Wastewater Treatment in Food Manufacturing
Industrial wastewater treatment is the process of cleaning water used in factories so it's safe to release or reuse. It usually happens in three stages: primary, secondary and tertiary. In Malaysia, factories must meet discharge limits under the Environmental Quality (Industrial Effluent) Regulations 2009. At Ajinomoto Malaysia, our treated effluent stayed well inside Standard A limits in 2026.
Key Takeaways
- Industrial wastewater treatment removes solids, organic matter, nutrients and germs from factory water before it's released or reused.
- Food factory wastewater is high in organic matter, so BOD and COD are the numbers to watch.
- Treatment runs in three stages. Primary settles out solids, secondary uses microbes to eat organic matter, and tertiary polishes and disinfects the water.
- Malaysian factories must meet Standard A or Standard B limits, depending on whether they discharge upstream of a drinking water intake.
- Since the 2024 amendments to the Environmental Quality Act, polluting can bring fines of up to RM10 million and jail time.
- In 2026, Ajinomoto Malaysia's treated effluent had a COD of 34.3 mg/L against an 80 mg/L limit, with 100% compliance.
What Industrial Wastewater Treatment Is
Factories use water to wash equipment, cool machines, clean floors and make products. Once used, that water carries whatever it picked up along the way. Industrial wastewater treatment cleans it to a standard the law allows before it goes into a river or back into the plant.
It's different from treating household sewage. Industrial wastewater changes a lot from one factory to the next, so each plant needs a system built for its own waste.
| Industrial wastewater | Domestic sewage | |
| Comes from | Factories and processing plants | Homes, offices, toilets and kitchens |
| What's in it | Depends on the industry: organic matter, oils, chemicals, metals | Mostly human waste, food scraps and detergents |
| Treated by | The factory's own Industrial Effluent Treatment System (IETS) | Public sewage treatment plants |
| Malaysian rules | Environmental Quality (Industrial Effluent) Regulations 2009 | Environmental Quality (Sewage) Regulations 2009 |
What's in Food Manufacturing Wastewater
Food factories don't usually produce toxic chemical waste. Their problem is volume. Food industry wastewater is mostly biodegradable, but that same organic load pushes up BOD, COD and suspended solids, according to a 2025 review in the journal Processes. It notes that food wastewater is often non-toxic. Too much organic matter starves rivers of oxygen, because the microbes breaking it down use up the oxygen fish need.
These are the main things treatment plants measure:
| Parameter | What it measures | Why it matters |
| BOD (Biochemical Oxygen Demand) | Oxygen that microbes use to break down organic matter | High BOD drains oxygen from rivers |
| COD (Chemical Oxygen Demand) | Oxygen needed to break down organic matter chemically | A faster, broader check on total pollution |
| TSS (Total Suspended Solids) | Solid particles floating in the water | Makes water cloudy and smothers riverbeds |
| Oil and grease | Fats and oils from cooking and cleaning | Forms a film on water and clogs pipes |
| Ammoniacal nitrogen | Ammonia from protein breakdown | Toxic to fish and feeds algae |
| Colour | How strongly the water is tinted | Blocks sunlight for water plants |
Industrial Wastewater Treatment Process
Most plants treat wastewater in three stages, each removing what the stage before it couldn't. Here's how they compare.
| Stage | How it works | What it removes |
| Primary | Screens and settling tanks | About 60% of suspended solids and 35% of BOD |
| Secondary | Microbes break down organic matter | More than 85% of BOD and suspended solids |
| Tertiary | Filtration, nutrient removal, disinfection | Remaining solids, nitrogen, phosphorus and germs |
Primary Wastewater Treatment
Wastewater first passes through screens that catch large debris. It then flows slowly through settling tanks, where gravity pulls heavier solids to the bottom and lighter oils float to the top. Primary treatment removes about 60% of total suspended solids and about 35% of BOD, but dissolved pollutants pass straight through. That's the job of the next stage.
Secondary Wastewater Treatment
Secondary treatment is biological. The most common method is activated sludge: air is pumped into large tanks so bacteria can feed on the dissolved organic matter. The sludge then settles in a clarifier, and some of it goes back into the tank to keep the bacteria working. Secondary treatment removes more than 85% of both suspended solids and BOD.
