One of India’s leading power generation companies used to rely more on traditional water
treatment tools for boiler feed water treatment. So, the system and setup were developed by that. The company’s power generation setup in South India had tried reverse osmosis + EDI
treatment on boiler feed water for the first time. Within the first few months, they started facing a
problem of a rise in feed pressure and high differential pressure. Frequent cleaning was supportive
in controlling the condition up to a certain limit, but again, the trend of rise in feed pressure was maintained.
After a few cleaning cycles, deterioration of product quality and quantity was also observed. This all
actions, and costly downtime and replacement cost of membrane turn up to the panic situation.
We received the call for an autopsy from this OEM. Based on our recommendation, they have selected the
RO membrane for autopsy and sent it to us with recommended packing. We studied this case and came up
with very interesting facts.
So, let’s see the case and its findings. The principal effluent treatment is as follows :
Chemicals used for Raw water treatment :
1 . Chlorine
2. Ferric Chloride
Chemical used for RO feed treatment :
1. SMBS
2. Antiscalant
After receipt of the membrane while carrying out the autopsy, we came up with very valuable observations
and findings as follows :
1. Aberration / Erosion observed
2. Delamination of the polyamide layer observed
The above observation reveals some condition, and understanding of an exact interpretation of the same is required. Some of our analytical findings and interpretation of foulants deposited on the membrane leaf are as follows:
1. In chemical analysis, silica deposition was prominently observed, followed by iron.
2. There was very little microbial deposition.
3. The Fujiwara test and the Dye test were positive at various locations.
4. The spiking of colloidal silica, which has not been highlighted in routine analysis, was the major culprit.
Sharp crystals of silica have scratched and eroded the membrane while CIP.
5. Uncontrolled or excessive dose of ferric chloride has reflected in terms of deposition on a membrane
sheet, which reacts as a catalyst for oxidation of the membrane.
6. Inadequate doses of SMBS or high spiking of chlorine doses have oxidised the membrane.
Although the power generation company is confident, well acquainted with water chemistry, they were
using the traditional demineralisation technique for water purification/treatment. Analysis of colloidal
silica was missing in their monitoring plan and also in the raw water treatment laboratory.
Vipanan Analytical Technologies LLP Lab: Flat 1-2, Nilay, Plot No. 23, Prathamesh Park, Baner, Balewadi Road, Baner, Pune 45
Email: lab@vipananlab.com
Tel no: 8149036220 /8793046221
Web: www.vipanan.co