Wastewater Treatment Project for a Cosmetics Manufacturing Enterprise

I. Project Overview

This case is a wastewater treatment renovation project for a small and medium-sized cosmetics manufacturer in South China. The company mainly produces and packages creams, lotions, toners, and personal care daily chemical products. The production process does not involve high-temperature or heavily polluting procedures. Wastewater mainly comes from production equipment cleaning, workshop floor washing, residual liquid from raw material preparation, laboratory testing wastewater, and concentrated water from pure water preparation, and does not contain wastewater with heavy metals or toxic and harmful raw material residues.

The designed wastewater treatment capacity of the project is 150 m³/d, with an average actual daily discharge of 120-140 m³. Wastewater discharge shall comply with the Tier 3 standard of the Second Period of the Guangdong Province Discharge Limits for Water Pollutants (DB44/26-2001). After treatment meets the standard, it is connected to the municipal sewage pipe network and discharged to the urban wastewater treatment plant for advanced treatment. The project is equipped with an integrated wastewater treatment station covering an area of 80 ㎡, achieving fully automatic intelligent operation with simple operation and maintenance, and is suitable for the characteristics of small and medium-sized cosmetics enterprises, such as large fluctuations in production conditions and unstable water quality.

II. Wastewater Quality Characteristics and Influent/Effluent Indicators

1. Core Characteristics of Wastewater

Cosmetics production wastewater is a typical type of wastewater with low toxicity, high organic matter, high surfactants, and high emulsification, and its water quality fluctuates strongly: during peak production periods, cleaning wastewater is discharged in a concentrated manner, and the concentrations of COD and surfactants rise significantly; during shutdown periods, wastewater discharge drops sharply and the water quality is relatively clear. The wastewater contains oils, emulsifiers, humectants, fragrances, colloids, and other substances. The water body is turbid, prone to foaming, has moderate biodegradability, and contains a relatively high level of suspended solids. If directly subjected to biological treatment, it can easily cause sludge bulking and system breakdown, so demulsification pretreatment must be carried out first.

2. Designed Influent and Effluent Water Quality Indicators

III. Core Treatment Process Plan

Considering the characteristics of cosmetic wastewater—severe emulsification, highly fluctuating organic matter, and a large amount of surfactants—this project adopts a combined process of pretreatment demulsification + Fenton advanced oxidation + biochemical treatment + advanced sedimentation. This avoids the problems of poor treatment efficiency, easy foaming, and sludge loss associated with using a single biochemical process to treat emulsified wastewater. The overall process is mature, has low operation and maintenance costs, and is suitable for small to medium water volume conditions.

Process Flow: Wastewater Collection Tank → Bar Screen → Equalization Tank → Acid-Base Neutralization Demulsification Tank → Fenton Oxidation Tank → Coagulation Sedimentation Tank → Hydrolysis Acidification Tank → SBR Biochemical Tank → Final Sedimentation Tank → Compliant Discharge

1. Pretreatment System (Demulsification + Homogenization Adjustment)

Production wastewater is uniformly collected through the workshop pipe network. It first passes through a mechanical screen to remove large-particle impurities such as hair, raw material residues, and floating debris, preventing subsequent equipment blockage. The wastewater flows by gravity into the equalization tank, effectively balancing water quality and quantity and mitigating fluctuations caused by intermittent production discharge. An aeration mixing device is installed in the tank to prevent suspended solids from settling and accumulating, while also preliminarily degrading some volatile organic compounds.

The effluent from the equalization tank enters the neutralization and demulsification tank, where acid-base regulators are dosed to adjust the wastewater pH to 7-8. At the same time, a demulsifier is added to break the emulsified stable structure of oils and surfactants in the water, destabilizing and coagulating colloidal particles and suspended oils to achieve preliminary oil-water separation. This greatly reduces the load on the subsequent biological system and solves the wastewater foaming problem.

2. Advanced Oxidation System (Fenton Process)

The demulsified wastewater enters the Fenton oxidation tank, which uses an Fe²⁺+H₂O₂ Fenton reagent system. Utilizing the strong oxidizing power of hydroxyl radicals, it efficiently degrades pollutants in cosmetics wastewater that are difficult to biodegrade, such as high-molecular-weight organic matter, residual fragrances, and surfactants, breaking down refractory macromolecular groups and greatly improving wastewater biodegradability. This system controls the hydraulic retention time at 2h and strictly regulates the reagent ratio and reaction pH to ensure oxidation efficiency, effectively solving the treatment challenges of high-COD, high-LAS wastewater.

3. Coagulation and Sedimentation System

The Fenton oxidation effluent enters the coagulation and sedimentation tank, where polyaluminum chloride (PAC) and polyacrylamide (PAM) are dosed in sequence. This causes the fine suspended solids and colloidal impurities after oxidative decomposition to coagulate into large flocs, which are rapidly separated by gravity sedimentation. This further removes residual organic matter, suspended solids, and metal ions from the water, reduces effluent turbidity, and provides stable influent quality for subsequent biological treatment. Sludge at the bottom of the sedimentation tank is regularly discharged into the sludge thickening tank for unified dewatering and disposal.