For food factories, this is the most important stage, because most of their pollution is organic.
Tertiary Wastewater Treatment
Tertiary treatment polishes the water before it leaves the plant. It can include
- Filters that remove the last suspended solids and BOD.
- Chemical precipitation to take out phosphorus.
- Nitrification-denitrification, where bacteria turn ammonia into harmless nitrogen gas.
- Disinfection with chlorine or UV light to kill any remaining germs.
Tertiary processes can remove more than 99% of the impurities in sewage.
Membrane Bioreactors
A membrane bioreactor (MBR) combines secondary treatment with very fine filtration. Instead of waiting for sludge to settle, the water is pulled through membranes that hold the solids back. The US Environmental Protection Agency says the membranes can replace the secondary clarifier and sand filters in a standard activated sludge system. The result is cleaner water from a smaller footprint, which suits factories with limited space.
Handling the Sludge
Every treatment stage leaves behind sludge, a thick mix of solids and microbes. It has to be thickened, dewatered and then disposed of or reused. Food factory sludge is mostly organic, so it can often go back to the land as fertiliser instead of into a landfill.
Industrial Effluent Rules in Malaysia
The Department of Environment (DOE), under the Ministry of Natural Resources and Environmental Sustainability, regulates industrial wastewater. The main rulebook is the Environmental Quality (Industrial Effluent) Regulations 2009, which sets the maximum pollution a factory may discharge.
Standard A vs. Standard B
Which limits apply depends on where a factory discharges. Standard A is the stricter one. It covers catchment areas upstream of water supply intakes used for drinking water. Standard B covers all other inland and Malaysian waters.
| Parameter | Standard A | Standard B |
| BOD at 20°C | 20 mg/L | 50 mg/L |
| COD (other industries, incl. food) | 80 mg/L | 200 mg/L |
| Suspended solids | 50 mg/L | 100 mg/L |
| Oil and grease | 1.0 mg/L | 10 mg/L |
| Ammoniacal nitrogen | 10 mg/L | 20 mg/L |
| pH | 6.0–9.0 | 5.5–9.0 |
| Colour | 100 ADMI | 200 ADMI |
Competent Persons and Penalties
Factories can't leave their treatment systems unattended. The regulations say an IETS must be supervised by a competent person certified by the DOE's Director General, who must be on duty whenever the system runs. Operators qualify through courses such as CePIETSO, offered through EiMAS, the DOE's training institute.
Getting it wrong has become more expensive. The 2024 amendments to the Environmental Quality Act raised the maximum fine from RM100,000 to RM10 million and brought in mandatory jail terms of up to five years for environmental offences.
Risks of Not Treating Industrial Wastewater
Skipping treatment doesn't make the pollution disappear. It moves the cost onto people, rivers and the economy.
Impact on Human Health
Untreated wastewater can carry bacteria, viruses and parasites. When it reaches rivers used for drinking, bathing or fishing, people risk waterborne diseases. The World Health Organization links contaminated water to cholera, diarrhoea, dysentery, hepatitis A and typhoid. That's exactly why Standard A is strictest for discharges upstream of water supply intakes.
| Waterborne Diseases | Pathogens spread through contaminated water, causing illnesses. |
| Toxicity | Harmful pollutants can lead to respiratory, skin issues, and cancer. |
| Nutrient Pollution | Excessive nutrients cause harmful algae blooms and unsafe water. |
Impact on the Environment
Nutrients in wastewater feed algae. According to the US EPA, excess nitrogen and phosphorus cause algae to grow out of control. When the algae die and decompose, they use up the oxygen in the water, and fish and other aquatic life can't survive. Untreated effluent can also seep into soil and groundwater.
