O₂ + H₂S → S⁰ (colloidal ↓) + 2H₂O (1.06 kg H₂O₂ 100% / kg H₂S).
At Alkaline pH ≥ 8.0 – 9.0: S²⁻ + 4H₂O₂ → SO₄²⁻ (soluble) + 4H₂O (zero suspended solids generated).
Synergistic Dual FeCl₂ + H₂O₂ System: Trace Fe²⁺ catalyzes H₂O₂ oxidation of H₂S (5–10× faster reaction, finishing in 1–3 minutes), while H₂O₂ re-oxidizes FeS to regenerate active iron ions, reducing total chemical cost and iron sludge volume by 30–40%.

Actual 35kg jerrycans of Hydrogen Peroxide H2O2 50% at Loc Thien Chemical warehouse

3. Dosing Rate Comparison & 3,000 m³/day Engineering Calculation

Table 2: Technical Comparison of H₂S Control Regimes in Industrial Wastewater

Technical Criterion	Ferrous Chloride (`FeCl₂ 30%`)	Hydrogen Peroxide (`H₂O₂ 50%`)	Synergistic Dual System (`FeCl₂ 30%` + `H₂O₂ 50%`)
Primary Reaction Mechanism	Selective precipitation (`FeS ↓`)	Oxidation to `S⁰` or `SO₄²⁻`	Upstream sulfide locking + Downstream catalytic oxidation
Reaction Time Required	Instantaneous (`≤ 10 – 30 sec`)	`15 – 30 minutes` (uncatalyzed)	Ultra-fast (`≤ 1 – 3 minutes`)
Theoretical 100% Basis / `1 kg S²⁻`	`3.96 kg FeCl₂ (100%)`	`1.06 kg H₂O₂ (100%)` (at pH 7)	`2.2 kg FeCl₂ (100%) + 0.6 kg H₂O₂ (100%)`
Practical Commercial Dosage / `1 kg S²⁻`	`15.0 – 18.5 kg FeCl₂ 30%` (`11.7 – 14.4 L`)	`2.6 – 3.5 kg H₂O₂ 50%` (`2.2 – 2.9 L`)	`8.5 kg FeCl₂ 30%` + `1.4 kg H₂O₂ 50%`
Optimal Injection Point	Upstream lift station, force main inlet	Equalization tank inlet, pre-DAF channel	`FeCl₂ 30%` at lift station + `H₂O₂ 50%` at EQ tank inlet
Co-Benefits for WWTP	Coagulant aid for color, Phosphate (`PO₄³⁻`), and `25–35%` COD removal	Boosts Dissolved Oxygen (`DO`) without increasing TDS salinity	`≥ 99%` odor elimination, `35%` less iron sludge, protects aerobes

Technical Illustration (Reference Engineering Model): A packaging paper and textile wastewater plant treats Q = 3,000 m³/day (125 m³/h) containing C(S²⁻) = 28 mg/L (84.0 kg S²⁻/day), generating 85 ppm airborne H₂S above the equalization sump.

Option 1 (FeCl₂ 30% Standalone at 16.0 kg / kg S²⁻): 84.0 × 16.0 = 1,344 kg FeCl₂ 30%/day (43.75 L/h).

Option 2 (Combined FeCl₂ 30% at 8.5 kg/kg + H₂O₂ 50% at 1.4 kg/kg): 714 kg FeCl₂ 30%/day (23.2 L/h) at the upstream lift station + 117.6 kg H₂O₂ 50%/day (4.10 L/h) ahead of the equalization tank—reducing dissolved S²⁻ to ≤ 0.2 mg/L and airborne H₂S to ≤ 0.3 ppm within 45 minutes.

4. Direct Manufacturer of FeCl₂ 30% & ZDHC MRSL v3.1 Certified Supply by Loc Thien Chemical

Loc Thien Investment Development Co., Ltd. (LOC THIEN INVESTMENT DEVELOPMENT COMPANY LIMITED — Tax ID: 0313650856) offers a unique dual capability in Vietnam’s environmental chemical sector:

Strict SSOT Product Positioning:
- Direct Manufacturer: Loc Thien is the DIRECT MANUFACTURER of FeCl₂ (exclusively 30% aqueous solution) and wastewater-grade Ferric Chloride (FeCl₃) in Vietnam.
- Commercial Supplier: Loc Thien is a TIER-1 COMMERCIAL SUPPLIER & DISTRIBUTOR of H₂O₂ 50% and other industrial chemicals (NaOH, HCl, H₂SO₄, PAC, NaOCl).
Synchronized ZDHC MRSL Version 3.1 Conformance Level 1 Credentials:
- FeCl₂ (Ferrous Chloride): Holds ZDHC MRSL Version 3.1 Level 1 Conformance Summary Report (CSR) No. 248162921-02 and Analytical Test Report No. 248162921-02a issued by TÜV Rheinland Vietnam (22–23/10/2024).
- H₂O₂ (Hydrogen Peroxide): Holds CERTIFICATE (ZDHC MRSL Conformance Level 1) No. ZDHC1 127736 0002 Rev. 00 (Test Report No. 2486017673-Q24VPS-CHM2869) issued by TÜV SÜD Product Service GmbH / TÜV SÜD Vietnam.
6 Warehouses (3,000+ tons/month, 5–30-ton tanker fleet) & Delivery SLA: Ba Ria - Vung Tau (Phu My 1 IP), Dong Nai (Long Thanh IP), Binh Duong (Di An City), Da Nang (Hoa Khanh IP), Can Tho (Tra Noc IP), and Bac Ninh (Tien Son IP). Headquarters: 452/6B Tinh Lo 10, Binh Tri Dong Ward, Binh Tan District, Ho Chi Minh City. Technical quotation within 15 minutes; delivery within 4 hours in inner HCMC, 24–48 hours across Southern & Mekong Delta industrial zones, and 2–3 days in Northern & Central Vietnam. Contact hotline 0979 891 929 for detailed delivery procedures.

Product Pages: Ferrous Chloride FeCl₂ 30% (Direct Manufacturer) | Hydrogen Peroxide H₂O₂ 50% | Ferric Chloride FeCl₃ 38%–40%
GHS Safety Data Sheets (MSDS): MSDS Ferrous Chloride FeCl₂ 30% | MSDS Hydrogen Peroxide H₂O₂ 50%
Technical Inquiry & 15-Minute Quotation: Hotline 0979 891 929 (tel:0979891929) — Email: [email protected].