Control of anaerobic wastewater treatment

Abstract

A method of controlling wastewater treatment in multi step system comprising at least one anaerobic step and at least one carbon dioxide stripping step by a combination of (1) recuperable abiotic species and carbon dioxide stripping, wherein the recuperable species can be metal ions such as calcium and iron, the said species are charged in the treatment system and form soluble carbonates maintaining the carbonic acid equilibrium and pH in anaerobic process steps and recuperated and retained in the system as insoluble carbonates or hydroxides formed in the carbon dioxide stripping step, and (2) conditioning the sludge by cultivating methanogens in the sludge in a dedicated process zone called sludge conditioner, and recycling the conditioned sludge in the reactor, wherein the volatile fatty acids are rapidly consumed by thus provided methanogens. Dramatic reduction in reagent requirements for pH and other purposes is achieved. The system can be controlled using excess reagent content and excess conditioned sludge supply. In extreme situations, simple automatic control can be used. The process can be automated using a differential pH metering, wherein one pH meter is reading pH in the carbon dioxide stripping reactor, and another pH meter measures pH in a portion of water with carbon dioxide stripped. The level of pH in a water portion with depleted carbon dioxide indicates whether carbon dioxide needs to be additionally stripped or the recycle rate from the stripping step should be increased, and/or the conditioned sludge recycle needs to be increased.

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