**4.3 Characteristics of wastewater from Central Region of Ghana**

#### *4.3.1 Composite characteristics of palm oil mill wastewater*

The composite characteristics of wastewater from the small-scale palm oil processing in Central Region of Ghana are summarized in **Table 4** compared with the Ghana effluent discharge standard, characteristics of palm oil mill wastewater from


*Oil and fat processing industry includes oil and palm, shear butter, peanuts, coconut oil, palm kernel, etc. Source: GSA [25].*

#### **Table 3.**

*Effluent standard for oil and fat processing industry in Ghana.*


*All values are in mg/l except pH.*

*TS-total solids; TDS-total dissolved solids; TSS-total suspended solids.*

*Figures in bold are outside the Ghana effluent discharge limits.*

#### **Table 4.**

*Characteristics of palm oil mill wastewater from small-scale mills in the Central Region of Ghana and literature.*

small-scale processing mill in Nigeria and a large-scale mill in Malaysia. The wastewater contained solids, oxygen-consuming compounds, nutrients (nitrogen, phosphorus and potassium) and oil and grease. Around 13–22% of the total solids and 20–23% of suspended solids were in the form of oil and grease.

The COD:BOD5 was 2.1–3.1 (mean = 2.5) indicating the presence of slowly biodegradable organic matter as noted by Henze, van Loosdrecht [28]. This may be attributed largely to the unrecovered fats and oils in the wastewater as noted by Cisterna-Osorio and Arancibia-Avila [29]. It has been reported that, slowly biodegradable COD constitutes 45% of the total COD of raw palm oil mill wastewater with only

*Small-Scale Palm Oil Production in Ghana: Practices, Environmental Problems and Potential… DOI: http://dx.doi.org/10.5772/intechopen.106174*

about 20% being readily biodegradable due to the free fatty acids [30]. Low pH of wastewater from palm oil processing is also due to the organic acids formed during fermentation of the palm fruits [31]. The acidity of palm oil and, by extension, the palm oil mill wastewater have been reported to be affected by the extraction procedure, presence of microorganisms and the genotype of the palm tree [32]. Suspended solids in the wastewater consists of carbohydrates with oil and other organic and inorganic solids [27]. Most of these solid constituents could serve as nutrient sources for microorganisms.

#### *4.3.2 Seasonal characteristics of palm oil mill wastewater*

The wastewater characteristics varied with production season (see **Table 5**). The characteristics of wastewater produced during the peak season were generally higher than the lean season except for pH and solids (total and suspended). Irrespective of the production season, the wastewater was characterized by slowly biodegradable organic matter (COD:BOD5 = 2.5–2.6).

Boiling and clarification time during the lean season are mostly greater than the peak season due to lower processing cycles. A longer clarification time corresponds to greater oil extraction rate, higher evaporation, lower moisture content and higher solids in the wastewater. This reflects the higher concentration of solids in wastewater produced during the lean season as compared to the peak season. The differences in the mean pH, TDS and total nitrogen were significant at 1% level. Potassium concentration in the peak season was significantly higher than the lean season at 3% level. The seasonal variation for TS, TSS, BOD5, COD, Phosphorus and oil & grease were statistically insignificant. It could be deduced from the results that similar organic and solid loading rates may be used for designing treatment system to handle wastewater for both the peak and lean seasons.


*All values are in mg/l except pH.a Peak season minus lean season.*

*\*Significant at 3% level.*

*\*\*Significant at 1% level.*

*Source: Authors.*

#### **Table 5.** *Seasonal characteristics of palm oil mill wastewater.*

### *4.3.3 Characteristics of different wastewater streams*

The characteristics of the wastewater from boiling and clarification sampled during the peak and lean production seasons are presented in **Table 6**. For both production seasons, the pH, TDS, BOD5 and COD of the wastewater from boiling were higher than for clarification. For the remaining parameters (TS, TSS, oil & grease, total nitrogen, phosphorus and potassium) the clarification wastewater was higher than the wastewater from boiling. Apart from BOD5 and COD, the trend of the results was consistent with the characteristics of individual wastewater streams reported in Malaysia.

The COD:BOD5 was 2.3–2.4 for wastewater from boiling and 2.6–3.1 for wastewater from clarification. The biodegradability of the wastewater from boiling would be better than the wastewater from clarification. The higher COD:BOD5 for wastewater from clarification compared to boiling may be attributed to the higher fat and oil content of the wastewater from clarification. The differences in the mean concentration of parameters between boiling and clarification were statistically significant at 1–2% level.


*\*\*Significant at 1% level. Source: Authors.*

#### **Table 6.**

*Characteristics of wastewater from boiling and clarification for peak and lean production seasons.*

*Small-Scale Palm Oil Production in Ghana: Practices, Environmental Problems and Potential… DOI: http://dx.doi.org/10.5772/intechopen.106174*

#### **4.4 Wastewater management practices and potential environmental impacts**

#### *4.4.1 Wastewater management practices in the Central Region of Ghana*

Assessment of the twenty-five (25) small-scale processing mills revealed that none of the mills had a wastewater treatment facility. Consequently, untreated wastewater generated from the extraction processes were discharged on the land or through drains to nearby bushes (**Figure 6**).

Similar environmentally unfriendly wastewater disposal practices by small scale mills have been reported in Nigeria [16]. Contrary to other observations [15], none of the mills assessed in this study disposed their wastewater directly into streams or rivers. Nevertheless, in all the mills assessed, the areas where wastewater was disposed had lost their vegetation. This confirms observations in Africa by Poku [10] that the bushes near the small-scale mills where wastewater is disposed die slowly. Moreover, a very strong stench characterizes the processing mills possibly due to the decomposing wastewater.
