Hydrogen sulphide control in sewage collection systems

[Randolph]

I would like to get dosage requirements for the various chemicals used to treat H2S in force mains and trunk sewers.
Chemicals of interest are KMnO4, Mg(OH)2, FeCl2, FeCl3, NaNO3, CaNO3, H2O2, ClO2.

 

[mikolay]

We have used calcium nitrate solution for hydrogen sulfide suppression. US Filter offers this solution by their trade name, Bioxide. They will make dosage calculations for you. Please note that the owner of the sewage collection system may ask you to add more than enough treatment chemical to the "high" end of the collection system so that there is a residual concentration available for downstream consumption. My only complaint about the Bioxide application was the rep underestimated the dosage amount needed. Otherwise it's a fine product that is not hazardous, does not freeze in winter. It's not inexpensive, but it beats relaying large diameter concrete trunk sewer lines.

 

[KARENEUGENIA]

We are investigating a technology for controlling chemical feed by measuring H2S on-line. Is this a technology you would be interested in? Can we contact you for feedback on design requirements?

 

[AtulBhalla]

KARENEUGENIA.......
Yes, we have an interest in knowing how much to dose chemicals in order to either suppress H2S formation or control of pH etc in the scrubbing functions where H2s removal is being attempted.
At this stage I can give only preliminary design requirements, but please feel free to contact me at :
atulbhalla@infl.net

 

[BobPE]

Randolph:

We can't figure out the dosing requirements without flow information and a good understanding of the characteristics of your wastewater. My rule of thumb has been to first understand why you are getting H2S which in your case since you had no flow information would most likely be attributed to low flows on an overdesigned system. Planning on eliminating H2S formation or reducing it would give you such a great understanding of your system that sizing chemical feeds and types of chemicals would become second nature to you form the experience.

The more information you give us the better we can help.

Bob

 

[AtulBhalla]

Randolph: (or whoever is answering.......I get a bit confused about this).....the flow rates for this specific case are given below. However, there are many such systems with somewhat similar capacities, so we are looking for a generic solution to a major problem facing the Indian environmental sector.

Problem:

1. Hydrogen sulphide is to be removed from a continuous biogas stream containing approx. 3% of H2S. Gas flow is approx. 14,000 cu.m / day (min. 7000, max 17,000 cu.m /day) at ambient temperature and approx. 70-100 mm WC. Biogas also contains approx. 65% methane and balance is predominantly carbon dioxide. Cleaned gas is meant to be used for power generation in a combustion ignition / dual fuel gas engine. Cleaned gas should have less than 500 ppm H2S, preferably lower, since the feed gas flow may fluctuate depending upon inflow conditions to the bio-methanation reactors.
2. The initial cost of the gas cleaning system and also its operating and maintenance costs must be low. The costs should be based on plant fabricated, erected and operated in India, under the tropical to semi-tropical conditions prevailing in various parts of the country.

PS: at present there is a simple water wash system in a drum for the biogas to get partially cleaned. Subsequently, the pressure is boosted in a twin lobe compressor(cheap & local make) for conveying the biogas to a boiler. Any equipment required to be installed can be made available, either as bought out or fabricated.
Atul Bhalla

 

[AtulBhalla]

In answer to Randolph's Q of 22 June 2001........u must have got the answer by now but I thought I might share with u that US Peroxide has a fair amount of info on dosing rates...look at their website. comparisons with other chemicals is also listed.