# Optimizing the Treatment of Produced Water and Flowback for Reuse or Disposal

Brian A. Wrenn PureLine

## • Chemistry

– ClO 2 

### is an effective oxidant and biocide

– treats H 2 

### S, iron, FeS , SRB, APB, and other contaminants of
concern

– pH independent: effective over a broad range

– environmentally friendly: EPA and FDA approved



## • Experience

– 134 years collective technical experience

– scientists, engineers, applications specialists



## • Equipment

– mobile units generate ClO 2 

### on demand for on-the-fly treatment



## • Control

– PureLine ClO 2 

### generators adjust dose automatically

... no more over treating! 

# Why Consider PureLine ?

# Mobile Unit On-Site Today

## 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

• 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+ ClO 2 ClO 2 -

3 H 2 O 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: SedimentationFe 2+ ClO 2 ClO 2 -

3 H 2 O 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+ ClO 2 ClO 2 -

3 H 2 O 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+ ClO 2 ClO 2 -

3 H 2 O 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 ft 10 ft

10 ft 40 ft ClO 2

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

14 ft 10 ft

10 ft 40 ft

Floc 1 Floc 2

ClO 2

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

14 ft 10 ft

10 ft 40 ft

Floc 1 Floc 2

Sedimentation



### Designed to treat 5,000 bbl /day ClO 2 oil recovery

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

14 ft 10 ft

10 ft 40 ft

Floc 1 Floc 2

Sedimentation



### Has been used successfully at 7,500 bbl /day ClO 2 oil recovery

### Typical Footprint

15

### 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 Results21 

### 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 ppm22 

### Coagulation-Flocculation-Sedimentation Bench Test Results

## Conclusions

• Chlorine dioxide is an effective coagulant for removal of suspended solids from produced water and flowback
! ClO 2 

### 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