| Water Pollution | Discharging wastewater pollutes water bodies, harming aquatic life. |
| Groundwater Contamination | Polluted wastewater infiltrates and contaminates groundwater. |
| Ecosystem Damage | Untreated waste disrupts ecosystems, harming plants and animals. |
Impact on the Economy
Polluted water costs money to fix. Public funds go to cleaning rivers and treating illness, water treatment plants may have to shut down, and fishing and tourism lose income. For the factory itself, fines of up to RM10 million, possible jail time for those responsible and a damaged reputation can far outweigh the cost of running a proper treatment plant.
| Healthcare Costs | Treating waterborne illnesses is expensive. |
| Environmental Clean-up Costs | Remedying polluted areas is costly. |
| Property Damage | Untreated wastewater damages property. |
| Tourism Loss | Contaminated areas deter tourists, affecting the local economy |
Ajinomoto Malaysia Berhad's Wastewater Treatment Plant
Our factory at the Bandar Enstek Halal Hub, Negeri Sembilan, treats all its wastewater in an on-site Wastewater Treatment Plant (WWTP) before discharge or reuse. In 2026, we kept 100% compliance with effluent discharge requirements, with zero material incidents of non-compliance.
Here's how our treated effluent compares with the Standard A limits:
| Parameter | Standard A limit | 2024 | 2025 | 2026 |
| COD | 80 mg/L | 34.1 | 38.6 | 34.3 |
| BOD | 20 mg/L | 6.2 | 8.5 | 8.2 |
| Ammoniacal nitrogen | 10 mg/L | 1.7 | 1.6 | 2.4 |
| Colour | 100 ADMI | 41.8 | 44.5 | 42.4 |
How Our Plant Keeps Effluent Within Limits
Good results come from checking the water at every step, not just at the outlet:
- Membrane technology in our WWTP separates sludge from treated water.
- Online sensors track pH and dissolved oxygen around the clock.
- Our own lab tests samples from each treatment stage every day.
- An accredited third-party lab verifies the results every month.
- If treated water ever misses the standard, it goes to an emergency holding tank for retreatment instead of the river.
- Our team trains through certification programmes such as CePIETSO, and we review discharge performance in regular Environmental Management System meetings.
Our environmental management system is ISO 14001:2015 certified.
Reusing Treated Water
Clean effluent is too useful to throw away. In 2026, we reused 19.9% of our water from harvested rainwater and treated discharge, mainly for irrigation and our scrubber system. We're working towards recycling 30% of our treated discharge water. We also run a 20 KL rainwater harvesting system.
Turning Sludge into Fertiliser
The sludge from our plant doesn't go to landfill. Specialised contractors turn it into agricultural fertiliser and biofertiliser, one of the ways we apply the circular economy in our operations. It's part of what makes Bandar Enstek a green factory.
Want to see it for yourself? Book a factory visit or call our Customer Care Line at 1800-88-1001.
Frequently Asked Questions
What is industrial wastewater treatment?
It's the process of cleaning water used in factories so it can be safely released into rivers or reused. It removes solids, organic matter, nutrients and germs, usually over three stages. In Malaysia, the treated water must meet limits set by the Environmental Quality (Industrial Effluent) Regulations 2009.
What are the 3 stages of wastewater treatment?
Primary, secondary and tertiary. Primary treatment settles out solids. Secondary treatment uses bacteria to break down dissolved organic matter. Tertiary treatment filters out what's left, removes nutrients such as nitrogen and phosphorus, and disinfects the water.
Why is BOD important in wastewater treatment?
BOD shows how much oxygen microbes will use to break down the organic matter in wastewater. High-BOD water pulls oxygen out of rivers and can suffocate fish. That's why Malaysia caps BOD at 20 mg/L under Standard A and 50 mg/L under Standard B.
What is the difference between Standard A and Standard B in Malaysia?
Standard A applies to factories discharging upstream of drinking water supply intakes, so its limits are stricter. Standard B applies everywhere else. For example, the BOD limit is 20 mg/L under Standard A and 50 mg/L under Standard B.
What is an example of a wastewater treatment plant in Malaysia?
Ajinomoto Malaysia runs an on-site plant at its Bandar Enstek factory in Negeri Sembilan. It uses membrane technology and continuous monitoring, and in 2026 its treated effluent had a COD of 34.3 mg/L against an 80 mg/L Standard A limit.
