Blaydon Dairies doses Nutriox to combat Odour and Hydrogen Sulphide gas accumulation

(2008-01-07) Receiving regular odour complaints from surrounding business and facing increasing pressure from the EA to find a solution, Blaydon Dairies had to work quickly to identify and eliminate the problem.

Upon recommendation from an outside consultant, Rose Hotten - Site Manager contacted Yara and an initial meeting was arranged with a site tour and survey.

From this, spot samples concluded that:

• Excellent COD reduction through DAF, BioTower1 and BioTower2
• Key Bioactivity is in BioTower1
• Sulphide measured at 16 mg/l after Bio Tower 1
• Recirculation promoting SRBs in BioTower1
• Black material throughout plant

The site was dosing a product without adequate technical support which was proving to be ineffective.

From this, both parties agreed, to dose Nutriox to inlet of BioTower1 at an initial dose rate of 15 l/hr.

Dosing began, with Geoff McCaughtrie - Yara Technical on-site to carry out spot samples. Geoff explains, "after 2 hours sulphide was < 0.25mg/l with the black material gone. The samples also found that there was high nitrate after Bio Tower 1 which prompted me to reduce dosage to 7.2 litres / hour. An odalog was also inserted post Bio Tower 1."

A follow-up visit a fortnight later, concluded that a reduction to the dosage was acceptable to 5.8 l/hr and spot samples found a sulphide level of 1.6mg/l.

Blaydon was happy as odour had disappeared and no complaints had been received. Data downloaded from the odalogger had shown that the H₂ S was controlled at 1 ppm however there was the odd peak at 5 ppm, which if left untreated would cause complaints. In view of this the dosing pump was increased to 10.5 l/hr.

The occasional peak of 5ppm was recorded which would lead to complaints if left untreated.

Further to a meeting with the customer to explain our findings it was agreed that Yara had successfully proved that Nutriox had worked and that we should look to dose via one of our controllers. This would ensure that the Nutriox is dosed as and when required.

However, the odalog data from the optimisation visit showed that the site is still experiencing peaks:

Rose Hotten, confirms, "To date the site is dosing Nutriox at 15 litres / hour with the occasional odd peak. Complaints have ceased, however, by adopting this fixed dosing regime, the site tends to overdose with Nutriox which does lead to excess nitrates in the system.  To prevent this, a proposal for an IDA Controller has been forwarded by Yara, which we are looking to implement; as this is the best way forward to have controlled dosing to hit any unexpected peaks in the system and to prevent overdosing".

Manesh Patel, Account Manager for Blaydon, concluded, "Yara was quick to react and very proactive in trying to find a solution for the customer. With good support from our Technical team, we were able to demonstrate the effectiveness of Nutriox within a short timescale."