An integrated solution for sewage and truck wash wastewater treatment provided by HWT, through which biodegradable wastewater is treated biologically and opportunities for water reuse are created. With a design flow of 10 m³ per day, domestic sewage and high-COD truck wash wastewater are combined within a compact polytank treatment system.
A low-energy biological process was employed, through which organic pollutants are broken down and dissolved nitrogen compounds are removed. Furthermore, opportunities for reduced operational carbon emissions can be explored through efficient equipment selection and renewable electricity supply.
How Sewage and Truck Wash Wastewater Treatment Is Carried Out
Initially, sewage and truck wash wastewater are conveyed by gravity to a pump sump arrangement, which is included in the scope of supply. The incoming pipe invert is positioned 2.4 metres below natural ground level, allowing wastewater from the upstream drainage system to be received.
The blended wastewater is then pumped to the biological treatment plant. Treatment is carried out in a series of four 10,000-litre polytanks, providing a total nominal tank capacity of 40,000 litres.
Before the biological stages, coarse solids are intercepted by a washable Dragon Sock screen. Consequently, downstream equipment is protected and the quantity of unwanted solids entering the treatment process is reduced.
Biological Treatment and Foam Control
Within the biological treatment stages, biodegradable organic material is broken down by microorganisms. In addition, dissolved nitrogen compounds are removed through the biological process.
Foam control is provided to support operation where foaming is encountered. However, the suitability of the blended feed must be confirmed against the actual wastewater characteristics. In particular, detergents, oils, grease and any substances that could inhibit biological activity should be assessed when the final design is developed.
Disinfection and Treated-Water Measurement
Following biological treatment and solids separation, chlorine disinfection is applied in proportion to the treated effluent flow. As a result, the disinfectant dose is adjusted as the discharge rate changes.
Treated effluent flow is also measured, allowing plant throughput to be monitored and records of treated-water production to be maintained.
Opportunities for Water Reuse
Once the required quality has been achieved, treated water can be considered for irrigation, toilet flushing, dust suppression and fire-water storage. Environmental discharge may also be considered, subject to the applicable requirements and authorisations.
The plant is designed to achieve the DWS General Limits, subject to the agreed influent design conditions and correct operation. Nevertheless, suitability for each reuse application must be assessed separately, since additional quality requirements may apply.
Further information is provided in the DWS General and Special Limits.
Automated Operation in a Compact Arrangement
Plant operation is automated so that routine manual intervention is minimised. Nevertheless, screening, chemical replenishment, inspection and maintenance are required to sustain reliable performance.
Poytank installation in the eastern cape
