Dairy industry generates huge amount of wastewaters,
approximately 0.2–10 L of waste per liter of processed milk
[19]. Wastewater generation and characteristics are significantly
affected by several parameters such as scale of the factory, type
of processing, the efficiency and simplicity of methods used for
cleaning of equipment, operating practices, methods used for
Table 1
Dairy industry wastewater characteristics.
Wastewater source pH COD (g L−1) BOD5 (g L−1) Solids (g L−1) Volatile
solid (g L−1)
Nitrogen
(mg L−1)
Phosphorus
(mg L−1)
FOG (g L−1) Reference
Whey 4.46 60 40 59(TS) 1.5 NA NA NA [21]
Whey 4.9 68.6 7.71 1.35 (TS) NA 1120 (TKN) 500 9.44 [22]
Ice-cream 5.2 5.2 2.45 3.9 (TS) 2.6 60 (TKN) 14 NA [23]
Ice-cream 6.96 4.94 NA 1.1 (TSS) 0.99 NA NA NA [24]
Milk permeate 5.55–6.52 55.20–63.48 NA 2.67–3.80 (TSS) NA 300–400
(TN)
350–450 NA [25]
Milk processing 4.0–7.0 5–10 3–5 3–7(TS) NA 20–150
(TKN)
50–70 NA [26]
Dairy 7.12 4.59 NA 4.35 (TS) 2.1 89 (TKN) 9.9 NA [27]
Dairy 8–11 2–6 1.2–4 0.35–1 (TSS) 0.33–0.94 50–60
(TKN)
20–50 0.3–0.5 [28]
Dairy 7.1 5 2.8 3.88 (TS) 1.35 16.5 (TKN) 38.6 NA [29]
NA: not available; TS: total solid, TSS: total suspended solid; TN: total nitrogen; TKN: total Kjeldahl nitrogen; FOG: fats, oil and grease.
effluent disposal, type of water sources and the cost of water
[20]. Some reported characteristics values of dairy wastewaters are
given in Table 1. Dairy wastewater is generally in neutral conditions
whereas pH of ice-cream wastewater is slightly acidic and
it decreases until to 4.46 in whey wastewater. Organic content
of dairy wastewater as in the terms of COD and BOD5 changes
in wide range according to type of processing. COD concentration
in dairy industry is between 2 and 6 g L−1 while it increases
up to 10 g L−1 in milk-processing effluent and the highest values
have been reported for whey wastewater up to 70 g L−1.
Dairy wastewater is also characterized by high concentration of
solids with half of its as in volatile form. The highest reported
amount of total solid was 59 g L−1 in whey while very little amount
was in volatile form. Nitrogen and phosphorus contents of dairy
wastewater are considerably different in each processing effluent
while those were comparatively lower than other industrial
sources.