3.3.1 Irrigation parameter

Although potassium is not an essential part of any plant component, it is known to be involved and physiological process such as plant water balance and protein synthesis which are important in plant growth. Potassium in UWW originates from human faeces and urine disposal, as human faeces has on average 1.6% and urine has 3.7% (dry weight) potassium. The concentration of potassium of untreated UWW was 18, 19 mg/l for the final effluent and 35 mg/l for the AC/sand column treated effluent as indicated in Table 1.

### 3.3.2 Sodium absorption ratio (SAR)

SAR indicates the effect of relative cation concentration on sodium accumulation in the soil. The present study shows SAR in UWW, final plant effluent and the activated charcoal/sand-filtered effluent to be 11.18, 6.1 and 13.08 respectively (Table 1).

SAR in the untreated and AC/sand-filtered water lies in the acute range with respect to sodium irrigation water hazard, while SAR of the treated effluent lies within the slight to moderate hazard. This means that farmers using the reclaimed water need to take extra care whenever they are using this water. Hence, to

Figure 2. Coliform count at different treatment stages.


#### Table 1.

Irrigation parameters of water used in the germination test.

properly assess the suitability of a particular irrigation water supply, the apparent salt tolerance of the specific crop must also be taken into consideration.

## 3.3.3 Residual sodium carbonate (RSC)

It is another alternative measure of the sodium content in relation with Mg and Ca. Residual sodium carbonate (RSC) exists in irrigation water when the carbonate (CO3) plus bicarbonate (HCO3) content exceeds the calcium (Ca) plus magnesium (Mg) content of the water. Where the water RSC is high, extended use of that water for irrigation will lead to an accumulation of sodium (Na) in the soil. If the RSC < 1.25, water is considered safe, while if the RSC > 2.5, the water is not appropriate for irrigation. On this index, both untreated and treated wastewaters are unsafe or inappropriate for irrigation purposes with RSC of 4.6 and 3.11, respectively. The AC/sand-filtered water however lies in the safe range with RSC of 0.56 which is less than 1.25.

#### 3.3.4 Soluble sodium percentage (SSP)

' It is also used to evaluate sodium hazard. Water with SSP greater than 60% may result in sodium accumulations that will cause a breakdown of the soils physical properties. The calculated values of SSP varied from 48.88, 33.49 and 54.55% for untreated UWW, final plant effluent and activated charcoal/sand-filtered effluent, respectively.

#### 3.3.5 Kelly's ratio or Kelly's index

' Suitability of water for irrigation purposes is also assessed on the bases of Kelly s ' ' ' ratio. Ratio of sodium versus calcium and of sodium versus magnesium is used as s ratios. Water having Kelly s ratio of more than one (>1) is considered not s ratio of the water samples tested was 0.78, Kelly suitable for irrigation purposes. Kelly

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

0.69 and 0.88, which implies that this criterion of the groundwater is suitable for irrigation purposes.

## 3.3.6 Effluent effect on seedling

The germination studies indicate that the percentage germination (Figure 3) of each of the three seedlings used for the study varies with different water treatment. The overall high germination rate was observed in raw sewage with 100% germination in both Bengal gram and green gram and 80% germination in green peas, while the least percentage germination was recorded with AC/sand-filtered effluent where a maximum of 80% was recorded for both Bengal gram and green gram and 60% germination in green peas.

This suggest that the percentage germination is not really depended on the concentration of the effluent as it was concluded by the previous study done in Mysore which concluded that the higher concentration of the effluent retards seed germination, whereas the lower concentration may enhance the growth [15]. Bengal gram has the highest germination percentage of 100% almost in all water treatment with only an exception of AC/sand-filtered effluent where only 80% germination was observed. Green peas on the other hand has the lowest overall percentage germination which recorded 80% germination for both control and raw sewage, while only 60% of the seeds germinated in the final effluent and AC/sand-filtered effluent (Figure 3).

Seed germination unlike general seedling growth and yield mainly depends on the basic factors such as light, moisture, air, temperature, etc. and therefore is not really affected by pollutant in water. Green gram was observed to have the highest overall growth of 8.65 cm on average under control treatment compared to 6.3 and 8.65 cm of green peas and Bengal gram, respectively; there is however no much difference in the average length of each seedling among treatment (Figure 3).

Figure 3.

(a) Percentage of different seeds under different water treatments; (b) mean shoot length of different seeds under different water treatments; and (c) mean root length of different seeds under different water treatments.

#### Water and Wastewater Treatment

#### Figure 4.

(a) Vigour index of different seeds under different water treatment; (b) wet weight of different seeds under different water treatments; and (c) dry weight of different seeds under different water treatments.

The treated effluent have the highest average root length for the green peas and green gram seedling of 5.02 and 8.26 cm, respectively, while Bengal gram was high in raw sewage treatment 6.84 cm on average. This high root formation in reclaimed water as opposed to the control can be attributed to the presence of nutrients in it that can act as plant growth enhancer. Overall, green gram has shown a highest vigour, while green peas have the lowest vigour across all treatment. It is also important to note that among all the treatment the highest were recorded in the final effluent and raw sewage, and this can still be attributed to the nutrient and ion content that is associated with this water (Figure 4(a)).

Both wet weight and dry weight as indicated in Figure 4(b) and (c) have no relation with water treatment parameter. The highest weight recorded in both wet and dry was for Bengal gram, and green gram has recorded the lowest wet and dry weight.

#### 4. Conclusion

The aerated lagooning treatment system used has proven to be effective in the reduction ofsome of the parameters and ineffective in some. Parameterslike BOD and COD of treated effluent in UWW are within the CPCB permissible limit for disposing the UWW on land for irrigation. Continuous use of this effluent may however have a negative impact on the soil since some of the irrigation parameters like EC, TDS and SAR are over the average range of the FAO irrigation water quality standards.

The aerated lagooning treatment used in UWW has proven to be ineffective in the treatment or reduction of coliform bacterial which is used as a surrogate organism for microbial pathogens. This may be partially due to the chosen treatment system, but the operation and maintenance can also have an effect on the efficiency of the treatment.

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