You can try a super-pulsator clarifier. See link: http://www.degremont-technologies.com/IMG/pdf/tech_infilco_TEXAS.pdf. 

You may can try to use spectrophotometric instrument to find the most sensitive wavelength (that can reach your detection limitation range), which can make a standard curve of the correlation between turbidity and absorbance. My experience is the standard curve should be fit very well under a specific test range. Thanks

It depends on how much money you want to apply to the treatment and how many cubic meters per second of treated water. You can use molecular membrane system (from ultrafiltration to reverse osmosis)

Sand filtration may also be a low-cost alternative to membrane separations, if  you are only interested in removing suspended solids from the water stream.

DEPENDE EL VOLUMEN DE AGUA: PARA GRANDES VOLÚMENES LO MAS ECONOMICO ES FILTRACIÓN POR LECHO DE ARENA. PARA VOLUMENES PEQUEÑOS RECOMIENDO LECHO DE DIATOMEAS.

EN VOLUMENES PEQUEÑOS DE AGUA DE MAR (ACUARIOS DE EXHIBICION DE MAS DE 5OO LITROS) LOS MOLUSCOS BIVALVOS (COMO Mytillus sp. EN AGUAS TEMPLADO FRIAS) SON EXCELENTES !!!

Hello, Dear Mostafa

You can use the mud or mix of clay and Seashells (crushed Seashells look like  powder )in order to provide synthetically high turbidity and make a initially core for forming sludge , so you can add it  to water.  

I would also recommend filtration, although it depends on whether the water is always of low turbidity or it changes with time in which case filtration alone will not be a good idea when turbidity is high.

All the best

YOU COULD TRY SEQUENCING BATCH MEMBRANE REACTOR

Pocos investigadores tienen en cuenta la relación costo/beneficio y el volumen a filtrar. 

To decrease the turbidity in low cost sand filter and if there chose for high tech MBR is the offer and before sedimentation is recommended.

I would also vote for slow sand filtration. It is simple because it can provide a single-stage treatment for raw water with low turbidity value. Its simplicity leads into low capital cost as well for operation and maintenance cost. Additionaly, slow sand filtration can improve the biological quality of the filtrate especially when the media has reached its maturity.

The best alternative, except for slow sand filtration, is two-stage filtration. Read Kawamura's articles on this subject.