**3. Results**

A summary of the liquid effluent from the paper mill at various stages of the treatment process are presented in **Table 2**. Most effluent parameters decreased or reduced as we moved from the primary clarifier to the final stabilization pond prior to discharge into the river and the difference was statistically significant (p < 0.05). Only turbidity and color of the treated effluent increased markedly. For example, the effluent color increased on average by almost 250% from 133 OH to 331 OH, while its turbidity rose by 155%, from 1574 NTU to 2431 NTU.

**Table 3** summarizes emission estimates from the Kraft Paper mill in Western Kenya. The volume of total reduced sulfur (TRS) was still high during the study, and


*Distribution of Potentially Toxic Elements in Water, Sediment and Soils in the Riparian… DOI: http://dx.doi.org/10.5772/intechopen.102440*

#### **Table 2.**

*Raw and treated Kraft pulp and paper mill effluent by current treatment system (\*source: Kenya effluent discharge standard. 3rd schedule).*

confirmed the characteristic strong foul smell in and around the mill. The concentration of Cu, Pb and Cr remained relatively high, while Zn, Ni and Cd were low over the course of the study period.

The river Nzoia's water physico-chemical parameters results within the three sampling sites (WIP, EDP and DSP) are presented in **Table 4**. Temperature, pH and electrical conductivity (E.C) in the three sites exhibited significant variations (p < 0.05) (Type III, One-Way ANOVA). Temperature, pH and EC were significantly higher at EDP as compared to other sites but there was not enough evidence of significant difference in pH between WIP and DSP sites.


*a Emission Factors expressed in unit weight of air –dried unbleached pulp (ADP) from Recovery boiler and direct evaporators –Controlled by Electrostatic Precipitators from US EPA, 1990. <sup>b</sup>*

*TRS (Total Reduced Sulfur) includes methyl mercaptan, dimethyl disulphide, and hydrogen sulphide. d Emission factors from [42].*

#### **Table 3.**

*Estimated Kraft pulp mill emissions.*


*\*Mean values SEM followed by different superscripts 'a' or 'b' across the rows are significantly different at α = 0.05. Mean values across the rows with the same superscripts 'a' are not statistically different at α = 0.05. For example, the pH at DSP is not statistically different from the pH value at WIP because it carries the same superscript 'a'.*

#### **Table 4.**

*\*mean values SEM of the physico-chemical parameters along the sampling sites at PanPaper Mills, Webuye, Kenya during the study period.*

The results for lime mud and recovery boiler ash in **Table 5** showed their pH level, Cd and Zn concentrations were not significantly different, but the moisture content, Pb and Cu concentrations were significantly higher in lime mud compared to recovery boiler ash (p < 0.05). In terms of chemical compositions, calcite (calcium carbonate and calcium oxide) was probably the major component of lime mud, while recovery boiler ash was mainly composed of burkeite (sodium carbonate sulfate), aphthitalite (potassium sodium sulfate), and halite (sodium chloride).
