Rubber stamp for Zeon effluent upgrade

ACWa Services Ltd has been awarded a £1.2m turnkey design and build contract from latex manufacturer Zeon Chemicals Europe Ltd to extend the company's effluent treatment system at Sully, South Wales. ACWa's site treatability study demonstrated that a 50-60 per cent reduction in the Chemical Oxygen Demand (COD) of the latex was possible, with the installation of an activated sludge system, modifications to the existing feed supply equipment and dissolved air flotation (DAF) system.

Research study

The new system comprises a fully automated secondary treatment activated sludge

system including aeration, degassing, settlement and sludge dewatering stages.

This system is fed with effluent from Zeon’s existing primary treatment DAF

system. The chemical dosing associated with the DAF system is to be fully automated

as part of the contract in order to improve the operating efficiency of primary

treatment. Also, the feed flow-balancing capacity is to be increased in order

to provide a homogenous feed to the DAF system. Combined primary and secondary

sludge produced is to be stored in a sludge holding tank and a belt press is

then utilised to dewater the sludge (see diagram).

In order to optimise the operation of the existing DAF system, ACWa has implemented

various recommendations from the treatability study, including the conversion

of the existing small balance tank to a calamity tank, with the raw effluent

diverted when pH, flow or load are beyond design parameters. Feed pumps have

been installed with inverter drives to allow flow control into the DAF system.

The modifications will provide controlled and average flow to aerobic secondary

treatment, thereby improving operating efficiency and optimising effluent discharge


Automatic monitoring of the final treated final effluent will be undertaken

in a new treated effluent collection tank. Suspended solids and pH monitors

are included and an automatic sampler will provide daily composite sampling

of the treated effluent for routine analysis. Treated effluent transfer pumps

are used to discharge effluent to the existing lagoon.

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