**3. Factors affecting characteristics of wastewater**

### **3.1 Volume of wastewater**

*Environmental Issues and Sustainable Development*

dairy wastewater making it sustainable in nature.

**2. Characteristics of dairy wastewater**

**Sr. no Details Value (in mg/L) except for pH**

Dairy wastewater comprises of compound organic substances like carbohydrates, amino acids, and lipids which get converted into sugars, acids, and fatty acids upon hydrolysis [9]. Milk is a natural supplement for humans and animals. This consists of various nutrients including protein, vitamin, carbohydrate, and fat [10]. Milk is one of the most valuable items that join commerce, and it is vital as an object of food in daily life. Dairy wastewater contains large amounts of milk components like casein, lactose, fat, inorganic salts excluding detergents and sanitizers that accord greatly towards high BOD and COD [11]. In order to increase milk volumes and improve meat quality antibiotics and antimicrobials have been used in dairy animals at the sub-therapeutic level. This does not only harm the animal's health and well-being, but also significantly affects the health and well-being of humans through the intake of animal products like milk and meat, thereby affecting

wastewater from the dairy industry lies in the presence of carbohydrates, proteins, and fats. 2–2.5 L of wastewater is generated during the processing of every liter of milk [7]. A large number of industries are located around river banks and due to lack of stringent rules and regulations, a large volume of dairy wastewater is released without treatment which goes unutilized and pollutes the environment [8]. Dairy industries are also the potent source for various emerging contaminants specifically estrogens which find their way into the environment through wastewater effluents coming out from dairy industries and livestock activities. The fate of these emerging contaminants is recognized as an issue of public health and environmental concern. The current wastewater treatment technologies are not efficient enough for the removal of these pollutants as these are not monitored regularly due to the lack of stringent rules and regulations for these contaminants. Therefore there is a need to find an innovative technology that serves the purpose. Microbial Fuel Cell (MFC) treatment has gained appreciable interest because of its ability to treat wastewaters and simultaneously leading to the generation of power. This property of the MFC technology makes it suitable for the elimination of such recalcitrant pollutants from

*Standard norms of Central Pollution Control Board of India for dairy effluents (Environment (Protection)* 

1. pH 5.4–9.1 2. Total solids <2200 3. Total dissolved solids (TDS) <2100 4. Suspended solids (SS) <100 5. Total chlorides <600 6. Sulfates <1000 7. Phosphates <5 8. Oil and grease <10 9. Chemical oxygen demand <360 10. Biological oxygen demand <30 11. Nitrates <10

**100**

**Table 1.**

*Rules, 1986).*

Water has an important role in milk processing. It involves cleaning, washing, disinfection, heating, and cooling in every step of the technologies used. There is a massive requirement for water [19]. A large amount of wastewater is generated through manufacturing processes [20]. Contaminated water from sanitary practices amounts to 50–80% of the actual water utilized in the dairy industry, while the rest of the 20–50% is clean water [20, 21]. It has been measured in volume units stating the quantity of wastewater is around 2.6 times more of the processed milk. The characteristics and the amount of the wastewater generated rely mainly on the size of the factory, technology used, efficacy and convolution of clean-in-place methodologies, good manufacturing practices, and so on [2, 5]. However, the world's mean wastewater volume can be decreased from 0.49–36.0 m3 to 0.5–2.0 m3 of effluent per m3 of milk processed with the introduction of GMP [5, 22]. Nowadays, the volumetric charge designed is 1 m3 of effluent per ton of milk produced. The instant discharges installed in the washing of tank on transport trucks, mediator pipelines, or machinery after every cycle are a significant aspect of the volume-based loading of wastewater treatment plants designed for dairies. In these cases, the effluent volumes are greater than those of the milk produced [23]. On average, the amount of wastewater discharged is 70% of freshwater being used at the plant [20]. Effluents from dairy products primarily include milk and its products misplaced in the processing cycles (milk spills, skimmed milk, spoiled milk, and curd remnants), inoculums used in processing, byproducts generated by manufacturing techniques (whey, milk and there permeates), and several additives used in manufacturing [16, 21, 24, 25]. Milk lost in wastewater treatment is about 0.49–2.5% of milk processed, which may rise up to 4% [26].

#### **3.2 Categories of wastewater**

#### *3.2.1 Processing water*

Cooling the milk in separate coolers along with condensation from the evaporation of whey and milk leads to the production of water for fermentation. Vapors are extracted from the milk and whey drying process that after condensation produces the cleanest effluent, but they can also consist of volatile compounds, whey, and milk droplets. Processing waters eliminate toxins, and after minimal pretreatment may be stored or released with stormwater [3]. Water can be reused for systems where the derivative materials are not in close contact. Typical applications involve

hot water, steam manufacturing, and membrane washing. After the final flushing of bottles and condensates from secondary vapors created in vacuum installations, water from liquid cooling during pasteurization can be used for room washing, irrigation, and so on.

