Wastewater treatment for recycling application is usually done at the tertiary treatment step, with the primary principle is based on the membrane filtration process.
Depending on the recycling purpose and required treated effluent, Koastal Eco will determine which type of membrane is applied.
Hereunder is the technical specification of membranes applied in the wastewater recycling process.
MICROFILTRATION (MF) AND ULTRAFILTRATION (UF)
MF and UF filters are used to separate suspended solids and suspensions from water by membrane technology with a pore size of about 20nm – 5µm under low pressure. This filtration system acts as a safety step for the following RO filter system (if applicable). A common application of this membrane is MBR technology (see also the section in Biological treatment process and Advanced treatment process).
Applications in recycling: treated effluent can be reused for road cleaning, car washing, landscape irrigation, toilet flushing.
The current recycling of water in Vietnam is often applied to only a part of the capacity of the wastewater treatment plant due to cost restrictions. The size of the UF Koastal Eco system used for water reuse is 25 m3/h.
NANOFILTRATION (NF) AND REVERSE OSMOSIS (RO)
NF and RO filters are often used to remove bacteria, low molecular weight organic compounds, and ions in water (NF filters are more limited than RO filters in their ability to remove mono- atoms.). The process is implemented using the membrane technology with a pore size of about 0.1nm – 1nm under high pressure. When using the NF or RO filtration system, a prior coarse filtration system is required to remove large solids first, to reduce the frequency of clogging and membrane washing.
The water quality after the NF and RO membrane filtration systems is very high. Thus, this filter system is often chosen as a reuse solution for projects that require high-quality water after treatment such as water technology for some industries and even for drinking water.