Water Treatment Systems

Following the environmental European regulation, bilge waters, hull’s wash waters and also all the rain waters falling on the yard must be collected and treated before sending to sewers, sea, lakes or rivers. All the mentioned waters may contain contaminants like: oil, emulsified oil, hydrocarbons, emulsified hydrocarbons, acids, solids, suspended solids, heavy metals, soap, grease and others. The easiest way to separate oils and Hydrocarbons from water is to use an OIL SEPARATOR. And the easiest way to separate solids (also in small dimension is to use a SEDIMENTATION TANK. It is also possible to have only one tank with oil separator and a sedimentation chamber. Unfortunately with these two processes is impossible to remove emulsified oil and hydrocarbons, acids and heavy metals. Moreover if we want to have a good sedimentation process we must wait a very long time (few days). The only available system to remove in a very short time all those contaminants is the FLOCCULATION chemical process. The flocculation chemical process consist in mixing the waste waters with a chemical called ANIONIC POLYELECTROLITE.

This chemical helps the molecules of similar material and dimension to join together in bigger particles that, having a higher weight will precipitate in a shorter period.

But the flocculation chemical process is possible only if the water is neither too acidic or alkaline. Therefore to be sure that the flocculation process can work properly is necessary to add a second chemical able to adjust the Ph of the water. This chemical is the sodium hydroxide. Another way to solve the Ph problem is to add, instead of the sodium Hydroxide, another coagulant with different able to make flocculation in a wider range of Ph. This chemical is ferric Chloride and the Ph range is from 4 to 11. Generally the flocculation chemical process is well known as CHEMICAL – PHYSICAL PROCESS while the chemicals anionic polyelectrolyte and ferric chloride are well known as PAC and PAM. These two chemicals are widely used on the market and can be found in powder or in liquid form. The last method to treat the shipyards and marinas waste water is MECHANICAL PROCESS. It is possible, using a high pressure pump to filter the water through two different material able to retain the impurities. These material are the quartz sand (bigger particles) ad activated carbon media filter (smaller particles). Shipyard Solution technology adopt (for the bigger systems) a water treatment process where all the mentioned technologies are used to ensure a very high quality of the treated waters. More specifically in WT002 or bigger models will find the following flow diagram:



With many years experience in shipyards and marinas waste water treatment, Shipyard Solution is confident that this process is very good and also very stable. In case of high picks of certain contaminant like oil, hydrocarbons or acids, the quality of the treated waters will be always stable. The oil separator will dilute any hydrocarbons or oil picks while the quarts and activated carbon media filter are used as a security additional process in case of high picks of acids in the waste waters. The result of the water treatment is the following: the first sample (on the left) is a bilge waste water sample before the treatment; the second sample is a sample taken from the system just after the mixing chamber (beginning of flocculation); the third sample is a sample taken from the sedimentation chamber; the last tree samples are treated water samples taken from the system after 1 hour, 3 hours and 6 hours of continuous running of the system.

Shipyard Solution product range is very wide and include system with a flow rate from 0,5 m³/h to 30 m³/h. Such a wide range of flow rates is needed because shipyards and marinas don ‘t need to treat only the bilge waters and the hull’s wash waters. They need to treat also the rain waters falling on all the areas of the yard. Consequentially, much big is the shipyard, much big will be the volume of waters to be treated. The EU regulation state that the shipyard has 48 hours from the end of the rain event to treat the rain waters. On the other hand, the same regulation state that is necessary to treat only the first 5 mm of rain falling on the yard. The regulation state also that the first 5 mm of rain are enough to remove from the ground all the pollutants and that all the waters falling thereinafter can be sent to sewer, sea, lakes or rivers directly. Therefore is needed to make a proper calculation to understand which is the needed flow rate for each shipyard and it is also absolutely important to explain the shipyard how to make the right collecting tank.
First of all the shipyard MUST have a proper grids system able to collect all the yard’s rain waters in a collecting tank before treatment. The collecting tank must have the function to collect only the first 5mm of waters.

The collecting tank will collect all the waters: rain waters and hull’s wash waters. The function:

Rain waste water function:
The function is activated with the Plant in OFF mode

Rain waters must be collected via one or more grids and enter the first small tank. The waters will flow in the first section of the big tank. The septum (sedimentator) between the first and second part of the big tank will not allow any solid to pass near the submerged pump.
The solids will then remain in the first section. When the first sector will be full the water will overflow in the second part of the collecting tank. This part of the collecting tank must CONTAIN THE 5 MM OF RAIN WATERS. To calculate how big must be this part of the tank it’s needed to know the total m² of the yard.
Let’s imagine, as a mere example:
Yard is 1.000 m²
We must collect 5 mm X 1.000 m² = 5.000 mm³
5.000 mm³ = 5 m³

Therefore the second part of the collecting tank must have a capacity of 5 m³ (from the bottom of the tank to the overflow pipe). If the rain event will continue after the collection of the first 5 mm of waters, the second section of the collecting tank will be full, the first section of the collecting tank will be full. Therefore the level of the water in the first small tank and the waters exceeding the first 5 mm will be sent directly to sewer, sea, lakes or rivers. At the end of the rain it will be possible to switch the system from OFF to ON and the plant will automatically treat all the waters contained in the collecting tank. When the collecting tank will be empty, the level meter will automatically switch OFF the plant.

Hull’s waste water function:
The function is activated with the Plant in ON mode

Rain waters must be collected via one or more grids and enter the first small tank. The waters will flow in the first section of the big tank. The septum (sedimentator) between the first and second part of the big tank will not allow any solid to pass near the submerged pump.
The solids will then remain in the first section. When the first sector will be full the water will overflow in the second part of the collecting tank. The level meter will activate the submerged pump when the water level will reach the desired level and the plant will automatically treat the waters.

The water treatment plants have a production of MUD. The Mud must be collected, dried and sent to authorized companies for disposal.