Table 1. Produced water characterization in Qatar from the Natural Gas field
[8].
Composition | Concentration Range (mg/L) | References |
Chemical oxygen demand (COD) | 1220–2600 | [4][6][8][26][27] |
Sodium ions (Na+) | 0–150,000 | |
Total suspended solids (TSS) | 1.2–1000 | [4][6][8][19][26][27] |
Calcium ion (Ca2+) | 0–74,000 | |
Total polar compounds | 9.7–600 | [6][8][28] |
Boron (B) | 5–95 | |
Total dissolved solids (TDS) | 100–400,000 | [8][28] |
Chlorine (Cl−) | 0–270,000 | |
BTEX; benzene (B), toluene (T), ethylbenzene (E), and xylenes (X) | 0.73–24.1 | [4][26] |
Magnesium (Mg2+) | 8–6000 | |
Total organic compound (TOC) | 0–1500 | [4][6][19][26][27] |
Iron(II) (Fe2+) | 0.1–1100 | |
Total oil and grease | 2–565 | [28] |
Barium ion (Ba2+) | 0–850 | |
Phenol | 0.009–23 | [6][26][28] |
Potassium ion (K+) | 24–4300 | |
pH | 4.3–10 | [4] |
Strontium ion (Sr+) | 0–6250 | |
Total organic acids | 0.001–10,000 | [4] |
Aluminium (Al3+) | 310–340 | |
Lithium (Li+) | 3–40 | [4][26] |
Lead (Pb) | 0.008–0.08 | |
Bicarbonate (HCO−3) | 0–15,000 | [8] |
Arsenic (As) | 0.002–11 | |
Sulfate (SO2−4) | 0–15,000 | [4][6][8] |
Manganese (Mn) | 0.004–175 | |
Titanium (Ti) | 0.01–0.7 | [4][6] |
Parameter |
Raw Produced Water |
Filtered Water |
Total organic carbon (mg/L) |
389.1 |
317 |
Total nitrogen (mg/L) |
35.77 |
27.6 |
Total phosphorus (μg/L) |
277.78 |
180 |
Benzene (mg/L) |
21 |
16.1 |
Toluene (mg/L) |
3.8 |
3.21 |
Ethylbenzene (mg/L) |
1.22 |
1.05 |
Xylene (mg/L) |
3.43 |
3.11 |
2.2. Characteristics of Produced Water
3.2. Characteristics of Produced Water
Produced water characteristics vary between regions and a specific study for each area should be conducted to investigate the effects of PW discharge on the environment
[8][17][8,18]. Further, PW contains a complex composition of physical and chemical properties, dependent on the geological formation, geographic field
[5], extraction method, and the type of extracted hydrocarbon
[6]. Rahman et al.
[1] detail a list of PW parameters and their typical range. It was observed that the toxicity of the PW generated from gas wells is 10 times greater than the toxicity produced from oil wells
[5]. Given that, special treatment should be taken for PW from oil wells.
The composition of PW from oil fields is summarized in
Table 23. The primary constitutes found in PW are total dissolved solids (TDS), salts, benzene (B), toluene (T), ethylbenzene (E), and xylenes (X) (denoted as BTEX), polyaromatic hydrocarbons (PAHs), oil and grease (O&G). The BTEX are volatile organic compounds that naturally occur in oil and gas wells, including gasoline and natural gas. The BTEX compounds also freely escape into the atmosphere during PW treatment
[25][31]. Additionally, traces of natural organic and inorganic compounds, phenol, organic acids, and chemical additives added during the drilling process can be found in PW and contribute to its total toxicity
[5].
Table 23. Composition of PW from oil and gas field.
Composition of PW from oil and gas field.
Composition | Concentration Range (mg/L) | References |
---|
Table 35. Efficiencies of microalgae in removing organic compounds and nutrients.
Microalgae Species |
Type of Nutrients |
Removal Efficiency% |
References |
Chemical oxygen demand (COD) | 1220–2600 |
Dunaliella salina |
Nitrogen
Phosphorus
heavy metal:
Ni
| [4,6,8,32,33] |
Zn |
65% |
40%
90%
80% |
[40] | [63] |
Sodium ions (Na+ |
Nannochloropsis oculata |
Ammonium and Nitrogen
Organic carbon
Iron |
~100%
40%
>90% |
[41] | [64] |
Parachlorella kessleri |
Benzene and Xylenes
Toluene
Ethylbenzene |
40%
63%
30% |
[42] | [65] |
Chlorella vulgaris | ( | C.v | )
| Neochloris oleoabundans | ( | N.o | ) |
COD by ( | C.v | )
by ( | N.o | )
Ammonia by | C.v. | and | N.o |
Phosphorus by | C.v. | and | N.o |
51%, 55% and 80%
63%, 47% and 72%
(70–84%)
(>84%), (>22%) and (<15%) |
[43] | [66] |
Chlorella pyrenoidosa |
Chromium
Nickel |
11.24%
33.89% |
[44] | [67] |
) | 0–150,000 |
Total suspended solids (TSS) | 1.2–1000 | [4,6,8,20,32,33] |
Calcium ion (Ca2+ |
Table 46. Microalgae cultivation system in different wastewater.
