Handling and Disposing of Greywater

Greywater is kept separate from sewage, or blackwater, because it may be disposed of in different ways, depending on where the shipyard is located and what local legislation is in effect.

Work Preparation

When working with greywater it is important to think about the steps that need to be taken prior to beginning the work. 

Before working with greywater pipes or tanks:

  1. The system must first be locked out or de-energized if it is still hooked into the ship's power.
  2. Personnel onboard the ship should be notified when the greywater system should not be used.
  3. Workers going into the areas must be wearing suitable Personal Protective Equipment (PPE).   PPE will include disposable coveralls (over regular coveralls), safety glasses, and/or face shields, gloves and steel toed rubber boots.  Many workers may also wear respirators when working with greywater to avoid inhaling air-borne contaminants.
  4. Personnel working with greywater should be vaccinated against hepatitis. 
  5. The work areas should be cordoned off with barrier tape to ensure other workers are aware of the potential hazards.
  6. Depending on the condition of the water, temporary ventilation may be required to remove offensive or harmful fumes once the system is opened.
  7. In severe cases, safety personnel may need to verify the oxygen content in a tank or compartment before work begins.  

 Pumping out the Tank

Large discharge pumping lines are used to remove greywater from a ship under the following circumstances: 

  1. When holding tanks are to be emptied ashore into a treatment plant;
  2. If an onboard treatment or pumping system has failed and needs to be opened,
  3. If a tank is being cleaned out.

If lines are being hooked up to a tank discharge valve, a bucket or some other type of containment may be put below the valve to catch spills. If the suction line is to be put directly into a tank to suck out the liquid, the tank lid must be removed carefully and wiped down to prevent liquid or sludge from contaminating the worksite. The line will be placed into the tank and usually tied off/secured to prevent it from inadvertently being removed.

Once the pumping begins, the tank is monitored to ensure the line is operating correctly. It will usually have a large bulbous screen on the end to prevent the ingress of large objects that might stop the suction or cause the hose end to stick directly to the tank bottom.

Another person should be located at the pump end and in radio contact in case the pump needs to be shut down if any problems arise. If a tank is simply being pumped down to empty it, the tank can be flushed with fresh water before being closed up. The hose will also have been flushed out (with the pump running) to remove the majority of contaminants.

Once the pump is shut down, the hose end will be bagged or wrapped and then removed. The tank lid gasket should be checked and if damaged it will be replaced before fastening the lid back down. If the pump line was hooked directly to a valve, the tank will be flushed with clean water and then the valve will be shut and wiped clean. All contaminated rags will be disposed of ashore. The pump suction lines or hoses will be rolled up and carefully removed from the ship to avoid contaminating any other work areas.

The same care during cleanup must be taken when sections of line, cleanouts, traps, or other parts of the piping or collection system need to be worked on anywhere else on the ship. If further work is required on the system, like power tooling the inside surface of the tank, or re-coating it, the entire surface will first be steam cleaned to remove all possible surface contamination and then usually wiped down with rags. The suction line is again used to remove all liquids and the rags will be disposed of in an appropriate manner.

Hoses are carefully removed from the ship and before being stored, they are usually steam cleaned. Tools should be wiped down, cleaned, and properly disinfected to prevent any problems. The fluid collected in the "shore" tank on the jetty must be disposed of as defined by municipal guidelines and rules.