# Optimizing the Treatment of Produced Water

and Flowback for Reuse or Disposal Brian A. Wrenn PureLine

# Produced Water and Flowback: 

# Characteristics of Concern for Reuse and Disposal

• Dissolved solids  soluble species like sodium, calcium, barium, chloride, sulfate  processes or operations like reverse osmosis, ion exchange, and 

### chemical precipitation are required to remove dissolved solids



## • Suspended solids  particles like sand, metal sulfides, clay, bacteria  suspended solids may be either settleable (e.g., sand) or colloidal 

### (e.g., clay, bacteria)



## • Scale formation potential  Examples: calcium carbonate (calcite), barium sulfate (barite)



## • Iron and manganese

• pH

# Treatment of Produced Water and Flowback by

Coagulation- Flocculation -Sedimentation

• Settleable solids are large enough to be removed from water by 

## settling under the influence of gravity (e.g., sand )

• Colloidal particles are too small to be removed from water by settling under the influence of gravity  colloidal particles can be converted into settleable particles by coagulation and flocculation



## • Coagulation is the process of destabilizing colloidal particles so they can grow into larger, settleable particles  coagulation changes the surface chemistry of colloidal particles in a way that causes them to stick together when two particles collide



## • Flocculation causes colloidal particles to grow into larger, settleable particles  flocculation induces collisions between particlesFe 2+

ClO2 ClO2 - 3 H 2O 3 H +

Fe(OH) 3(s) Step 1: Oxidation of Fe(II) Step 2: Coagulation Step 3: Flocculation 

## Removal of Colloidal Suspended Solids from Produced Water

Step 4: Sedimentation high mixing energyFe 2+

ClO2 ClO2 - 3 H 2O 3 H +

Fe(OH) 3(s) Step 1: Oxidation of Fe(II) Step 2: Coagulation Step 3: Flocculation 

## Removal of Colloidal Suspended Solids from Produced Water

Step 4: Sedimentation moderate mixing energyFe 2+

ClO2 ClO2 - 3 H 2O 3 H +

Fe(OH) 3(s) Step 1: Oxidation of Fe(II) Step 2: Coagulation Step 3: Flocculation 

## Removal of Colloidal Suspended Solids from Produced Water

Step 4: Sedimentation

low mixing energy

## Conventional Process Flow

water coagulant

to filtration Rapid Mix : • high mixing energy
• mix coagulant with raw water

Flocculation : • gentle mixing
• facilitate particle growth through particle- particle collisions

Sedimentation :
• quiescent, uniform, horizontal flow
• particle removal by settling under the influence of gravity

## Oil - Field Implementation of Coagulation - Flocculation -Sedimentation

14 ft10 ft

10 ft 40 ft Floc 1Floc 2

Sedimentation



### Has been used successfully at 7,500 bbl/day ClO2 oil recovery

## Typical Footprint

9

## Coagulation - Flocculation -Sedimentation Bench Tests

before treatment control 35 ppm 80 ppm 150 ppm 230 ppm

beginning of flocculation

settle for 2 hours

## Coagulation - Flocculation -Sedimentation Bench Test Results flocculation sedimentation

### treatment parameter units untreated 230 mg ClO 2

### /liter EC treated sodium mg/liter 35,200 33,200 38,00 potassium mg/liter 422 370 330 calcium mg/liter 4,580 3,940 4,450 magnesium mg/liter 595 520 580 barium mg/liter 

### 15.4 2.6 2.8 strontium mg/liter 

### 1,050 870 1000 iron mg/liter 

### 167 1.0 20 manganese mg/liter 

### 1.1 0.1 1.0 chloride mg/liter 65,260 55,000 68,810 alkalinity mg/liter as CaCO 3 

### 335 118 189 sulfate mg/liter 164 188 340 total sulfides mg/liter 

### 25 0 ND total suspended solids mg/liter 

### 3,960 80 480 turbidity NTU 

### >1100 6 125 pH 6.9 6.5 6.4 density mg/liter 1.07 1.07 1.08 

## Coagulation - Flocculation -Sedimentation Bench Test Results

## Coagulation - Flocculation -Sedimentation Bench Test Results flocculation sedimentation

### treatment

parameter units untreated 40 mg ClO 2

### /liter sodium mg/liter 6,870 7,050 potassium mg/liter 5.8 5.8 calcium mg/liter 74.7 74.1 magnesium mg/liter 15.1 14.8 barium mg/liter 16.2 15.1 strontium mg/liter 3.0 3.0 iron mg/liter 

### 42.7 1.2 manganese mg/liter 

### 0.5 0.2 chloride mg/liter 9,910 9,760 alkalinity mg/liter as CaCO 3 1,100 1,080 sulfate mg/liter 2.3 0.0 total suspended solids mg/liter 

### 160 10 turbidity NTU 

### 177 8 pH 8.1 8.1 density mg/liter 1.01 1.01 

## Coagulation - Flocculation -Sedimentation Bench Test Results

## Coagulation - Flocculation -Sedimentation Bench Test Results

before treatment control 0 ppm 10 ppm 20 ppm 80 ppm

end of flocculation

settle for 2 hours 40 ppm

## Coagulation - Flocculation -Sedimentation Bench Test Results

### treatment

parameter units no ClO 2 

### 20 mg ClO 2

### /liter sodium mg/liter 74,000 68,600 potassium mg/liter 5,480 5,570 calcium mg/liter 17,100 17,000 magnesium mg/liter 1,430 1,430 barium mg/liter 11.6 11.5 strontium mg/liter 1,500 1,450 iron mg/liter 

### 24.7 2.5 manganese mg/liter 16.5 15.8 chloride mg/liter 162,000 165,000 alkalinity mg/liter as CaCO 3 413 402 sulfate mg/liter 325 310 total suspended solids mg/liter 

### 1,110 164 turbidity NTU 

### 240 45 pH 6.9 6.9 density mg/liter 1.20 1.20 

## Coagulation - Flocculation -Sedimentation Bench Test Results

# Conclusions

• Chlorine dioxide is an effective coagulant for removal of suspended solids from produced water and flowback  ClO2 

### oxidizes dissolved iron (Fe 2+

### ) to form solid Fe(OH) 3 

### , which 

### acts as coagulant  turbidities <10 NTU and suspended solids concentrations <20 mg/liter are achievable



## • Treatment with chlorine dioxide will oxidize iron, sulfides (in any form), and kill any bacteria that are present

• Flocculation and sedimentation can remove important scale species, such as barite and calcite  this process can be modified to remove scale-causing compounds (e.g., calcium, barium, bicarbonate) that are not present above the saturation limit in the raw water

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