Location: India
Product: External MBR System
Capacity: 2,500 m3/day
COD feed: 2,000 – 3,000 ppm
Membrane: 8 mm PVDF, non-backwashable
The volume of wastewater effluent generated by the 130+ member tanneries made it necessary to install an energyefficient system to enable wastewater reuse and lower discharge. Due to the high fouling and poor cleaning efficiency of the external aerated UF system, the overall recovery was far below the original design specifications, producing a permeate flux of only 28 – 30 LMH and requiring backwashing of the system every seven minutes.
Membrane plugging was also a recurring problem that required weekly shutdowns to clean the UF trains. Plant operators needed a robust MBR system to increase the recovery of the reverse osmosis (RO) unit at the end of the process which then fed treated permeate back into the tanneries for reuse. As in many wastewater/effluent treatment plants, MBR systems are typically employed as a pre-treatment step for RO units to provide better feed quality, thereby increasing RO system recovery and reducing the scaling potential within the RO unit.
Given the heavy volume of hairs and fibers in the feed stream, clogging was a serious ongoing problem for plant operators. To resolve this, Berghof Membranes engineers designed the external MBR system so that plant operators can easily reverse the direction of the system’s flow: top-to-bottom or bottom-to-top. This helps to prevent the accumulation hairs and fibers that would otherwise settle in the membrane tubes.
The external MBR system was designed to be a vital part of a robust zero liquid discharge (ZLD) process that minimizes the footprint of an otherwise discharge-heavy industry.
| System Performance | |
|---|---|
| COD Effluent | < 300 ppm (90 % COD removal) |
| Velocity | 3.5 m/s |
| System Flux | 90 LMH |
| Membrane Surface | 1282 m2 |
| System Configuration | 4 loops, 24 total modules (doubled in 2019) |
A basic process flow diagram (PFD) of the plant is shown in Figure 1 (see below). In this process, the raw effluent from the tanneries is directed through a rotoscreen to remove solids larger than 1 mm. The feed is then sent to a homogenization tank outfitted with a mixing system that homogenizes all the various streams from the 130+ tanneries.
The wastewater is then pumped to flocculation and coagulation chambers before it flows to a circular clarifier that precipitates metals and colloidal solids. To remove the bulk of the hairs and fibers present in the wastewater stream, the feed passes through a 250 – 350 micron filtration system before it is pumped into the MBR tank equipped with a jet aeration system.
The external MBR sytem from Berghof Membranes was designed to consists of 4 loops with 6 modules each. The modules contain 8 mm diameter membrane tubes perfectly suited for high solid concentrations. The ability to reverse the direction of the flow within the system (top-to-bottom or bottom-to-top) ensures that the accumulation of hairs and fibers within the tubes is minimized.
This MBR system design provides a high quality permeate stream that is then sent to a reverse osmosis (RO) unit for further treatment and the RO permeate is reused back into the tanneries. The RO concentrate, on the other hand, is sent to a multiple-effect evaporator (MEE).
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