In many standard: 5 NTU

Dear Dr Ashwani

You are absolutely write, It was a typing mistake, Please forgive me. I did correct the unit.

Regards

it is 5 NTU in many standards

Salam

Based on appearance, turbidity should not exceed 5 NTU. If bacterial disinfection is in place, then a turbidity of less than 1 NTU at the time of treatment is desirable.

In general, Desirable limit: 5 NTU and Permissible limit: 10 NTU.

Regards

Dr. Raza

The answer to your question depends on the type of water you are treating; consequently, in the U.S.A turbidity is regulated as a "treatment technique", and depends on whether you are treating surface water, groundwater under the direct influence of surface water, or groundwater. Additionally, the turbidity level is further regulated within each classification of water by the type of treatment one has implemented. The type of treatment may also be regulated in and of itself. EPA's health effects language that explains the maximum contaminant level designation for turbidity states that higher turbidity levels are often associated with higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria. These organisms can cause symptoms such as nausea, cramps, diarrhea, and associated headaches.

Surface Water Treatment Rule requirements: EPA’s surface water treatment rules require systems using surface water or GWUDI to (1) disinfect their water, and (2) filter their water or meet criteria for avoiding filtration so that: (i) Surface water systems and GWUDI systems that use conventional and direct filtration: (ii) At no time can turbidity (cloudiness of water) be higher than 1.0 nephelometric turbidity unit (NTU); samples for turbidity must be less than 0.3 NTU in at least 95 percent of samples in any month. (iii) Surface water systems and GWUDI that use slow sand filtration or diatomaceous earth filtration: samples for turbidity must be less than 1 NTU in at least 95 percent of samples in any month.

Surface water systems and GWUDI that use alternative filtration (technologies for filtering other than conventional, direct, slow sand, and diatomaceous earth filtration): Follow state limits, which should be at least as stringent as the following: Turbidity must not exceed 5 NTU; samples for turbidity must be less than 0.5 NTU in at least 95 percent of samples in any month.

These standards, in combination with disinfection, must ensure that the system reliably achieves required pathogen control on a continuing basis.

As write Steven, the best is that the turbidity  not exceed 5 NTU in any sample; samples for turbidity must be less than 0.5 NTU in at least 95 percent of samples in any month.These standards, in combination with disinfection, must ensure  the desinfection efficiency

Accordant to EPA National  Drinking Water Standards, in filtration system, the turbidity should not be higher than 1 NTU (0.5 NTU for conventional or direct filtration) in at least 95% of the daily samples in any month.

In some water treatment plants such as (Majmaah City, KSA), turbidity produced after R.O was 0.01 NTU.

Hi

In Tehran water treatment plant we set this parameter to 0.5-1 NTU , But most of the time was 0.5 NTU.

I know that level of turbidity until 5 NTU is acceptable, but in my perspective and experience lower NTU level effectively have much better quality.

best regards. 

As per IS 10500:2012 (Indian Standard) max. acceptable limit of turbidity is basically 1 NTU and permissible limit in absence of alternative source is 5 NTU.

As per Indian Standard, turbidity should not be more than 5 NTU

less than 5 NTU

Hello Dr Sameh S Ahemd

The WHO (World Health Organization), establishes that the turbidity of drinking water shouldn't be more than 5 NTU, and should ideally be below 1 NTU.

The European standards for turbidity state that it must be no more than 4 NTU.