Petrochemical Wastewater Treatment
Integrated effluent treatment systems for petrochemical complexes, oil refineries, and downstream chemical plants — managing hydrocarbons, phenols, sulphides, ammonia, and high TDS with API separation, biological treatment, and ZLD capability
Industry Overview
Petrochemical Wastewater Treatment
Petrochemical and refinery wastewater treatment is among the most technically demanding challenges in industrial environmental engineering. A large petrochemical complex generates multiple distinct wastewater streams — process condensates, cooling tower blowdown, desalter brine, sour water from hydroprocessing and cracking units, oil-contaminated runoff from tank farms and process areas, and laboratory drain effluent — each with different characteristics that must be segregated, pre-treated, and combined for integrated treatment before discharge or reuse.
CPCB classifies petroleum refineries and petrochemical complexes as 'Red' category industries under the 17 highly polluting industries notification. These facilities are subject to real-time online effluent monitoring (OCEMS), strict discharge standards for phenols (<1 mg/L), oil and grease (<10 mg/L), sulphides (<2 mg/L), total chromium (<2 mg/L), and increasingly, ZLD mandates for facilities in water-stressed areas or near sensitive ecological zones. The National Green Tribunal (NGT) has issued specific directions on compliance monitoring for petrochemical clusters in Gujarat and Maharashtra.
Spans Envirotech brings multi-technology design capability to petrochemical wastewater treatment — from API/CPI oil-water separation and phenol stripping through anaerobic and aerobic biological treatment to advanced membrane and evaporation systems for ZLD. Our process design for petrochemical clients begins with a detailed site waste audit: stream identification, flow measurement over a 30-day operating period, and comprehensive characterisation before any process selection is made. This discipline matters because petrochemical effluent composition can shift dramatically with feed crude quality changes, unit turnarounds, and seasonal variations.
Industry Challenges
Key Environmental Challenges
Free and Emulsified Hydrocarbons
Crude oil and refined product contamination from process leaks, tank drainage, and equipment washdown. Free oil (100–2,000 mg/L) must be removed before biological treatment. Emulsified oil — stabilised by surfactants and heat — requires DAF with coagulant dosing for effective removal. CPCB limit for oil and grease in treated effluent: <10 mg/L for surface water discharge.
Phenol and Phenolic Compounds
Catalytic cracking, thermal cracking, and coal tar processing release phenol and cresols at 5–500 mg/L. Phenol at concentrations above 50 mg/L inhibits nitrifying bacteria. CPCB discharge limit: <1 mg/L total phenols. Effective removal requires steam stripping for high-phenol streams followed by biological degradation with acclimatised specialised bacteria (Pseudomonas putida, Alcaligenes sp.), and activated carbon polishing.
Sulphides and H2S from Processing Units
Hydroprocessing, hydrotreating, and sour gas operations generate sulphide-laden sour water. Hydrogen sulphide at 10–100 mg/L is acutely toxic, corrosive, and creates explosive atmosphere risks. CPCB limit: total sulphides <2 mg/L. Treatment involves dedicated sour water stripping (SWS) before main ETP, followed by biological oxidation or chemical oxidation of residual sulphide using hydrogen peroxide or chlorination.
High Ammonia from Cracking Operations
Catalytic cracking and hydroprocessing produce ammonia at 50–500 mg/L in process water. Ammonia must be stripped in SWS units and sent for sulphur/ammonia recovery, or biologically nitrified-denitrified in the main ETP. Combined ammonia and sulphide presence creates biological treatment challenges — both inhibit nitrification at elevated concentrations — requiring staged treatment and careful load management.
High TDS from Desalter and Cooling Tower Blowdown
Crude oil desalting generates hypersaline brine (TDS 20,000–100,000 mg/L) from wash water contaminated with crude salt. Cooling tower blowdown carries TDS 3,000–10,000 mg/L from mineral concentration cycles. High-TDS streams suppress biological activity, require separate handling, and are major drivers for ZLD systems — evaporation is needed to concentrate and recover water from these streams.
