Unconventional sewage treatment plant:- In just over three months, the production of ivy gourds in the farm of Bhailalbhai Solanki (65) increased from 40 kg to 60 kg, while his electricity bill went down. A small farmer mainly growing vegetables, Bhailalbhai is the lone direct beneficiary of a first-of-its-kind Unconventional Decentralised Multi-Stage Reactor (UDMSR) set up at Luna in Padra taluka of Gujarat for domestic sewage treatment.

Set up in an area of over 850 sq ft on panchayat land on a pilot basis, the reactor treats 25 Kilo Litres per Day (KLD) of sewage. A part of the treated sewage is used for irrigation in the adjacent agricultural land of Bhailalbhai, while the rest is released into a pond. The project services around 500 people in the village, which has a total population of 2,800. 

With sewage recycled, Bhailalbhai's family is seeing other benefits too. “We have got rid of mosquitoes,” beams Mansi Solanki (15), the granddaughter of Bhailalbhai. Moreover, the family no longer has to put up with the foul smell from the sewage.

Anil Valand (55) is yet to benefit from the pilot project. But he hopes to get treated sewage water for irrigation some day. “It is good to have it. You naturally get fertilisers. It will help increase production by 50%, which means a lot to farmers like me,” he says.

For irrigation, farmers generally use groundwater or the Narmada waters flowing through a canal. However, the groundwater in Padra is critically polluted due to an effluent channel in the area and the industries.

Using treated sewage water would solve the irrigation issue, which would also mean less reliance on groundwater, which ultimately benefits the environment. “Treated sewage water can provide phosphorus, a very important element, to the fields,” informs DM Thaker, Member Secretary, Gujarat Pollution Control Board (GPCB).

Organic farmer Sanjay Gohil (47) lives at Sanda, 14 km from Luna, and doubles up as a treatment plant operator in a multinational company. Gohil says he is waiting for that day when his village would get a similar reactor. 

Bhailalbhai, who studied only up to class 4, has been trained to operate the plant at Luna. Gohil inspects the plant once in a while to see if it is operating well. 

How it works

As per the March 2021 report of National Inventory of Sewage Treatment Plants (STPs) of the Central Pollution Control Board (CPCB), the estimated sewage generation in India is 72,368 Million Litres per Day (MLD). However, the total capacity of installed and operational STPs is 26,869 MLD, which is 37.1% of the total sewage generated. This means 63% of the sewage generated in India goes untreated.

This is where the cost-effective UDMSR developed at the Maharaja Sayajirao University of Baroda can make a difference. The brainchild of Professor Upendra D Patel of the Civil Engineering Department of the university, the reactor takes in the untreated sewage collected near the plant through a small flexible pipe. The treated sewage then accumulates in a low-lying area, before it is released into the pond and farms.  

Dr Patel, along with his students, worked on the reactor for nearly a decade. “When we started experimenting with UDMSR, we were not thinking of taking it to the field. Then I learnt that some of the sewage treatment plants in Ahmedabad were not operating. That was when I realised the urgent need for this technology,” Dr Patel, who has also applied for a patent for UDMSR, tells 101Reporters.

Later, when GPCB took samples from the UDMSR lab model and the results turned out to be good, it was decided to take it to the field. Now, the first on-field trial has been completed successfully. “It can be expanded up to 75 KLD at the present site,” he adds.

Dr Patel explains that they wanted to develop a process that was very easy to operate and does not require any supervision. Initially, the team had tried vermifiltration in the laboratory with an earthen bed and earthworms. However, it was not successful.

To design UDMSR, special layers of media were made using sponge. Bacterial films were developed over it. When the sewage water passed through it, the bacteria took away the chemical oxygen demand and biochemical oxygen demand.

"UDMSR does not require any mechanisms for primary and secondary sedimentation tanks. The capital cost of centralised STPs is about Rs 1.75 cr per MLD and the cost of laying sewer network is about Rs. 4.5 cr per MLD. The biggest advantage of UDMSR is that it can be installed in a decentralised manner circumventing almost entire or most of the cost of laying sewer network," Dr Patel explains.

“The reactor is naturally ventilated. It does not require blowers. In fact, blowers contribute to nearly 50% of the energy cost of a conventional STP... The cost of operation of UDMSR is only one tenth of a conventional STP... Moreover, it does not require any permanent structure and can be installed in the form of a skid. As a result, it can be shifted/altered very easily," he details.

Dr Patel candidly says that the conventional STPs are efficient and they do not fail because of technology problems. However, since they work on suspended growth technology, a person has to daily calculate how much biomass has to be kept in the system and how much has to be thrown out. Energy consumption is also high.

On March 13, the Maharaja Sayajirao University and GPCB signed a memorandum of understanding to disseminate the UDMSR technology in Gujarat. The university will be responsible for the design and detailed engineering of UDMSR system at the locality suggested by the GPCB, besides the supervision of its installation and commissioning. Installation, commissioning and regular operation of UDMSR are the responsibilities of GPCB.

Challenges

Notwithstanding the benefits, it was not easy to convince the villagers. “They feared odour… We had to tell them that we will remove the plant if they experience odour,” Rohit Prajapati, an environmental activist instrumental in setting up the plant, tells 101Reporters.

Today, odour emanates from neither the plant nor the pond that collects the treated water. “People have even put up benches to sit near the pond and a few birds have also been spotted there,” he adds, while pointing to the role the recharged pond could play in enhancing groundwater level.

The 30 KLD reactor cost Rs 9 lakh, inclusive of installation and labour charges. Padra Industries Association contributed Rs 8 lakh as part of its corporate social responsibility (CSR) activities, while a farmers’ action group mobilised the rest. Talks are on to set up such reactors in nearby villages. A couple of industries have also shown interest.

“There can be nothing better than using CSR funds to set up UDMSRs,” says Pravin Rabadia, president, Padra Industries Association, while observing that such reactors are the best investment for the future. Underscoring one of the benefits, Rabadia says it takes just one paise to treat sewage as against the cost of 10 to 12 paise in the conventional STPs. In UDMSRs, sewage in even small quantities could be treated.

Noting that sewage treatment plants have largely been limited to the cities, Prasoon Gargava, Regional Director (Western Region), CPCB, says UDMSR is easy to replicate. “Prima facie, depending on how it works, such cost-effective technologies can be replicated as the operational cost is also low and you do not require highly skilled manpower to operate it.”

Dr Patel thinks that creating awareness and finding funds are the needs of the hour. “In future, underground pipes can be laid to get untreated sewage into the plant and release treated sewage water into the farms,” he says.

According to Prajapati, their focus is to utilise treated sewage water for irrigation. For that, they have been not only educating people of Luna but also villagers in places like Mithi Virdi near Bhavnagar. “People from other villages have started visiting Padra to learn about the plant’s operation." 

Ghanshyam Chandubhai Patel (48) does not have any problem using treated sewage water for irrigation. "This is a small project, so not all are getting the treated water for irrigation. In fact, this treated water is far better than the polluted water that comes from tubewells in the area," he reasons. 101Reporters/SP