Under MARPOL Annex IV (Regulation 9) and mandatory IMO Resolution MEPC.227(64), all commercial vessels of 400 GT and upwards or carrying more than 15 persons must operate an approved Sewage Treatment Plant (STP) when discharging treated black and grey wastewater into the sea. Ensuring automated aerobic biological aeration, biomass digestion, suspended solids filtration, and pathogen disinfection prevents severe marine pollution and Port State Control detentions.
Engineering Overview & Table of Contents
- 1. Regulatory Standards: MARPOL Annex IV & IMO MEPC.227(64) Discharge Limits
- 2. Biological Aerobic Digestion: Air Blowers, Diffusers & Biomass Carrier Media
- 3. Membrane Bioreactor (MBR) Filtration: Hollow Fiber Modules & CIP Descaling
- 4. Disinfection Systems: Sodium Hypochlorite Tablet Chlorinators & UV Units
- 5. Certified Effluent Laboratory Testing: TSS, BOD5, COD & Fecal Coliforms
- 6. Statutory Class Certification Across Indian Ports & Shipyards
1. Regulatory Standards: MARPOL Annex IV & IMO MEPC.227(64) Discharge Limits
Under revised MEPC.227(64) standards, treated effluent discharged into international waters must meet stringent criteria: Biochemical Oxygen Demand (BOD5 ≤ 25 mg/l), Chemical Oxygen Demand (COD ≤ 125 mg/l), Total Suspended Solids (TSS ≤ 35 mg/l), Fecal Coliforms (≤ 100 CFU / 100 ml), and pH between 6.0 and 8.5. Seanav delivers certified Sewage Treatment Plant Control Panel servicing, Marine Sewage Treatment Automation Servicing, and effluent water analysis across Hamann, RWO (CleanSewage Bio), Evac (MBR series), ACO Marine (Maripur), and Taiko Kikai suites.
2. Biological Aerobic Digestion: Air Blowers, Diffusers & Biomass Carrier Media
Biological STPs rely on live aerobic bacterial cultures consuming organic sewage waste:
Sewage Treatment Plant Overhaul Protocols:
- Rotary Vane / Side Channel Air Blowers: Overhauling continuous-running aeration blowers; replacing air intake filters, checking relief valves, and lubricating bearings.
- Aeration Fine-Bubble Diffusers: Cleaning EPDM rubber or ceramic membrane diffusers; clearing sludge encrustation ensuring uniform oxygen transfer across bio-chambers.
- Fixed & Moving Bed Biofilm Carriers (MBBR): Inspecting synthetic carrier media surface colonization; purging excess accumulated inorganic sludge to sludge holding tanks.
- Settling Hopper & Sludge Return Airlifts: Clearing airlift recirculating tubes returning settled active biomass back to the aeration tank.
3. Membrane Bioreactor (MBR) Filtration: Hollow Fiber Modules & CIP Descaling
Advanced MBR systems replace gravitational clarifiers with ultra-filtration membrane cassettes (pore size 0.04 to 0.1 microns):
- Chemical In-Place (CIP) Backwash: Circulating sodium hypochlorite and citric acid solutions through membrane fibers to dissolve biological fouling and mineral scale.
- Trans-Membrane Pressure (TMP) Monitoring: Calibrating differential pressure transmitters; verifying automated back-flushing cycles when TMP exceeds 0.35 bar.
- Permeate Extraction Pumps: Overhauling self-priming vacuum extraction pumps and testing non-return check valves.
4. Disinfection Systems: Sodium Hypochlorite Tablet Chlorinators & UV Units
Before discharge overboard, remaining pathogens must be eradicated:
| Disinfection Method | Operating Standard | Seanav Service Scope |
|---|---|---|
| Chlorine Contact Tank | Free chlorine residual < 0.5 mg/l | Servicing calcium hypochlorite tablet eroding feeders; testing de-chlorination dosing pumps. |
| Ultraviolet (UV) Sterilizer | UV dosage ≥ 40 mJ/cm² | Cleaning quartz glass sleeves, replacing UV germicidal lamps, and testing intensity monitors. |
| Discharge Overboard Pump | Automated float switch cut-in/cut-out | Overhauling macerator cutting impellers, motor contactors, and high-level bilge alarms. |
5. Certified Effluent Laboratory Testing: TSS, BOD5, COD & Fecal Coliforms
Port State Control and Class renewal surveys require certified laboratory wastewater analysis. Seanav collects sterile effluent samples dockside, delivering traceable laboratory certificates verifying compliance with MEPC.227(64).
6. Statutory Class Certification Across Indian Ports & Shipyards
Seanav provides turnkey STP overhauls, biological bacterial seed replenishments, air blower replacements, and Class survey testing across Kandla, Mundra, Mumbai, JNPT, Cochin, Chennai, Paradip, and Visakhapatnam.
Schedule Sewage Treatment Plant Survey or Effluent Lab Analysis
Read detailed environmental sanitary procedures on our Marine Environmental & Sanitary Automation Hub or book an engineering visit at any Indian Commercial Port.