Organic loads, oils and bacteria: requirements and IDRO Group solutions for food wastewater treatment
In the food industry, wastewater treatment requires more targeted solutions than in other sectors, because effluents often combine high organic loads, oils and fats, strong production variability, and a bacterial load that demands strict control. The goal is not only to comply with discharge limits, but also to improve operational continuity, reduce costs and, where possible, enable recovery strategies. In this context, IDRO Group designs and delivers custom industrial wastewater treatment plants, tailored to the discharge matrix and the objectives of the production site.
Food industry wastewater: organic loads, FOG and bacterial content
Wastewater generated by the food industry mainly comes from equipment and line washing, sanitation processes, rinsing and product losses. The main characteristics that make it “critical” and guide its treatment include:
- High and rapidly biodegradable organic load: residues of sugars, starches, proteins and whey can quickly increase oxygen demand and trigger fermentation if water stagnates.
- Suspended and colloidal solids: flours, vegetable fibers, pulps, protein coagulates and micro-particles can increase turbidity and sedimentation, requiring targeted removal to avoid overloading downstream treatments.
- FOG, oils and fats: animal and vegetable fats, emulsions from washing and detergents can cause foaming, odors and clogging, while reducing biological treatment efficiency if not properly separated.
- Bacterial load and microbiological variability: the food matrix and process conditions influence microbial content; in warm periods or with prolonged storage, the risk of degradation and odors increases.
- Flow and concentration variability: production cycles, end-of-shift operations and CIP phases can generate sharp peaks, alternating highly diluted streams with concentrated ones.
- pH and cleaning agents: sanitation and washing introduce alkalinity or acidity and surfactants, affecting process stability and downstream technology selection.
This combination makes a modular and robust treatment line preferable, capable of absorbing peaks and maintaining stable performance over time.
Hygienic requirements and regulations: what impacts design and operation
In the food industry, hygienic requirements do not only concern effluent quality, but also how the wastewater treatment plant is installed and managed, because layout, materials and operating procedures directly affect safety, odors and production continuity.
At the design stage, it is essential to include solutions that limit aerosols and splashes in sensitive areas, for example through proper covers and ventilation, and to reduce stagnation through controlled volumes and retention times, recirculation where needed, and geometries that minimize deposits and fermentation. Likewise, the selection of materials and finishes must consider exposure to detergents and sanitizers as well as corrosion risks, while sludge and by-product handling must be organized with dedicated lines and safe maintenance access to avoid interference with production areas. Where required, air containment and air treatment support odor control; finally, cleanability by design, along with automation and logging of levels, alarms and key parameters, makes it easier to maintain consistent and traceable performance.
From a regulatory perspective, wastewater discharge in Italy is governed by the Legislative Decree 152/2006 (Part III), with limits and requirements that may be further specified by local regulations and discharge permits. Requirements and controls vary depending on the receiving body, for example discharge into public sewer systems versus discharge into surface water bodies, which is why design must be carried out case by case, starting from site-specific authorization conditions.
At IDRO Group, we support this phase by integrating matrix analysis, treatment objectives and discharge constraints to define a consistent and verifiable solution. In practice, water treatment in the food industry must combine removal performance and operational stability with a control and documentation system aligned with applicable site requirements.
Pre-treatment strategies: equalization, oil/grease separation and solids removal
In the food industry, pre-treatment is often the step that determines the stability of the entire treatment line, as it protects downstream processes from typical discontinuities such as end-of-shift peaks and cleaning cycles. The process generally starts with proper equalization, useful for dampening flow and concentration fluctuations and, when necessary, managing pH variations caused by cleaning products. Upstream of biological treatment, targeted removal of solids and FOG is then carried out through screening and filtration to intercept fibers, pulps and coarse residues, along with grit removal where inert materials are present, and dedicated oil and grease separation systems.
When the lipid fraction is high or difficult emulsions are present, a commonly adopted solution is dissolved air flotation (DAF), effective in separating fats, oils and suspended solids with the aid of coagulation and flocculation reagents. In DAF systems, recirculated water is typically saturated at 4–5 bar, and during pressure release at atmospheric conditions, microbubbles form and attach to flocs, lifting them to the surface where they are removed. At IDRO Group, this approach is also applied to concentrated wastewater with high fat and organic loads, with applications across various food sectors such as slaughterhouses, meat processing, dairy, winemaking and confectionery.
A well-designed primary treatment line reduces loads and variability entering biological stages, improves overall efficiency and limits fouling phenomena, especially when membrane technologies are used downstream.
Emerging and established technologies: aerobic, anaerobic and membranes for quality and reuse
For organic load removal, aerobic processes remain a benchmark for reliability and effluent quality, while anaerobic processes are often considered when loads are high and energy costs need to be optimized, with potential biogas recovery where applicable. When the objective also includes more stable and controllable effluent quality, membrane integration can become decisive, enabling advanced physical separation of biomass and better solids management, resulting in clearer and more consistent effluents over time.
Alongside “traditional” technologies, the agri-food sector also adopts targeted treatments for reducing microbiological load at specific process stages. One example is the use of ozone in-line for sterilizing water used in washing vegetables prior to packaging, with generator and mixer integrated into the circuit and the option of open or closed-loop operation for water recirculation.
For example, for a food company in the province of Bergamo, an ozone sterilization system for process water used in washing ready-to-eat vegetables was designed and installed. The solution, with a capacity of 24 m³/h and an indicative ozone dosage of 130 g/h, is aimed at reducing bacterial load during washing and can support controlled water recirculation.
It is important to note that this is not a wastewater treatment stage, but an upstream intervention in the process that can help reduce water consumption and, consequently, the volume of wastewater generated.
Overall, the integration of biological treatment, advanced separation and targeted disinfection represents one of the most established approaches for food industry wastewater treatment focused on compliance, operational stability and water efficiency.
Recovery and sustainability: internal reuse, process greywater and resource recovery
Once treatment is stabilized, many companies evaluate recovery along two axes: water reuse and material or energy recovery. For reuse, the most effective approach is to first define compatible non-potable uses—such as technical washing, plant services and auxiliary utilities—and then design the target quality following a fit-for-purpose approach with a proportionate control system. To enable these scenarios, IDRO Group has also developed modules dedicated to wastewater recovery and reuse, installed downstream of treatment, with sections that can be combined in series or parallel depending on the required quality and recovery rate, and with monitoring of key parameters and alarm management.
Recovery is not only about water. In the food industry, a significant share of benefits comes from upstream prevention: reducing product losses, optimizing detergents and CIP cycles, and separating more concentrated or fat-rich streams before they mix with more diluted wastewater. Where applicable, managing high loads can also enable energy recovery in anaerobic lines and improve sludge management.
Do you want to optimize wastewater treatment in your food processing facility? Contact us: we analyze your discharge matrix, define compliance and recovery goals, and design a tailored solution, with support also for commissioning, maintenance and plant management.
