# Fermentation Heating Tube Anti-Corrosion Waste Liquid Treatment & Secondary Corrosion Prevention Specification ## Preface This specification is a supporting document of the complete anti-corrosion document system from Doc.33 to Doc.118. It standardizes classified collection, neutralization treatment, discharge testing, pipeline flushing and waste storage management for pickling waste liquid, alkaline cleaning waste liquid, ion-rich drainage and contaminated flushing wastewater generated in all heating tube anti-corrosion operations. It prevents residual corrosive waste liquid from backflow, sediment deposition and pipeline inner/outer wall secondary corrosion, and unifies environmental protection and equipment dual protection standards for waste liquid links. ## 1. Classification of Corrosive Waste Liquid & Independent Collection Rules Three types of waste liquid are separated with fully independent closed collection pipelines, mixed drainage is strictly prohibited: 1. Acid waste liquid: Dilute hydrochloric acid, citric acid, phosphoric acid pickling drainage, rich in metal ion corrosion products; dedicated acid-resistant collection tanks and delivery pumps shall be equipped. 2. Alkaline waste liquid: Sodium hydroxide, alkaline degreasing and biofilm stripping waste liquid, high organic and protein content; isolated from acid waste storage area to avoid violent neutralization reaction and local heat-induced pipeline corrosion. 3. Medium-contaminated flushing wastewater: Residual fermentation broth, high-chloride circulating drainage, low acid-base concentration but high corrosive ion content; stored separately for preliminary sedimentation before centralized treatment. All collection branch pipes are designed without dead legs, with a self-draining slope layout per Doc.113. After each waste liquid discharge, the pipeline must be rinsed with pure water to eliminate residual corrosive liquid film adhering to pipe walls. ## 2. Standard Neutralization & Treatment Operating Procedures 1. Acid-base mutual neutralization: Transfer acid and alkaline waste liquid into the integrated treatment tank in proportion, continuously stir and monitor real-time pH online instruments per Doc.114, adjust dosage until the pH value reaches the safe discharge range. 2. Heavy metal sedimentation treatment: Add dedicated precipitant for waste liquid containing dissolved titanium, stainless steel metal ions, fully react and filter solid corrosion sediment; sludge is separately sealed for industrial solid waste disposal. 3. High-chloride waste liquid dilution: For drainage with excessive chloride ion concentration, add pure water for gradient dilution before neutralization to avoid chloride enrichment causing pitting corrosion of subsequent public drainage pipelines. All treatment operations must be carried out in the chemical isolation zone specified in Doc.112, with anti-corrosion protective equipment worn by operators, and leakage collecting trays laid under storage tanks to prevent ground and equipment surface corrosion caused by overflow. ## 3. Discharge Detection & Secondary Corrosion Risk Judgment Before any treated waste liquid is discharged into the factory public drainage system, sampling inspection is mandatory: test pH, chloride ion concentration and residual organic carbon content according to the laboratory standards of Doc.115. - Qualified discharge: All indicators meet the threshold, record sampling data and complete discharge; - Unqualified discharge: Stop drainage immediately, extend neutralization or dilution cycle, re-sample and test until up to standard. Key secondary corrosion early warning signals: public pipeline outer wall fogging, drainage pipe welding seam pitting, frequent pH abnormal fluctuation of discharged liquid. Once discovered, suspend all anti-corrosion cleaning work of the corresponding production line, thoroughly flush the whole waste liquid collection system and check for hidden backflow points. ## 4. Waste Liquid System Routine Maintenance & Periodic Inspection Weekly patrol inspection items for waste liquid pipelines and storage tanks: inner wall corrosion spot check, sealing gasket aging, pump body residual sediment accumulation, blind pipe stagnant waste liquid residue. Monthly full circulation cleaning of the entire waste collection loop: alternate weak acid and alkaline circulating flushing to remove metal sediment and biofilm attached to the pipe wall in accordance with Doc.117. Semi-annual wall thickness measurement of acid-resistant storage tanks and waste delivery pipelines; severely corroded lining and pipe bodies are listed for replacement in combination with the service life assessment rules of Doc.110. ## 5. Abnormal Waste Liquid Accident Disposal In case of waste liquid overflow, pipeline rupture or backflow into heating tube main loops: 1. Immediately close all waste liquid discharge valves, cut off the liquid source, use neutralization absorbent to clean leaked corrosive liquid, and isolate contaminated equipment; 2. For heating tubes polluted by backflow waste liquid, carry out full-loop repeated pure water flushing + enhanced passivation treatment, sampling to confirm no residual corrosive ions; 3. Complete accident investigation within 24 hours, analyze root causes such as unreasonable pipeline layout, untimely maintenance or irregular operation, formulate rectification plans and track acceptance results. ## 6. Archive Management Waste liquid collection shift logs, neutralization treatment operation records, discharge sampling test reports, waste pipeline maintenance checklists and overflow accident disposal files implement dual electronic and paper backup archiving. Monthly data statistics analyze the correlation between waste liquid treatment quality and heating tube corrosion failure rate; if secondary corrosion frequently occurs due to unqualified drainage, the waste liquid process parameters and operation clauses will be revised at the quarterly system review meeting. This specification fills the management gap of corrosive waste liquid links in the anti-corrosion system, cuts off the secondary corrosion source outside the main heating circulation loop, realizes simultaneous control of fermentation heating tube protection and factory environmental compliance, and completes the full-flow closed-loop anti-corrosion management system.
