Utilizing RO Brine Water in Rapid Sand Filters Backwashing

By Green Path Solutions Al Obeid, Mohammad Faris Water & Energy Consultant Mar, 2019

1 Introduction: Water position in the region is becoming a very hot topic due to scarcity as a result of very limited resources.

The situation is becoming more worse and worse specially in Jordan due to the pressure of the refugee coming from the neighboring countries which exceeding the capacity of the existing resources.

So increasing the efficiency of system will contribute in decreasing the deficit between water demand and supply.

2 Abstract: This presentation shows the feasibility of using the brine water of brackish systems in backwashing the multimedia sand filters vessels instead of using the normal conventional filtrated water.

The initiative is proven to have the same or higher cleaning effect than the conventional way without any negative impact in the filter media or any observation of salt precipitation.

The system was validated on two plants with 400 & 600 m3/h for a period of more than 15 & 10 years respectively, it had a successful outcomes.

3 Scope: Using rapid pressurized sand filters in closed system with brackish water that is highly polluted with:

• Total Dissolved Solid , TDS=18,000mg/l • Suspended solids. • . • High content of inorganic compounds, i.e. Iron = 5.0mg/l

4 Project Description: Eliminate the volume of raw water used for the sand filters backwashing process by using RO brine water for this process, then send it direct to the final drain or evaporation bond.

The rinsing process will use a small amount of raw water for the flush the filter media and remove any traces of high saline water may remain from the backwash process.

5 System Overview: The typical brackish water treatment system usually consists of:

• Water resource: surface or ground water. • Pre-treatment process: Oxidation, sedimentation, , cooling,... • Desalination process: RO unit. • Post-treatment process: PH adjustment, disinfection…

The water losses occur through pre-treatment & RO processes.

6 Fact Figures: Due to highly contaminated water with suspended solid and iron content, the pressurized need at least twice a day of complete backwash cycle.

Typical figures are shown 5% of the total plant feed water consumed during sand filter backwash process, while 15% drained out from the RO desalination units as brine water.

Our experiment is based on how to eliminate the losses during the backwash process.

7 Method: The steps below show how to perform backwashing by the RO brine water:

• Collect the RO brine water in a break tank. • Drain the sand filters from the filtered water to the RO feed tanks before starting the backwashing cycle. • Use the RO brine water as a source for sand filters backwashing. • Before rinsing, drain the sand filter from the brine water to the final drain. • Rinse the sand filter by the feed water then send it to the RO feed tank. • Measure the TDS of the rinsing water to ensure that it will not impact the quality of the RO feed water.

8 Process configuration: The diagram below illustrates the modified configuration of the water treatment system:

9 Sand filter new configuration: The below pictures show the proposed pipes configuration of the sand filter to use the RO brine water for filter backwashing process:

10 Investment: The below investments are required to perform this task :

• A break tank for brine water collection. • Pumping system to perform the backwash process. • Slight modification in sand filters vessel's face piping.

In my case The investment cost of modification was returned back with less than 12 months.

11 Results: The below are the achievements after using the RO brine water for sand filters backwash:

• Increase the WTP overall productivity by 5%. i.e increase the raw water utilization by 5%. • Reduction of 100% in filtrated water used during backwash. • Increase the performance of the sand filters.

12 RO Brine water in SF backwash

PROS CONS

Special type of coating & modification in sand 1 Low SDI & high buffering capacity filter

2 Saving in water consumption ratio Rm3/Pm3 Separate pump & break tank for brine water

Saving in the cost required to increase the Drain all the brine water inside the filter at the 3 quality of raw water required to backwash the end of backwash before start rinsing. filters.

13 Conclusion: The Brackish RO brine water can be used for rapid sand filter backwashing before dumping it to drain without any negative impact in filtration or RO processes.

In contrary the brine water proves that the filtration performance was improved.

While the most important thing is the reduction of the quantity of water consumed through the water treatment system, i,.e elimination all the water losses prior to the RO process mainly in filter media backwashing.

14 Q & A By Green Path Solutions Al Obeid, Mohammad Faris [email protected] +962 79 299 1860 Water & Energy Consultant Mar, 2019

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