**3. Sustainable production of quality feed**

About 80–89% of fresh water that is drawn every day is used for non-potable agricultural purposes in agro-economic regions [27]. This needs to be checked urgently to protect 40% of the world population from facing scarcity of fresh water by 2025 [25]. However, the agricultural practices cannot be avoided to sustain the lives of the ever increasing population of human. Similarly, fodder production is also a must, desirably green fodder for sustaining dairy industry directly, and the human population indirectly.

The agricultural practice consumes chemical fertilizer in addition to fresh water. However, only 12–30% of it is utilized while the rest pollutes the ground water

and the surface water bodies due to leaching [28]. Adequate scientific intervention leads to development of bacterial formulations which ensures entrapment of plant growth nutrients in the root zones by the microbes ensuring minimal leaching into the surrounding environment [29] and hence continuous access to nutrients during the growing season resulting in faster maturation of the crops [21, 28–30].

To address this requirement of sustaining agriculture without fresh water consumption and chemical fertilizer leaching, the liquid biofertilizer developed from bioconversion of dairy wastewater using well characterized bacterial biofilms was used for pot trial experiments followed by field trial experiments. A significant increase in production of mung bean (2.12 folds compared to chemical fertilizer) with enhanced chlorophyll content (1.4 folds compared to chemical fertilizer) of the leaves indicated health growth of the plants.

While the seeds serve as food for human consumption, its husk and the green plant serves as fodder. The maturation of plants was faster with liquid biofertilizer application showing shorter roots with fewer nodules than chemical fertilizer treated plants. The shorter roots with fewer nodules indicate easy access of nutrients in the root zone which neither needs to penetrate deep into the soil, nor establish association with rhizosphere bacteria for nitrogen fixation [16, 21].

In case of pot trial of sorghum sudan grass, there was 3.5-fold increase in biomass production compared to control (without fertilizer), hence ensuring enhanced supply of fodder per unit land without use of fresh water and chemical fertilizer. In case of field trial, sorghum sudan grass showed an increase of 2.53 folds within 2 months of growth.

In case of mung bean, the peak production was obtained within 18 days of podding and was significantly higher than chemical fertilizer grown plants. The production was increased by 2.09 folds if considered for the standard growing time of 65 days while was 1.56 folds higher when compared to chemical fertilizer grown production after 75 days. Faster maturation ensured higher fodder within shorter time with availability of land for the next crop.

In case of black gram a similar production (1.04-folds) was seen compared to chemical fertilizer during field trial. This biofertilizer enhanced the cob yield in maize (*Zea mays* var. Vijay) by 1.19-fold with associated biomass increase which serves as a fodder. The liquid biofertilizer caused 2.1–2.64-folds increase in biomass of lemongrass (*Cymbopogon citratus* var. Dhanitri and var. Krishna) with significant enhancement in oil content. Lemon grass addition to animal feed in definite proportion is reported to enhance nitrogen uptake, leading to healthier growth of animal [31–33]. When compared to chemical fertilizer, the liquid biofertilizer enhanced yield of ramie fiber (1.39-folds), sweet potato tubers (1.44-folds), cassava tuber (1.86-folds), yam tuber (2.55-folds) and elephant foot yam tuber (3.8-folds).

The yield was similar to chemical fertilizer in case of field pea seeds (1.16-folds), colocasia tubers (1.01-folds) and sugar cane (1.01-folds) indicating the biofertilizer to be as effective as chemical fertilizer. This biomass in case of colocasia showed significant increase (2.05-folds increase). Similarly, higher production was seen in case of sugar cane, cassava and sweet potato biomass, indication towards enhancement of fodder crops.

Through this approach, the fodder production around the rural dairies could be sustained round the year with no additional cost as a zero discharge technology considering the effluent treatment plant and the surrounding field [21]. The environment is protected as well as the fresh water reserves will be preserved. The access liquid biofertilizer could also be sold to the neighboring farm owners by the dairy effluent treatment plant owners at a very subsidized rate, which would be beneficial for both the seller and the buyer making the dairy effluent treatment plant operation self-sustainable.

