**2. Materials and methods**

#### **2.1 Study area**

The Gomti River is one of the major tributaries of the Ganga, situated 26.8°N, 80.9°E in Lucknow city after 250 km flowing river from the origin point. The river

#### *Promising Techniques for Wastewater Treatment and Water Quality Assessment*


#### **Table 2.**

*Description and geographical position of sampling sites in the Gomti River.*

serves as one of the major source of drinking water for the Lucknow city and the population of about more than 4.5 million helped by the river in a different way. The study area covers 10 different locations presented in **Table 2**. In this study, selected total 10 reasonable locations in the Lucknow city being an over loaded of pollutants source in stream and identified the levels of toxic heavy metals and other characteristics.

#### **2.2 Criteria for the river water sampling**

Sampling stations were selected considering the population load, demographical distribution of river and sources of wastewater. One of the main goals of this study is to collect the samples that are representative of the site conditions, so that an accurate assessment can be made with a minimum number of samples. Predetermined sampling protocols have been chosen for the present investigation. Two pre-washed polythene bottles having 1 and 2 L capacities with stopper were used for the samples collection as per CPCB guideline and store for further analyses.

#### **2.3 Method used for the river water quality assessment**

In this study essential physicochemical parameters were recorded during premonsoon 2019 and analyzed in the laboratory according to standard procedures [41]. Various physicochemical parameters like temperature, pH, turbidity, total dissolved solids (TDS), total suspended solids (TSS), total hardness, biochemical oxygen demand (BOD), dissolved oxygen (DO), carbon dioxide (CO2), electrical conductivity (EC), chloride, sulfate, nitrate, phosphate, total alkalinity, chemical oxygen demand (COD), fluoride (F− ), cadmium (Cd), iron (Fe), lead (Pb), chromium (Cr), copper (Cu), manganese (Mn), cobalt (Co), nickel (Ni) and zinc (Zn) were analyzed.

### **2.4 Determination of anionic surfactant through methylene blue active substances method (MBAS)**

The sample 20 mL was transferred into a 40 mL vial (vial A) equipped with a screw cap and teflon liner. The alkaline buffer (2 mL), neutral methylene blue *Evaluation and Quantification of Anionic Surfactant in the Gomti River at Lucknow City, India DOI: http://dx.doi.org/10.5772/intechopen.93517*


**Table 3.**

*Operating condition of atomic absorption spectrophotometer (AAS).*

solution (1 mL) followed by chloroform (5 mL), were added to vial A in successive order. The vial was tightly closed using a holed screw-cap and teflon liner before being vigorously shaken for 2 min using a vortex mixer. After being shaken, the screw-cap was loosen to release the pressure inside and awaited the phase to separate. Once the two phases were separated, a Pasteur pipette was used to transfer the bottom (chloroform) layer into the new vial (vial B) that contained ultra-pure water (22 mL) and acid methylene blue solution (1 mL). Vial B was then shaken using a vortex mixer for 2 min. The cap was then loosened for few seconds and re-tightened. After the chloroform had completely separated from the water (after 2 min), the chloroform layer was collected using a Pasteur pipette and placed in a 10 mm quartz cell. The absorbance of the chloroform phase was measured by using a UV spectrometer at a wavelength of 650 nm. The concentration of anionic surfactants as MBAS is calculated from the calibration curve established with appropriate reference material such as sodium dodecyl sulfate (SDS) (0.05, 0.1, 0.5, 1.0, 1.5 and 2.0 μM).