4. Biological Treatment System (Hydrolysis-Acidification + SBR)

The coagulation and sedimentation effluent flows by gravity into the hydrolysis-acidification tank. Under the action of anaerobic microorganisms, macromolecular and refractory organic matter in the wastewater is hydrolyzed into small-molecule organic acids and alcohols, further improving wastewater biodegradability while degrading part of the COD and buffering the impact of water quality fluctuations on the subsequent aerobic system.

A sequencing batch reactor (SBR) activated sludge process is subsequently adopted, integrating aeration, sedimentation, and decanting functions without the need for an independent secondary clarifier, featuring a small footprint and strong resistance to shock loads. Through the metabolic action of aerobic microorganisms, pollutants such as BOD, COD, and ammonia nitrogen in the water are thoroughly degraded. The system sludge concentration is controlled at around 5500mg/L, with a hydraulic retention time of 3h, adapting to the fluctuating water quality conditions of cosmetics wastewater with stable treatment results.

5. Deep Sedimentation and Discharge System

SBR biochemical effluent enters the final sedimentation tank to further settle residual activated sludge and fine suspended solids, ensuring clear and stable effluent. All indicators of the final sedimentation tank effluent stably meet standards and are discharged into the municipal sewage network through a standardized discharge outlet. The excess sludge and settled sludge generated by the system are uniformly collected into the sludge thickening tank. After dewatering by a screw press dehydrator, the sludge cake is entrusted to a qualified unit for compliant disposal, and the filtrate is returned to the regulating tank for reprocessing, with no wastewater discharged or wasted.

IV. Project Operating Parameters and Results

1. Core Operating Parameters

• Designed treatment capacity: 150m³/d, actual operating capacity: 120-140m³/d

• Fenton reaction pH: 3-4, reagent ratio: ferrous sulfate:hydrogen peroxide = 1:2.5

• Hydraulic retention time of hydrolysis-acidification tank: 6h, hydraulic retention time of SBR biochemical tank: 3h

• Overall hydraulic retention time of the system: 18h

• Sludge return ratio: 50%, reagent dosage stable and controllable

2. Actual Operating Results

After the project was put into operation, the system ran stably with strong resistance to shock loads, adapting to the company's operating conditions of round-the-clock production and intermittent discharge, with effluent quality meeting standards consistently throughout the year. According to third-party testing, the effluent COD remained stable at 320-420mg/L, LAS at ≤15mg/L, SS at ≤180mg/L, and pH maintained at 6.5-8.5, fully meeting the standards for connection to the municipal pipe network, with no excessive discharge or environmental complaints.

At the same time, the system effectively solved the industry pain points of cosmetic wastewater being prone to foaming, sludge bulking, and unstable treatment results. The equipment has a high degree of automation, requires no dedicated 24-hour staffing, and is simple to operate and maintain on a daily basis.

V. Investment and Operating Cost Analysis

1. Project Investment

The overall project investment is 480,000 yuan, including integrated wastewater treatment equipment, chemical dosing system, automatic control system, sludge treatment equipment, pipe network renovation, and installation and commissioning costs. Compared with traditional split-type wastewater treatment processes, it saves 40% of floor space and shortens the construction period by half.

2. Operating Cost

The comprehensive operating cost is 2.6 yuan/ton of water, including electricity, chemicals, operation and maintenance labor, and sludge disposal costs, which is lower than the industry average operating cost and offers significant economic advantages. It can reduce COD pollutants by about 12.5 tons per year, greatly reducing the company's environmental discharge pressure and meeting environmental inspection and green production requirements.

VI. Project Process Advantages and Summary

1. Core Process Advantages

• Highly targeted: Through demulsification + Fenton pretreatment, it precisely solves the core problems of cosmetic wastewater such as high emulsification, high surfactant content, and poor biodegradability, avoiding paralysis of the biological treatment system

• High stability: A combined process of pretreatment + advanced oxidation + biological treatment enables multi-stage degradation of pollutants, with strong resistance to fluctuations in water quality and volume, making it suitable for the variable production conditions of small and medium-sized enterprises.

• Easy operation and maintenance: A fully automated control system with automatic dosing, automatic aeration, and automatic drainage requires no dedicated on-site staff, reducing labor costs.

• Compact footprint: An integrated design with modular layout occupies minimal space, making it suitable for sites with limited plant space.

2. Project Summary

This project targets the characteristics of wastewater from small and medium-sized cosmetics enterprises, which is complex in quality, highly variable, and contains large amounts of emulsified organic matter. It adopts a combined treatment process, abandoning the shortcomings of a single biological process. Through pretreatment demulsification to remove emulsified pollutants, Fenton oxidation to degrade refractory organic matter, and deep purification by the biological system, the wastewater is discharged stably and in compliance with standards. The project features low investment, controllable operating costs, and simple operation and maintenance, perfectly matching the environmental governance needs of small and medium-sized cosmetics manufacturers. It can provide a mature and replicable engineering reference for the treatment of similar wastewater from daily chemical and cosmetics production.