The demand for dairy products is increasing each year, with a consequent continued expansion and development of the dairy processing industry globally. Increased production of dairy products means increased production of dairy industry wastewater. This generates a need to better understand the characteristics of dairy wastewater to better manage it.
Dairy industry overview
The dairy processing industry covers a broad range of food and beverage products, each producing different flows and loads of wastewater and dairy effluent with distinctive characteristics. The following page gives an overview of the types of dairy products, with a specific focus on dairy wastewater composition and characteristics. This will allow you to understand dairy wastewater, which is the first step in understanding how to clean and treat it.
Dairy industry wastewater is typically white in colour with an unpleasant odour. It has a high pollutant load, with significant concentrations of COD [chemical oxygen demand], BOD [biological oxygen demand] and TSS [total suspended solids]. In addition to this, there can be high nutrient concentrations in the form of P [phosphorous] and N [Nitrogen]. Other pollutants can also be present in the dairy effluent in high concentrations. These pollutants include fats, oils, detergents, casein/whey and salts.
Dairy industry wastewater volume
Water plays a particularly significant role in the dairy sector, as it is used in every step of processing. From cleaning and washing, to heating and cooling. To put it in perspective, it is estimated that to produce 1L of milk, 2.5L of water are needed. For other dairy products, a general estimate is that for 1 tonne of dairy product produced, 1m3 of dairy effluent is produced. Wastewater flows are highly variable in most dairies due to washing processes.
Washing and CIP generates a significant amount of wastewater, as each milk product requires a separate technological line. Seasonal variations also occur when milk production peaks in summer months. The amount and characteristics of dairy industry wastewater is also influenced by the factory size, CIP methods and good manufacturing practice.
Dairy industry wastewater categories
Despite there being various milk-based products, dairy industry wastewater can still generally be categorised into three main sources. These are process water, cleaning water and sanitary wastewater.
Process Water
Dairy process water can arise from the cooling of milk and from the evaporation of whey or milk for powdered milk products. The characteristics of dairy wastewater from these processes is a high volume, but a low pollutant concentration. This means that process water can often be treated and then reused.
Cleaning Water
CIP wastewater is from clean in place activities. Cleaning uses a significant amount of water across the full food and beverage sector due to hygiene requirements. CIP wastewater from dairies can be highly polluted as it contains products and ingredient residues, in addition to detergents and disinfectants used in the cleaning process. The characteristics of dairy wastewater from CIP activities is very different to process water.
Sanitary Wastewater
Sanitary wastewater refers to the sewage generated from toilet use, showers and washing facilities. The volume of this wastewater is generally smaller, and it can be treated in conventional onsite sewage treatment plants or directly by the municipal wastewater treatment plant without the need for pre-treatment. As a result, sanitary wastewater is not discussed further.
Breadown by types of dairy product
The number of dairy based food and drink products in extensive. From pure dairy products such as raw milk, to whey and casein which are used as ingredients and supplements in non-dairy based foods. A summary of the main dairy product categories is given below, with information on the specific, key characteristics of the dairy industry wastewater that is produced from their manufacturing.
Butter products
A wide range of butter products are manufactured globally. Cream is used as the main raw material for dairy based butters. The dairy industry wastewater generated from butter manufacturing and butter processing contains considerable amounts of fat. A corresponding high COD is also present in butter processing wastewater.
| Butter products | |||||||
|---|---|---|---|---|---|---|---|
| Raw cream butter | Clarified butter | Cultured butter | Mild cultured butter | Butterfat | Butterfat | Whey butter | Liquid separated during butter production |
Special cleaning detergents that can emulsify the fats and oils then make their removal and separation more difficult with basic fat traps and skimmers, resulting in a need for more advanced separation and wastewater treatment processes.
