Sewage and grey water

Sewag 4

Two different technologies are offered for the treatment of black water (sewage) and grey water (typically from showers, basins, washing machines, car wash and industrial wash water). These are:

  • Submerged fixed-film aerated technology
  • Membrane reactor (MBR) technology

Their use depends on the required quality and application of treated effluent.

Rhino Water's plants are ideally suited for rural communities, temporary camp sites, holiday resorts, service stations, mining facilities, factories, housing developments and smaller municipal waste water treatment plants. The plants are reliable with low maintenance and energy requirements.

Submerged fixed-film aerated technology

Over the last 40 years, submerged fixed-film technology has proven itself to be reliable and cost effective. We have installed, commissioned and operated many successful plants in Africa.

The process uses naturally occurring bacteria and oxygen to reduce the biochemical oxygen demand (BOD) load and facilitate the nitrification and denitrification of ammonia.

The system comprises four stages:

  • Effluent flows via gravity to a collection sump or lifting station.
  • Anaerobic and aerobic treatment, which employs bioreactors.
  • Clarifier where settled sludge is recycled back to the anaerobic phase.
  • Disinfection

Fixed-film systems produce very little sludge. Small quantities collected in the settling tank are returned to the anaerobic phase and broken down into methane gas, carbon dioxide and water. Depending on the volume and BOD influent values, the anaerobic zone (septic tank) will require de-sludging every three to five years.

Our effluent systems are robust with little maintenance requirements. The only moving parts are the pumps which operate automatically. Back-up aeration pumps and off-the-shelf components reduce downtime and enable trouble-free operation in all conditions across Africa.

All our systems are designed to meet the Department of Water Affairs' general standards, applicable to discharge to a water resource.

Plant designs include three options:

  • Concrete systems: Generally for flows exceeding 200 kl/day.
  • Containerised systems: 50 kl/day for 12m containers or 25 kl/day for 6m containers. This option is best suited for short to medium term projects such as construction camps. Modular designs are easily upgradable to meet growing capacity loads, and location-specific demands can be accommodated in every design.
  • Freestanding sewage treatment plants: 1 – 50 kl/day. Chemical grade, UV-protected roto-moulded tanks are used.

Membrane Reactor (MBR) Technology

MBR technology is extremely efficient in treating high organic load effluent, including food process waste, industrial waste water, and effluent containing fats, oils, greases and sewage. Treated effluent complies with the Department of Water Affairs' general standards, applicable to discharge to a water resource, and may be used for irrigation, toilet flush and process wash water.

MBR technology combines membranes separation and conventional activated sludge (CAS) process. While the CAS process uses a secondary clarifier or settlement tank for solid/liquid separation, an MBR uses a membrane for this function, greatly improving solid-liquid separation and producing effluent of a very high quality. Nominal pore size of membranes is typically 0.1 microns and effectively removes all suspended solids and virtually all bacteria and protozoa from the wastewater, resulting in a clarified and disinfected product effluent.

Since the sludge solids are completely retained in the bioreactor, the solids retention time in the bioreactor can be controlled separately from the hydraulic retention time. High sludge concentrations can thus be treated in a much smaller footprint and retention time than with other technologies.

Our bioremediation process is assisted by addition of specific natural bacteria to significantly reduce COD, BOD and suspended solids, and effectively remediate fats, oils and grease as well as petroleum hydrocarbons. Odour control is achieved through breaking down of hydrogen sulphide and complex mercaptans. Real bottom-line savings are achieved by increasing overall efficiency of the plant and reducing sludge removal frequency.