2. Materials and method

### 2.1 Study area

The study area Mysore city has 887,446 people [10]. Mysore is located at 12° 180 N 76° 390 E 12.30° N 76.65° E and has an average altitude of 770 m (2,526 feet) [11]. The rainy season is from May to October with an average rainfall 782 (697– 904) mm. The city has been provided with three wastewater treatment plants (Kesare, Vidarayanapuram and Rayankere). All the treatment plants have facultative aerated lagoons and sedimentation basins [12].

#### 2.2 Sampling and analysis

Assessment of water parameters was carried out in March 2016 to May 2016. Water samples were collected from different stages, i.e., raw wastewater, after facultative pond and final effluent (after sedimentation) in cleaned/sterile 2-L polythene bottles as per the standard methods [13].

These samples were analysed for different physico-chemical, microbial and irrigation quality parameters and agricultural application. Analysis and collection of samples have been done according to standard methods prescribed by the American Public Health Association [13].

#### 2.3 Physico-chemical parameters

Temperature, pH, electrical conductivity (EC), TDS, sodium (Na2+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), total alkalinity (as CaCO3), total hardness (as CaCO3), dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD), etc.

#### 2.4 Microbial parameters

The total coliform count was performed by multiple tube fermentation technique using a set of three tubes inoculated with 10 ml of lactose broth of different strength with samples of 10, 1 and 0.1 ml, respectively [2, 14].

#### 2.5 Irrigation quality parameters

The parameters for irrigation of water quality were calculated based on the result obtained after determination/estimation of sodium (Na2+), potassium (K+), calcium (Ca2+), magnesium (Mg2+) and total alkalinity (as CaCO32�) in mg/l. These values of respected cation and anions were used in the following calculations of the respective parameter of irrigation quality for getting its index or ratios.

#### 2.6 Agricultural application

All the samples were subjected to analysis of various physiochemical parameters with concentration on COD, alkalinity, hardness, K+, Na+, Mg+ and Ca+ followed by the methods of APHA [13].

Assessment of Microbial Load Reduction Efficiency of Sewage Treatment… DOI: http://dx.doi.org/10.5772/intechopen.82248

Three different seeds green gram (Vigna radiata), Bengal gram (Cicer arietinum) and green peas (Pisum sativum) were used for the study. A seedling tray was filled with soil and prepared for seed sowing. The healthy and uniform seeds were cleaned with distilled water, and replicates of five seeds were sown for each of the four different, namely, raw wastewater, final effluent, activated charcoal/sand-filtered effluent and distilled water (control). The seedlings were treated with about 10 ml of sample for twice daily, and also the same was treated with distilled water that was set as control. The sampling study was carried out for a period of 7 days after which the seedlings were studied for different characteristics [15].

Percentage germination was calculated by dividing the number of seedlings germinated with the total number of seedling sown for each treatment set.

$$\text{\% generation} = \frac{\text{N}\_{\text{G}}}{\text{N}\_{\text{S}}} \times \mathbf{100}$$

where NG is the number of geminated seeds and NS is the total number of seeds sown.


#### 3. Results and discussion

#### 3.1 Physico-chemical parameters

Determination of the general efficiency depends on the overall performances of the different plants in terms of average removal of indicator parameters including TDS, COD, BOD5, etc. Some of the parameters such as pH directly affect the performance of a secondary treatment process [16] because the existence of most biological life is dependent upon narrow and critical range of pH.

The amount of total dissolved solids (TDS) of inlet as indicated in Figure 1 ranges from 717 mg/l as observed at Vidarayanapuram STP to 466 mg/l at Kesare STP and has shown little reduction over the stages of all three treatment plants. This proves that aerated lagooning treatment process is inefficient in the removal of TDS. Since the effluent of the three plants is being used for agricultural application or irrigation, the high TDS level may affect the porosity of the soil where this effluent is being used.

The plants have shown an overall biochemical oxygen demand (BOD) removal efficiency of 90, 87 and 97% at Kesare, Vidarayanapuram and Rayankere, respectively. The highest removal is associated with sedimentation tank with an average BOD removal 79% as compared to 54% average removal which was recorded in aerated tank for all plants. Similarly, the plants have an overall average chemical

Figure 1. Physico-chemical stage-wise efficiency of the STPs.

oxygen demand (COD) removal efficiency of 81%, and the high removal is still sedimentation tank with an average removal of 60% as opposed to 53% removal in aeration tank. This makes all the three sewage treatment plants efficient in terms of BOD and COD removal, and they are within the CPCB.

As observed in Figure 1, the conductivity of the water has shown no significant reduction over different stages in all the treatment plant. Conductivity increases with the increase of ions, and it is also effectively a surrogate for total dissolved solids and is important for irrigation because it is a measure of the salinity of the water. Salinity is known to restrict water available in the soil for plants to use and also impact crop's physiology and yield.

In the present study, EC of untreated UWW shows a range from 1031 μS/cm at Kesare STP to 1556 μS/cm at Vidyaranyapuram STP. EC of treated UWW showed a range from 976 μS/cm at Kesare STP to 1755 μS/cm at Vidyarayanapuram STP, and the values of untreated and treated UWW at all the three locations lie within the slight to moderate range of the FAO irrigation water quality standards. There was also no significant difference in the alkalinity at different treatment stages of all sewage treatment plants although the water at different location differs significantly in both parameters.

Hardness is usually reported as equivalents of calcium carbonate (CaCO3) and is generally classified as soft, moderately hard, hard and very hard. It is commonly associated with two polyvalent cations, viz. calcium (Ca2+) and magnesium (Mg2+).

As from the results in Figure 1, the UWW in Mysore city falls between 75 and 150 mg/l which is classified as moderate hard with the exception of Kesare STP and Rayankere STP final effluent with 55 and 45 mg/l which is in the class of soft water. The effluent from the aerated lagoon in Rayankere STP is also an exception with a total hardness of 180 mg/l which is in the class of hard water as per the US Environmental Protection Agency (EPA). Hardness has no significant effect in the treatment system, but if this water mix with domestic or industrial water sources, it has a significant effect on the amount of detergent and soap required. It also has

Assessment of Microbial Load Reduction Efficiency of Sewage Treatment… DOI: http://dx.doi.org/10.5772/intechopen.82248

causes scaling in boiler and other industrial equipment when it is used and therefore reduce equipment overall efficiency.