Catalyst Fines and Suspended Solids
Fluid Catalytic Cracking (FCC) and hydrocracking units produce catalyst fines that appear in slop oil and process water. These sub-micron particles are difficult to settle, can plug downstream filtration equipment, and contain nickel and vanadium at concentrations that require hazardous waste classification. Effective removal requires coagulation and DAF or disk filtration.
Our Solutions
Tailored Wastewater Treatment Solutions
API and CPI Oil-Water Separation
Gravity-based API separators (per API 421 standard) as primary treatment for free oil removal from refinery and petrochemical wastewater. CPI (Corrugated Plate Interceptor) or TPI units for enhanced oil removal to <50 mg/L before downstream DAF. API separator sizing based on API 421 guidelines — typically surface loading rate 0.3–1.2 m/h, HRT 30–90 minutes for effective free oil removal.
DAF for Emulsified Oil and Suspended Solids
Dissolved Air Flotation (DAF) with coagulant dosing to break oil-water emulsions and remove fine suspended solids including catalyst fines. DAF achieves oil and grease removal to <10 mg/L and TSS <50 mg/L in treated effluent. Essential polishing step between API/CPI gravity separation and biological treatment for reliable performance.
Phenol and Ammonia Stripping
Steam stripping systems for high-phenol and high-ammonia sour water streams — reducing phenol from 100–500 mg/L to <50 mg/L and ammonia from 500+ mg/L to <200 mg/L before biological treatment. Stripped gases (H2S, NH3) routed to sulphur recovery or thermal oxidation. Dedicated SWS unit design and integration with main ETP hydraulic balance.
Biological Treatment with Acclimatised Biomass
Extended aeration activated sludge or MBBR system with biomass specifically acclimatised to petrochemical effluent components — phenol-degrading bacteria, sulphide-tolerant nitrifiers. HRT typically 24–72 hours for complete phenol degradation and nitrification. Anoxic-aerobic staging for combined nitrogen and organic removal. Handles COD 500–3,000 mg/L from pre-treated petrochemical effluent.
Advanced Tertiary Treatment
Activated carbon filtration (GAC contactors, 30–60 minute EBCT) for removal of trace phenols, hydrocarbons, and non-biodegradable COD after biological treatment. Polishing ensures consistent compliance with CPCB phenol <1 mg/L and oil & grease <10 mg/L standards regardless of feed variation. Online effluent monitoring (pH, COD, TSS, oil) integration for OCEMS compliance.
ZLD for Brine and High-TDS Streams
Zero Liquid Discharge systems for high-TDS desalter brine and cooling tower blowdown: pre-treated ETP effluent fed to RO (recovery 60–70%) with pre-treatment to protect membranes from hydrocarbon fouling; RO permeate for reuse in cooling towers or utility applications; RO reject concentrated in MEE or ATFD evaporation systems (operating at 70–85°C, multiple effects) to produce water for reuse and salt/concentrate for disposal.
Technologies
Proven Technologies for Your Industry
Benefits
Why Choose Spans for Your Industry
- Multi-stream design approach — segregating and pre-treating oil, sour water, and high-TDS streams separately
- CPCB Red Category compliance: oil & grease <10 mg/L, phenols <1 mg/L, sulphides <2 mg/L
- API 421-based oil-water separator design for reliable free oil removal
- Acclimatised biological treatment biomass for phenol and hydrocarbon-containing effluent
- Integrated OCEMS monitoring as part of system design
- ZLD-capable design for sites with mandatory ZLD consent conditions
- Hazardous waste stream management and manifest documentation support
- Turnkey project delivery including civil coordination and electrical integration
- Process simulation and mass balance documentation for environmental clearance
- Post-commissioning O&M support with quarterly performance audits
Ready to Transform Your Petrochemical Wastewater Treatment Operations?
Let our experts design a custom solution for your facility.