Cultivation System |
Algae Species |
Cultivation Condition |
Type of Waste |
Biomass Productivity g/(L.d). |
Organic Removal |
Biofuel Type |
Refs. |
Total polar compounds |
9.7–600 | [6,8,34] |
Boron (B) | 5–95 |
Total dissolved solids (TDS) | 100–400,000 | [8,34] |
Chlorine (Cl−) |
Closed system (PBRs) |
Scenedesmus acutus (UTEX B72) |
Agriculture-grade urea, triple super phosphate (TSP), pot ash and Sprint 330 (iron chelate) |
Flue gas |
0.15 |
Sulfur, NOx |
|
[45] | [68] |
Closed system 4-L cylindrical photobioreactor (PBR) |
Mixed culture of | Chlorella vulgaris | , | Scenedesmus Obliquus, Botryococcus braunii | , | Botryococcus sudeticus | , and | Afrocarpus falcatus |
pH = 7, Temp = 25 °C. |
|
0.15 |
21, 60, and 47% for protein, carbohydrate and DOC, respectively |
|
[46] | [69] |
500 mL glass flasks |
Dunaliella tertiolecta |
pH—8.1, Temp = 24 °C, f/2 medium |
Real PW |
0.0172 @ salinity 30 gTDS/L to 0.0098 @ 201 gTDS/L |
|
Biodiesel |
[47] | [61] |
500 mL glass flasks |
Cyanobacterium aponinum, Parachlorella kessleri |
pH—8.1, Temp = 24 °C, f/2 medium |
Real PW |
0.113 * |
|
Biodiesel |
[48] | [70] |
|
Synechococcus | sp., | Cyanobacterium aponinum and Phormidium | sp. |
pH = (6–9), |
BG-11 medium |
NA |
|
Biodiesel |
[49] | [71] |
|
Chlorella | sp. and | Scenedesmus | sp. |
pH = 7.1 |
|
0.115 * |
Chlorella | sp.: remove 92% of the TN and 73% of the TOC |
|
[50] | [72] |
|
Dunaliella salina |
Salinity 52.7–63.3 g/L NaCl |
Real produced water |
NA |
Aluminum, barium, copper, magnesium, manganese, nickel, and strontium |
Biodiesel |
[51] | [59] |
Horizontal laminar air flow chamber |
Chlorella pyrenoidosa |
T = 121 °C |
Fogg’s Medium, slant culture |
NA |
|
Biofuel and bioplastic |
| 0–270,000 |
BTEX; benzene (B), toluene (T), ethylbenzene (E), and xylenes (X) | 0.73–24.1 | [4,32] |
Magnesium (Mg2+) |
| 8–6000 |
Total organic compound (TOC) | 0–1500 | [4,6,20,32,33] |
Iron(II) (Fe2+ |
) | 0.1–1100 |
Total oil and grease | 2–565 | [34] |
Barium ion (Ba2+) |
| 0–850 |
Phenol | 0.009–23 | [6,32,34] |
Potassium ion (K+ |
) | 24–4300 |
pH | 4.3–10 | [4] |
Strontium ion ( |
) | 0–6250 |
Total organic acids | 0.001–10,000 | [4] |
Aluminium (Al3+ |
[ |
44 |
] |
[ |
67 |
] |
) | 3–40 | [4,32] |
Lead (Pb) | 0.008–0.08 |
Bicarbonate (HCO−3 |
) | 0–15,000 | [8] |
Arsenic (As) | 0.002–11 |
Sulfate (SO2−4 |
) | 0–15,000 | [4,6,8] |
Manganese (Mn) | 0.004–175 |
Titanium (Ti) | 0.01–0.7 | [4,6] |
Zinc (Zn) | 0.01–35 |
3. Algae-Based Biological Processes
Microalgae are an encouraging technology for the treatment of WW
[29][30][31][32][33][34][47,48,49,50,51,52]. For example, microalgae can uptake different constituents from PW and use them as a growth medium. Given that, algal cultures can solve both economic and environmental concerns and simultaneously produce biomass and other useful chemicals
[35][36][53,54]. Establishing a sustainable green technology such as algae for PW treatment, recovery, and reuse contributes to the production of biomass, which can be converted into biofuel
[30][36][37][38][39][48,54,55,56,57]. This conversion helps to eliminate and save natural gas. Moreover, naturally occurring microorganism seeds in PW can sequentially work with algae and increase the removal efficiency of organic matters and dissolved solids. In sequential processes, algae consume CO
2 and produces O
2, which are essential components for the survival of the microorganism.
Table 35 presents the efficiencies of different microalgae strains and their ability to remove organic compounds and nutrients from wastewater. The removal efficiencies reached up to 50%, 65%, and ≥80% for nitrogen compounds, phosphorous, and heavy metals, respectively. Other constituent (i.e., COD and BETX) removals were related to the strain that was used. Algae-based wastewater treatment can also be performed in different systems as outlined in
Table 46. Depending on the type of system used (i.e., open vs. closed), different removal efficiencies can be achieved.