Executive Summary
What was this pilot project about?
This pilot project demonstrates the use of a modular infiltration ditch system for rainwater harvesting to effectively manage rainwater locally despite sealed surfaces. The system, installed at the pilot site of IIT/ISM University in Dhanbad, serves as an example of an underground rainwater reuse and storage option for urban locations in India. Unlike conventional harvesting systems, the system is not visible and does not require expensive land. Rainwater collected from roof areas is directed to an underground rainwater collection basin with infiltration capability to recharge groundwater and to protect surrounding areas from flooding.
General project profile
Population served (in PE): ~ 50 PE
System capacity: 3-6m3/day
In steady-state operation since 12/2022
Piloted technological system
Input: Raw wastewater (hospital)
Output (s): Treated disinfected effluent
Flow scheme: Sedimentation in storage sump - Moving Bed Biofilm Reactor (MBBR) + Biotower - Aerated Horizontal Flow Constructed Wetland (AHFCW) #1 - Toxidation module (On-site Chlorine Generation OCG + UV) – AHFCW #2
Figure 1. Completed treatment system in Kharagpur with Canna Indica (left wetland bed) and Chrysopogon zizanioides (right wetland bed). Source: OTTER, (2023)
Figure 2: One of the potential treatment train configurations (MBBR; CW1, CW2, disinfection, toxidation. Source: AUTARCON (2023)
| Use of outputs/products: | Reuse of treated effluent in horticulture and in toilets of nearby households |
Location and conditions
The site is located inside of the Kharagpur Subdivisional Hospital. The climate is tropical, and the temperature reaches up to around 45 °C in the summer. There is often rainfall and relatively high groundwater levels in the region, with laterite being the most prevalent soil type in the region. Since this site is located at a hospital, the only nearby settlements are that of hospital staffs and the hospital wards itself.
Project milestones
The following milestones were taken to set up this pilot project:
- Baseline data collection and analysis
- System design
- Permission was obtained from hospital authority to set up the treatment plant in their campus.
- Permission for electricity was obtained via mutual permission from hospital and West Bengal State Electricity Board.
- Permission for fresh water supply was obtained from Public Health Engineering Department, West Bengal.
- Purchase of materials: Many of the required components were available within India. The substrate material for the constructed wetlands, the drip lines for the aeration, and certain parts pertaining to the toxidation module were not available in West Bengal directly. The substrate material, blowers and drip lines were purchased in a different state of India and the parts of the disinfection and toxidation modules were imported from Europe.
- The plants for the wetlands were locally available. The pumps, aerators, and parts related to plumbing were also locally available. The MBBR and the biotower was shipped from Kolkata.
- Construction of the Wetlands, installation of aeration and pipeline system, filling with media and plantation
- Installation of Onsite Chlorine Generation System and Toxidation unit, start-up of such
- The plant was made operational from 11th November 2022
Figure 3: Installation of aeration system. Source: OTTER (2022)
Figure 4: Treatment system after startup of operation. Source: OTTER (2023)
Figure 5: Treatment system after 4 months of operation. Source: MAJUMDER (2023)
Figure 6: Pilot Unit for Onsite Chlorine Generation and Chlorine UV AOP. Source: OTTER (2023)
Who was involved
IIT KGP, Iridra SRL, AUTARCON GmbH, Aarhus University were involved in planning and design of system.
IIT Kharagpur: Setting up of the entire treatment plant, designing of the MBBR units, monitoring the performance of the plant.
AUTARCON: Installation of the aeration systems in the AHFCW and installation of the toxidation module and monitoring of the performance of the plant.
JRMS Engineering: Construction and fabrication of the treatment units (MBBR and AHFCW)
Kharagpur Subdivisional Hospital: Providing permission to us for carrying out the work.
As general observations concerning the involvement of the different parties in the project implementation process, the following aspects are notable: the design of system like the presented one, requires specialised manpower. The design of the AHFCW was carried out by IRIDRA, the design of the MBBR and biotower was carried out by IIT KGP, and the design of the onsite chlorine generation unit and the Toxidation module was carried out by experts from AUTARCON. Construction and installation was carried out by JRMS Engineering Works, a Kolkata-based company. Four to five workmen were required for the construction of the wetlands, fitting the aeration lines, filling of the wetland systems and plantation of the beds. Installation of the Toxidation unit was carried out by AUTARCON. Finding skilled and ambitious labour for both the construction and operation phase turned out as a challenge.
Set-up of operation and maintenance phase
The daily operation of the plant is carried out by a single operator that was trained on-site. The daily operations of the plant including switching on and off the pumps, aerators, and cleaning of choked pipe lines are carried out by the operator employed at the site. Supervision of operations, as well as taking and analysing samples is carried out by the teams from AUTARCON and IITKGP.
Operational experience and performance
In general terms it can be stated the operation up to the time this case study was compiled) has been smooth and hassle free.
The most common operational problem, the clogging of inlet pipe leading to the interruption of flow, can easily be tackled by the operator and the collection sump is large enough to cover clogging periods.
The analysis of the wastewater samples are carried out by the research scholars of Prof. Gupta.
Below some of the most prominent observations made during operation of the plant so far:
- Treatment was carried out in 3 phases: conditions Phase (1) MBBR+ CW1 (Continuous Aeration) + Toxidation Unit + CW2 (Continuous Aeration), Phase (2) CW1 (Continuous Aeration) + Toxidation Unit + CW2 (Continuous Aeration), and Phase (3) CW1 (Intermittent Aeration) + Toxidation Unit + CW2 (Continuous Aeration)
- High degree of COD and turbidity removal was observed
- High ammonia removal was observed, and the ammonia was converted to nitrate
- The system has also shown effective performance in terms of fluctuations in COD and TSS concentrations.
- The toxidation module was effective in bringing down the solids concentration and turbidity
- However, low Carbamazepine removal was observed even after the toxidation module. This area needs further research.
Based on the final COD, TSS, and turbidity concentrations, the treated water easily satisfies the discharge standards and may be used in restricted agricultural reuse, and agriculture of processed and non-food crops (USEPA, 2012).
Type of reuse and RRR considerations
The initially intended reuse for the effluent of this treatment system was irrigation in horticulture and the use as toilet flushing water. Even though, from a technical perspective, the system does perform well enough to safeguard required qualities for certain reuses (see above), practicing reuse was limited by …. At present the system is treating 3000 ± 500 L/day of wastewater. However, as per the hospital authorities, they need the treated water e.g. for toilet flush. Furthermore, the amount of water treated is very limited The hospital authorities seemed reluctant regarding using the wastewater for any beneficial purposes and they are under the impression that it is a side project of IIT, and they have nothing to benefit from it. Also, the people around the area, they are not much knowledgeable about the technology, and they are creating nuisance around the treatment plant area. Taking all these things into considerations, reusing the treated water may not be a thing that we can implement soon.