Sewage Treatment Plant maintenance:

.Sewage Treatment Plant maintenance

.stp .stpm .stp maintenance

Regular maintenance is required

• to ensure biological treatment process is running smoothly
• Ensure there is no formation of methane gas and toxic fumes from anaerobic process.
• Bacteria must be kept alive by maintaining the correct conditions as they are very sensitive to temperature, type of water and regularity of flow. Oil or grease coming to the plant can kill the bacteria.
• Metallic object, rubber goods and absorbent cotton must not be disposed into the sanitary system.
• Chlorine tablet regularly adding, compressor filter cleaning, greasing, system flushing must be done regularly

Daily

> Check for any abnormal alarms

> Check smell and abnormal noise from blower and pump

> Check the sludge return flow from settling tank to aeration chamber

> Check the chemical dosing tank

Weekly

> Take a sludge content test

> check chlorine content of effluent

Monthly

> Check aeration lines are clear. If solenoid valves are present check the working of the

same.

> Do backwash if the sludge content is high

> Check that there is no obstruction in the venting line

> Inspect the tank’s external and internal coatings for corrosion

> Try out all the external valves

> Try out high level alarms

Yearly

> Empty whole system and clean thoroughly

> Clean the floats for pump cut in and cut of as well as high level alarm

> Replace the gaskets if required

> Replace the non return valve in case of vacuum STP

Use several litters of lime removing agent at each end of vacuum line then flush the toilets every two weeks

Sewage Waste:

The Sewage waste produced on the ship can further be divided into two categories; Blackwater and Grey Water. Together they are called as wastewater.

Black Water Waste

Black water waste on ships consists of three main categories:

1. Toilet and Urinal Waste: This includes all drainage and waste from toilets and urinals.
2. Medical Area Waste: This encompasses waste from medical facilities like dispensaries and sickbays, including drainage from wash basins, wash tubs, and scuppers in these areas.
3. Cargo Hold Drainage: This involves drainage from cargo holds containing living animals, as well as other wastewaters mixed with such drainage.

Grey Water Waste

Grey water waste on ships is divided into five categories:

1. Galley Waste: This includes drainage from dishwashers and washbasins in the galley (ship’s kitchen).
2. Personal Hygiene Waste: This comprises drainage from cabin showers, baths, and washbasin drains.
3. Laundry Waste: This is the waste generated from laundry drainage.
4. Deck Drainage: This refers to wastewater from interior deck drains.
5. Condensate: This includes condensate from refrigerators and air conditioners.

What PSC inspect in sewage system?

.sewage psc .psc sewage

PSC Inspections of Sewage Systems

PSC inspectors may check:

1. Proper operation of sewage treatment plant (STP) by crew
2. Crew knowledge of regulations
3. Sewage discharge valve closed/sealed in port
4. Condition of STP internal chamber
5. Safety management system includes STP maintenance procedures
6. Chlorine content of effluent
7. Logs of discharge valve operation
8. Validity of International Sewage Pollution Prevention Certificate

Sewage Effluent Tests

Key tests conducted onboard:

• Chlorine test (≤5 ppm in chlorine contacts compartment)
• Suspended solids
• Biochemical oxygen demand (BOD)
• Coliform count
• Chemical oxygen demand (COD)

Suspended Solids Test

• Collects and weighs solid material in effluent
• Uses asbestos mat filter
• Results in ppm or mg/L

BOD Test

• Incubates 1L sample at 20°C in oxygenated water
• Measures oxygen consumed
• Results in mg/L or ppm

Coliform Count

• Indicates effectiveness of disinfection
• Counts coliforms per 100 mL of effluent
• Incubated for 48 hours at 35°C

Permissible Discharge Limits (MEPC.227(64))

• Suspended solids: 35 mg/L
• BOD: 25 mg/L
• E. coli count: 100/100 mL
• COD: 125 mg/L

These tests and limits help ensure proper sewage treatment before discharge to protect marine environments.

MEPC 227(64) – Sewage Effluent Standard:

.mepc227 .mepc 227(64) .mepc22764

Resolution MEPC.227(64) Summary

Resolution MEPC.227(64) outlines the 2012 Guidelines on Implementation of Effluent Standards and Performance Tests for Sewage Treatment Plants adopted by the Marine Environment Protection Committee (MEPC) on October 5, 2012. Key points include:

1. Purpose and Application

• Updates previous guidelines (MEPC.159(55)) to reflect current trends and advancements
• Applies to sewage treatment plants installed on or after January 1, 2016, on various ship types and areas

2. Technical Specifications

General Requirements:

Sewage treatment plants must meet specific effluent standards without relying solely on dilution.

Effluent Standards:

• Thermotolerant Coliforms: Not to exceed 100 thermotolerant coliforms/100 ml
• Total Suspended Solids (TSS): Not to exceed 35 Qi/Qe mg/l
• Biochemical Oxygen Demand (BOD5) without Nitrification: Not to exceed 25 Qi/Qe mg/l
• Chemical Oxygen Demand (COD): Not to exceed 125 Qi/Qe mg/l
• pH: Between 6 and 8.5

Additional Standards for Passenger Ships in Special Areas:

• Nitrogen and Phosphorus Removal: Specific limits for total nitrogen and phosphorus

3. Testing Considerations

• Raw Sewage Quality: Fresh sewage with appropriate total suspended solids concentration
• Duration and Timing: At least 10 days, capturing normal operational conditions
• Loading Factors: Testing under minimum, average, and maximum volumetric loadings
• Sampling Methods and Frequency: Representative sampling with at least 40 effluent samples
• Analytical Testing: Specific methods recommended for testing effluent parameters

4. Certification

• Certificate of Type Approval: Issued by the Administration after satisfactory testing
• Form of Certificate: Includes details of the sewage treatment plant, test results, and operational conditions

5. Renewal and Additional Surveys

Administrations should ensure continued performance in accordance with MARPOL Annex IV.

6. Familiarization and Maintenance

• Ship personnel should be familiarized with operation and maintenance
• Routine maintenance should be clearly defined and recorded

These guidelines provide a uniform interpretation of MARPOL Annex IV requirements and assist in determining appropriate parameters for sewage treatment plants.