Handbook for Irrigation of Wine Grapes in South Africa

TABLE 5.11. Legislated limits for COD, faecal coliforms, pH, EC and SAR for irrigation with wastewater in South Africa (Matthews, 2008). Parameter Maximum irrigation volume allowed (m 3 /day) < 50 < 500 < 2 000 COD (mg/  ) 5 000 400 75 Faecal coliforms (per 100 m  ) 1 000 000 100 000 1 000 pH 6-9 6-9 5.5-9.5 EC (mS/m) 200 200 70-150 SAR <5 <5 Other criteria apply MUNICIPAL WASTEWATER Using treated municipal wastewater for irrigation is not an uncommon practice. Currently ca. 2 000 ha vineyards in the Swartland region are being irrigated with treated wastewater from the city of Cape Town, i.e. the Potsdam irrigation scheme, and the Malmesbury municipality. Analyzing the treated wastewaters during mid- summer in vineyards near Philadelphia and Malmesbury for ten and five years, respectively, revealed that most element concentrations were within acceptable limits (Fig. 5.12). Likewise, the pH, EC and SAR, as well as Fe, B and Mn were within acceptable limits (Fig. 5.13). Levels of P, N, trace elements and heavy metals were only determined in the treated municipal wastewater from the Potsdam scheme. The average PO 4 , NH 4 -N and NO 3 -N concentrations were 4.1, 2.7 and 2.1 mg/  , respectively. Trace element, i.e. Cu and Zn, as well as heavy metal, i.e. Cr, Pb and Hg concentrations were extremely low or undetectable (data not shown). 5.6.1

Figure 5.12

300

Philadelphia Malmesbury

250

100 Concentration (mg  ) 150 200

50

0

Ca

Mg

K

Na

HCO3 SO4

Cl

FIGURE 5.12. Element concentrations in treated municipal wastewater used for irrigation of vineyards near Philadelphia and Malmesbury, respectively.

Figure 5.13

8 9

124 CHAPTER 5 – IRRIGATION WATER QUALITY

Philadelphia

Malmesbury