The company who provides environmental
protection service may have the business for dredging in rivers or lakes. Many
years’ soil sedimentation down to the water bottom, leaves falling into the
water and then rot, and the trash threw into the water will make the river bed
higher and higher which leading the pollution of the water and even the cutoff
of the river flow. Therefore, we need find a solution to take out the sand,
silt and trash at the bottom of water to make the water clean.

To take the solid stuff out from the water,
we need a solid and liquid separation system to do this job. As a leading
manufacturer of solids control equipment, GN solids control luckily
jointed a project to make the lake water clean inside a residence district.
There is a dredging boat that can take the solid mixed with water from bottom
of the lake, the dirty slurry was sucked out and delivered on to the land with
smelly smell.

The slurry is fed via a steel wire box
where large size solid stuff will be blocked and collected. Then the liquid
will be pumped to GN’s solids control system. In this system, GN designed 3
stages for solids control including shale shaker,
de-sander and de-silter. Both the de-sander and
de-silter are equipped with underflow shaker that could make the discharges
from cyclone much dryer. After treated by the de-silter cyclones, the solid
stuff with size larger than 15-20 microns will be removed. And the rest solid
in the slurry is difficult to remove by using mechanical machinery.

Flocculation is a good method to gather the
ultra fine solids in the slurry. Add the flocculation agent into the slurry as
per certain ratio and then fully mix with mud agitators. The
flocculated slurry will need several times for sedimentation and then will be
pumped to belt filter press for final dewatering process. The solids will be
discharged with a thin cake shape, and the water could be discharged directly
back to later or river.  

The advantage of the filter press is to
make the solids much dryer, and disadvantage is high cost and small treating
capacity. Some other contractor will use decanter centrifuge to do the final
dewatering job on consideration of its larger treating capacity.