The environmental impact of liquid waste is easy to underestimate, because most of it disappears down a drain or into a tanker. But sewage, grease, oily water and chemical effluent that escape into the environment pollute rivers and wetlands, contaminate groundwater and close beaches. In a water-scarce country like South Africa, every litre that is polluted is a litre lost. This article explains how liquid waste causes harm, what the law requires, and the practical steps homes and businesses can take to reduce their impact.
What counts as liquid waste?
Liquid waste is any waste that flows, from domestic sewage to industrial process water. The main types we deal with in Cape Town are:
- Sewage and septic tank sludge from homes and properties that are not connected to the municipal sewer.
- Grease trap waste, the fats, oils and grease captured from restaurant and food-production kitchens.
- Oily water from oil-water separators at workshops, wash bays, fuel stations and factories.
- Industrial effluent, including process water, wash-down water and liquids that contain chemicals.
- Contaminated stormwater, where spills, wash water or sewage overflows get into the stormwater system.
For a broader introduction, see our guide to liquid waste disposal in Cape Town.
The environmental impact of liquid waste
Polluted rivers, vleis and coastline
Sewage and food waste are rich in nutrients such as nitrogen and phosphorus. When they reach rivers, vleis or estuaries, they feed rapid growth of algae and water plants, a process called eutrophication. When that growth dies back and decomposes, it strips oxygen out of the water and kills fish and other aquatic life. Organic waste also uses up oxygen as it breaks down, so even food waste that seems harmless can suffocate a stream.
Contaminated groundwater
Liquid waste that soaks into the ground does not disappear. Leaking septic tanks, failing soakaways and illegal dumping on open ground can carry pathogens, nitrates and chemicals into groundwater. Cape Town sits on important groundwater resources, including the Cape Flats Aquifer beneath the sandy soils of the Cape Flats, and many properties outside the metro rely on boreholes. Contaminants move quickly through sandy soil.
Risks to public health
Untreated sewage carries bacteria, viruses and parasites that cause stomach and intestinal illness. Sewage that spills into stormwater drains ends up in rivers and at the beach, which is why coastal water quality is monitored and beaches are sometimes closed after a spill.
Blocked sewers and overflows
Fats, oils and grease poured down the sink cool and harden in the pipes, then bind with wet wipes into solid blockages. Blocked sewers overflow from manholes into streets and stormwater systems, and a single kitchen without a working grease trap can cause repeat overflows in its street. Our article on the environmental impact of poorly maintained drains looks at this in more detail.
Oils, fuels and chemicals
Oils and fuels spread across the surface of water, coat wildlife and stop oxygen getting into the water, and many industrial chemicals are toxic to aquatic life even in small amounts. This is why workshops, wash bays and fuel stations use oil-water separators, and why those separators must be emptied and serviced regularly.
Stormwater is not wastewater
One of the most common causes of pollution is liquid waste going into the wrong drain. In Cape Town the stormwater system is separate from the sewer: gutters, street drains and channels carry rainwater straight to rivers, vleis and the sea without treatment. Anything washed into a stormwater drain, whether it is oil from a wash bay, paint from a building site or grease from a kitchen yard, goes directly into the environment. Our guide to sewer drains versus storm drains explains the difference.
What South African law requires
Liquid waste is regulated at national and local level:
- The National Water Act (36 of 1998) makes it an offence to pollute a water resource, and requires anyone whose activities cause or could cause pollution to take reasonable steps to prevent it.
- The National Environmental Management: Waste Act (59 of 2008) sets the framework for how waste is stored, transported and disposed of, and holds the waste generator responsible for it from creation to final disposal.
- Since August 2019, liquid waste may not be disposed of at landfill. See South Africa’s liquid waste landfill ban.
- Municipal by-laws, including the City of Cape Town’s wastewater and industrial effluent by-law, control what businesses may discharge into the sewer and require grease traps and other pre-treatment where needed.
Businesses that produce liquid waste should keep a record of every collection and proof of safe disposal. The details are in our guide to waste disposal compliance requirements.
How to reduce the environmental impact of liquid waste
Reduce it at source
- Scrape plates and pans into the bin before washing, and never pour cooking oil down the drain. Collect used cooking oil for recycling.
- Fix leaks and avoid running water where it is not needed. Less wastewater means less to treat.
- Keep waste streams separate. Mixing oily or chemical waste with ordinary wastewater makes the whole volume harder and more expensive to treat.
Keep grease traps and separators working
Grease traps and oil-water separators only protect the sewer if they are emptied before they fill up, because a full grease trap lets grease straight through. Set a service schedule based on volume (see how often to clean a grease trap) and use a professional grease trap cleaning or oil-water separator servicing provider.
Store liquid waste safely
Keep drums and containers closed, labelled and on bunded surfaces that will contain a spill, away from stormwater drains. Keep a spill kit where oils or chemicals are stored.
Maintain septic systems
A septic tank that is never emptied pushes solids into its soakaway, which then fails and releases partly treated sewage into the ground. Regular septic tank cleaning protects both the system and the groundwater around it.
Use a licensed contractor and keep the paperwork
Liquid waste must be transported by a licensed operator and taken to a permitted facility. Ask for proof of safe disposal for every collection. Drain Blasters is a licensed liquid waste transporter with the City of Cape Town.
A quick liquid waste checklist for businesses
| Question | Why it matters |
|---|---|
| Do you know every liquid waste stream your site produces? | You cannot manage what you have not identified. |
| Is your grease trap or separator serviced on a fixed schedule? | Overflowing interceptors are a leading cause of business-related sewer blockages. |
| Does any wash area or yard drain to stormwater? | Stormwater goes to rivers and the sea untreated. |
| Is your waste collected by a licensed transporter? | You remain responsible for your waste until it is safely disposed of. |
| Do you keep proof of safe disposal? | Inspectors and auditors will ask to see it. |
Liquid waste collection in Cape Town
Drain Blasters collects and transports liquid waste for homes, restaurants and commercial sites across Cape Town, including septic tank waste, grease trap waste and oily water. Find out more about our liquid waste removal service, or read about how liquid waste management keeps drains clear.
