## 2 Wastewater Treatment by Microalgae
### Industrial Wastewater  
#### 2.3.1 Physicochemical Properties  
Industrial wastewater could come from a wide range of industries (Figure 5), such as the textile and food processing industries (sugar, starch, vegetable oil, shortening, potato, dairy, fruit juice and beverage, brewery and distillery industries) [88; 89] and is one of the most significant pollution sources in the environment and has different properties.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Algae Used** & **Wastewater Type** & \begin{tabular}{c} **Growth Rate or** \\ **Volumetric** \\ **Productivity** \\ \end{tabular} & \begin{tabular}{c} **Final Biomass** \\ **Concentration** \\ \end{tabular} & \
\begin{tabular}{c} **Production of Target** \\ **Metabolites** \\ \end{tabular} &
\begin{tabular}{c} **References** \\ **References** \\ \end{tabular} \\ \hline _Acutodesmins obliquus_ & Pigery & 1850 mg-cell L\({}^{-1}\) d\({}^{-1}\) & nr & nr & [66] \\ _Arthospira maxima_ & 10\% Neisayote & 0.27 d\({}^{-1}\) & 32 \(\times\) 10\({}^{4}\) cell mL\({}^{-1}\) & nr & [62] \\ _Arthospira platensis_ & Dairy farm & 0.50 g L\({}^{-1}\) d\({}^{-1}\) & 4.98 g L\({}^{-1}\) & Lipids: 30.23\% & [72] \\ _Botryococcus Brunnii_ & Aerated swine & nr & 0.94 mg L\({}^{-1}\) & Hydrocarbon: 23.8\% & [74] \\ _Chlamydomonas_ sp. & Swine & 49.70 g m\({}^{-2}\) d\({}^{-1}\) & 37.73 mg L\({}^{-1}\) & Lipids: 17.67\% Protein: & [61] \\  & & & & 33.94\% & \\  & & & & Chlorophyll: 15.57 mg L\({}^{-1}\) & \\ _Chlorella pyreneoulosa_ & Paddy-soaked & 0.42 d\({}^{-1}\) & 1.56 g L\({}^{-1}\) & Lipids: 27.47\% & [76] \\  & & & & Carbohydures: 23.77\% & \\  & & & & Proteins: 46.12\% & \\  & & & & Proteins: 57.30\% & \\  & & & & Extracellular & \\  & & & & polysaccharides: 14.87\% & [59] \\  & Digested swine & & & Crude fibre: 3.08\% & \\  & & & & Crude ash: 5.57\% & \\  & & & & Lipids: 6.3 mg L\({}^{-1}\) d\({}^{-1}\) & [68] \\ _Chlorella sonkiniama_ & & & & Lipids: 6.27 mg L\({}^{-1}\) d\({}^{-1}\) & [58] \\  & & & & \\  & & & & & \\  & & & & & \\  & &  
Different techniques have been used to treat this type of wastewater, among them is the treatment by microalgae [90]. Table 9 summarizes the properties of different industrial wastewaters which have been treated using microalgae, food-processing wastewater being the most investigated wastewater in the literature. This type of wastewater often has a high chemical oxygen demand and high total nitrate and total phosphate concentrations levels [5], for example, an olive oil mill wastewater contains 56,740-124,600 mg L\({}^{-1}\) of COD, 130-190 mg L\({}^{-1}\) of TN and 350 mg L\({}^{-1}\) of TP, as well as soybean wastewater which has 5320-22,700 mg L\({}^{-1}\) of COD, 267.1-950 mg L\({}^{-1}\) of TN and 23.28-56.3 mg L\({}^{-1}\) of TP [91, 92, 93, 94, 95, 96]. Winery wastewater has a high COD content (119,300 mg L\({}^{-1}\)) and a lower TN (12.14 mg L\({}^{-1}\)) and TP content (3.46 mg L\({}^{-1}\)) [70]. On the other hand, textile wastewater is characterized by a high concentration of the total suspended and dissolved solids, chemical oxygen demand and a strong color [5, 97]. As reported in Table 9, it contains 1050 mg L\({}^{-1}\) of TSS, 1378.2-4458 mg L\({}^{-1}\) of COD and 43.57 NTU, which is lower than a palm oil mill effluent (244 NTU) [98, 99].  
Chemical industry wastewater, such as that from pesticides and pharmaceutical processing industries, used in the literature as culture mediums for microalgae, contains high total organic carbon (TOC) and low total nitrate (TN) and total phosphate (TP) concentrations, with 7185.93 and 480.93 mg L\({}^{-1}\) of TOC, 0.02 and 0.23 mg L\({}^{-1}\) of TN and 1.01 and 0.52 mg L\({}^{-1}\) of TP, for pharmaceutical and pesticide processing wastewaters, respectively [32].  
Figure 5: Industrial wastewater types.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline
**Type** & **pH** & **TSS** & **TOC** & **COD** & **NO-N** & **NO-N** & **NH-N** & **NH-N** & **PO-P** & **TN** & **TP** \\  & **(mg L\({}^{-1}\))** & **(mg L\({}^{-1}\))** & **(mg L\({}^{-1}\))**