#### *3.2.2 Cleaning wastewater*

Wastewater purification typically benefits from cleaning machinery within close contact with dairy goods. This involves spillage of milk and substance, whey pressing or brine, malfunctioning of the clean in place effluents, or machinery errors. More than 93% of the organic contents contained in the effluent are partly the remnants of milk, cheese, whey, butter, sugar, honey, and fruit concentrate or stabilizers. These effluents are found in significant concentrations and are extremely toxic thereby needing more care.

#### *3.2.3 Sanitary wastewater*

Sanitary wastewater is utilized in washrooms, toilets, etc. Sanitary wastewater has parallels with urban wastewater composition and is typically piped straight to sewage facilities. It may be used as a supply of nitrogen for irregular dairy effluents after a secondary aerobic treatment. Furthermore, by-products from agricultural processes like milk, whey, and their permeate can be classified independently if they are segregated individually from other wastewater sources [27, 28].

#### **4. Dairy wastewater treatment**

For the dairy industry, common wastewater treatment strategies involve grease traps, oil-water separators to remove floatable solids, flow equalization, and clearers to isolate suspended solids. Biological treatment consists of the aerobic and anaerobic methodologies. Anaerobic treatment accompanied by aerobic treatment is also used to minimize soluble organic matter (BOD), and the reduction of biological nutrients (BNR) is used to increase nitrogen and phosphorus levels. Biological aerobic treatment requires cellular destruction in the presence of oxygen. Conventional aerobic treatment of dairy manure includes procedures such as activated sludge, batch sequencing generator, revolving biological contactors, trickling pipes, aerated lagoons, or a variation of these.

Treatment of anaerobic wastewater has emerged as a feasible and inexpensive alternative particularly for high BOD removal over conventional aerobic treatment. Anaerobic methods of treatment involve up-flow anaerobic sludge blanket or UASB, anaerobic batch sequencing reactors or ASBR, continuous-flow reactor, hybrid anaerobic digesters, up/downflow anaerobic filter, and various 2-stage processes that use acid and methane forming bacteria. **Figure 1** shows the sequential treatment of dairy wastewater through mechanical, physical, chemical and biological treatment methods [20].

#### **4.1 Mechanical treatment**

This is the initial phase of dairy wastewater treatment and this includes grit pool, skimming tank, and main clarifiers. During further effluent processing, the large floating material is removed by screens, in-turn avoiding the chocking of pipes. Chambers are used for extracting heavier inorganic substances like sand, gravel, etc. The aim of installing skimming tanks is to extract oil, grease, pieces

**103**

*Treatment of Dairy Wastewaters: Evaluating Microbial Fuel Cell Tools and Mechanism*

of wood, skins of fruit; etc. The clarifier helps matter to settle at a very slow rate or sediment at the bottom in the tank. The substance accumulated underneath is

Chemical treatment is also recognized as precipitation. This is performed by adding flocculants to wastewater and vigorous mixing with agitators. This method precipitates insoluble phosphate into larger flocks, in the form of small pellets. In pre-sedimentation basins, the greater flocks settle as the main sludge, whereas a clear supernatant fluid overflows into a lake for biological therapies. Sedimentation lagoons are armed with tools to continuously scrape the sediment towards a sump or

Milk effluent includes organic waste; therefore most viable methods for the elimination of organic content are biological degradation. However, sludge generated may lead to serious and costly problems towards disposal, particularly during the processes of aerobic biodegradation. This can be further worsened due to the tendency of sludge to absorb various organic compounds and poisonous heavy metals also. Nonetheless, biological treatment has the profits of dynamic organic microbial processes and the ability for adsorption of heavy metals effectively. Biological waste management strategies have an immense capacity to incorporate

Microorganisms cultured in an O2-rich environment degrade organics by oxidizing matter to CO2, soil, and cellular material. Aerobic treatment methods include activated sludge reactors, rotating biological reactors, conventional filters for

Anaerobic method of treatment is mainly intended for the biological processing of high strength wastewater. It is a process by which microbes are used in the absence of O2 to digest organic matter by converting it to biogas (CH4 and CO2)

oblique gutters to keep water away from the clarified surface layers [29].

diverse types of biological schemes for selective elimination [30].

*DOI: http://dx.doi.org/10.5772/intechopen.93911*

*Dairy wastewater treatment alternates (adapted from [20]).*

known as sludge [29].

**Figure 1.**

**4.2 Chemical treatment**

**4.3 Biological treatment**

*4.3.1 Aerobic treatment*

trickling, and so on [30].

*4.3.2 Anaerobic treatment*

*Treatment of Dairy Wastewaters: Evaluating Microbial Fuel Cell Tools and Mechanism DOI: http://dx.doi.org/10.5772/intechopen.93911*

**Figure 1.** *Dairy wastewater treatment alternates (adapted from [20]).*

of wood, skins of fruit; etc. The clarifier helps matter to settle at a very slow rate or sediment at the bottom in the tank. The substance accumulated underneath is known as sludge [29].