*Green Gold from Dairy Industry: A Self-Sustained Eco-Friendly Effluent Treatment Plant DOI: http://dx.doi.org/10.5772/intechopen.101254*

### **4. Urban dairy wastewater treatment**

The above approach can work only in case of rural dairies [21] with vast farm lands in its vicinity. However, microbial approach with tailor-made consortium can also work in case of urban dairies with space limitation. Appropriately designed consortium using well characterized microbes from activated sludge of dairy effluent treatment plant and other environmental origin can be combined in definite proportion to give a sludge free biofilm based dairy wastewater treatment system which within 20 h of incubation under ambient condition in a single unit operation can reduce the nitrate and phosphate substantially [20]. The treated water after further treatment with bacteria microalgae mixed consortium for 48 h was free of nutrients and suitable for discharge or reuse [26].

The biomass can be used as the raw material for biofuel production due to its high lipid and carbohydrate content. Another advantage of this technique is the growth of the consortium as attached biomass. That makes the harvesting of the biomass less energy intense (as centrifugation is not required) with no requirement for external supply of nutrients and fresh water for growing the microalgae. The dairy wastewater substitutes for the fresh water and the nutrient and hence makes algal growth for biofuel production an economically viable process. The requirement of 48 h compared to 5–7 days during conventional algae based wastewater treatment makes the process rapid and hence requiring less space for treatment. The total time required for the combined treatment of 68 h (bacterial plus the microalgae bacterial) is still less than the conventional system of 120 h [23]. In addition, each process is a single unit operation, hence saving in terms of land involvement.

The dairy wastewater could also be treated using pure bacterial isolates in biofilm reactors capable of removing ammonia, nitrate and nitrate within a much shorter time (depending on the initial pollutant concentration) [34] for reuse in aquaculture, again saving wastage of fresh water from being used for dilution of the wastewater before it could be used for aquaculture.

## **5. Conclusion**

It can be concluded that microbial technology application for dairy wastewater treatment can lead to solving two of the major concerns of the dairy industry namely, (i) ensuring round the year green fodder for the cattle without wasting fresh water and using little chemical fertilizer, as well as (ii) making its effluent treatment plant operation ecofriendly and self-sustainable. The crux of the problem is in developing the right combination of microbes which would convert the pollutants into a plant usable form, resulting in little dead mass generation. This liquid biofertilizer, unlike the conventional organic fertilizers available, release nutrients at sustained, sufficient rate from the beginning of the cultivation resulting in higher yield. Hence health crop in high quantity can be produced from the byproduct (green gold) generated from the dairy effluent treatment process.

#### **Acknowledgements**

The author acknowledges the financial assistance from University Grants Commission-Department of Atomic Energy, Government of India under the CRS scheme [UGC-DAE-CSR-KC/CRS/19/TE07/1069/1085]; Biotechnology Industry Research Assistance Council, Government of India under the Biotechnology Ignition Grant [BIRAC/KIIT0200/BIG-10/17]; and Ministry of Education under

the Frontier Area of Science and Technology scheme [F. No. 5-1/2014-TS.VII dt 7th Aug 2014] for carrying out the study. She acknowledges the hard work done by the scholars and students at Microbial Technology Group at Maulana Abul Kalam Azad University of Technology West Bengal (between 2010 and 2020) as well as Tripura University between (2016 till 2021) which led to the generation of the published data that have been referred here. She acknowledges the intellectual input of Dr. L.M. Gantayet during the wastewater reactor design and related studies; Prof. R Nath for the third party validation of the liquid biofertilizer efficacy. She acknowledges the whole hearted support from the three dairy farms (Mother Dairy, Kolkata, India; OMFED Dairy, Bhubaneswar, India and Gomati Cooperative Milk Producers' Union Limited, Agartala India) for developing the consortium and testing the biotreatment at Pilot scale. The author acknowledges Tripura University and Maulana Abul Kalam Azad University of Technology West Bengal for the infrastructure for carrying out the work.