| Parameter | BOD | COD | FOG | TSS | TN | TP |
|---|---|---|---|---|---|---|
| Value mg/l | 200-2500 | 7500-9000 | 3000 | 700-5000 | – | – |
Cream products
Cream is an interim product that is often used to produce other dairy products. Creamery wastewater is dependent on the specific product being manufactured. Cream based products include the following:
| Cream products | |||||
|---|---|---|---|---|---|
| Condensed cream | Schmand | Half and half | Whipping cream | Clotted cream | Pasteurised cream |
| Crème fraiche | Sour cream | Table cream | Double cream | Soured cream | |
Cream based products are also characterised by high organic and fat loads, with lower nutrient values. Typical values for different pollutants in cream production are as follows:
| Parameter | BOD | COD | FOG | TSS | TN | TP |
|---|---|---|---|---|---|---|
| Value mg/l | 2500 | 5000 | 1000 | 3000 | – | 15 |
Milk products
Milk covers a broad range of products, but here we focus specifically on milks that are manufactured for the beverage sector. Milk processing wastewater can represent a significant source of dairy industry wastewater and sludge due to the milk volumes processed being remarkably high compared to other dairy products. Milk based products include the following:
| Milk products | |||||
|---|---|---|---|---|---|
| Raw milk | Fresh whole milk | Sterilized milk | Condensed milk | Part skim condensed milk | Cooled and filtered raw milk |
| UHT milk | Extended shelf-life milk | Skimmed milk | Low fat milk | Condensed skim milk | Low fat skimmed raw milk |
While the volumes of milk processing dairy industry wastewater can be high, compared to more processed products, the pollutant loading is generally lower. Typical values for different pollutants in milk production are as follows:
| Parameter | BOD | COD | FOG | TSS | TN | TP |
|---|---|---|---|---|---|---|
| Value mg/l | 500-1300 | 1000-2500 | – | 100-450 | – | – |
Cheese products
A wide range of cheeses are now manufactured, including the broad categories of soft and hard cheeses. The level of processing can be relatively high for cheeses compare to other milk-based products. By products of cheese processing results in the production of other dairy products such as whey. Cheese processing dairy industry wastewater can have a high pollutant load, with fats and salts.
| Cheese products | |||||
|---|---|---|---|---|---|
| Mascarpone | Semi hard cheese | Soft ripened | Fresh cheese | Semi soft | Pasta filata |
| Blue vein / mouldy | Hard cheese | Cream cheese | Sour milk cheese | Brined | Whey cheese |
Cheese effluent can have an exceedingly high pollutant loading and can also contain whey which will have a major influence on the COD levels in the wastewater. Typical values for different pollutants in cheese production are as follows:
| Parameter | BOD | COD | FOG | TSS | TN | TP |
|---|---|---|---|---|---|---|
| Value mg/l | 500-5000 | 1000-5000 | 350-2750 | 200-2500 | 20-850 | 5-300 |
Powdered products
Powdered dairy products produce a dairy effluent that has a high pollutant loading, although not as high as cheeses. The effluent concentration from whey processing effluent has a moderate BOD and COD concentration.
| Powdered products | ||
|---|---|---|
| Powdered whey | Powdered skimmed milk | Powdered milk |
Powdered milk products are harder to categorise when it comes to the wastewater composition, as the manufacturing processes vary. And if there are significant amounts of powder that enter the waste stream the pollutant loading can be extremely high.
| Parameter | BOD | COD | FOG | TSS | TN | TP |
|---|---|---|---|---|---|---|
| Value mg/l | 1500 | 3000 | – | 100-3000 | 250 | 20 |
As can be seen, the characteristics of dairy wastewaters varies. The above referenced values for different dairy processing wastewater and effluent streams are from average data collected during real project assessments for our customers and clients.
Summary
It should now be clear that dairy industry wastewater and effluent treatment is a complex topic. Each specific product being manufactured, and each specific manufacturing process steps can all greatly influence the characteristics of dairy wastewater.
This means that it is critical to understand the composition and characteristics of your dairy industry wastewater, and to then select the correct process technology.
