Dumai Drinking water plant from surface water

Sustainable proposition

What if organic micro pollutants, nano plastics, turbidity, humic acid (natural organic matter), viruses and bacteria can be removed in a single stage filtration step?

While achieving an unimaginable level of carbon footprint reduction compared to traditional treatment methods? NX Filtration has accomplished just that, and has the full scale commercial references in operation around the world to prove it.

Showcasing its strengths as promised: superior water quality at lower cost and lower environmental footprint!

Based on full scale operating data from a municipal surface water treatment plant, City of Dumai (Indonesia), with hollow fiber nanofiltration membrane technology. This Project not only shows real operational data from almost two years of operation of a 180 m3/hour hollow fiber nanofiltration membrane drinking water plant, demonstrating an OPEX of $0.19 per m3 of water produced, which is not only a savings of 15%, but also a huge reduction of 85% in chemical dosing compared to the neighbouring conventional system.

The Challenge
Due to increased urban population, the city has planned to increase the city water supply, which requires approximately 40,000 m3 of potable water per day, in three phases, with the first phase being approx. 4,000m3/day. In the tropical geography of the location, the city relies on the turbid- and peat rich Mesjid River as the source of potable water. Removing humic acid, a known trihalomethane (a carcinogen which is generated when feedwater with high organic concentration is chlorinated) precursor, was, therefore, a key issue.

Humic acid concentration is indirectly represented with color, which is in the range of 800 to 1,100 TCU. According to the regulation of the Indonesian Ministry of Health, the color content of drinking water should be no greater than 15 TCU. In addition, the turbidity of Mesjid River is in the range of 5 to 100 NTU, which should be no greater than 5 NTU for drinking water. Both for turbidity and color, the city’s existing water treatment system with conventional flocculation + clarification, could not meet these requirements.

Figure: Full operational system in Dumai – 2 years of successful operation
The Solution
In September 2019, the city conducted a pilot study to test the breakthrough hollow fiber nanofiltration membranes side by side with tight hollow fiber ultrafiltration (UF) membranes. The UF membrane was tested as a polishing treatment after the existing conventional treatment with an additional media filter step. Although the product water quality improved significant after the UF, it still was not possible to achieve a quality meeting the drinking water standards consistently.
On the other hand, NX Filtration’s direct nanofiltration (dNF) membrane does not require media prefiltration nor pre-treatment chemicals since its nominal MWCO is 800 Dalton*, which can effectively remove humic acid in its native form.

(*dNF membrane with MWCO 400 Dalton is also available depending on application.)
The results
The dNF membrane treats the Mesjid River water directly with just a generic strainer prior to the membrane filtration step. The results were remarkable. Permeate of dNF membrane stably exhibited below detection limit for both color and turbidity. While permeate of UF showed similar result for turbidity, however, it barely met the regulation for color. It should be noted that color and turbidity of dNF permeate was not dependent on feed concentration fluctuation, which indicates that dNF was a perfect barrier for color and turbidity in this particular site.

Moreover, operational cost of the dNF membrane system was less than a half compared to the conventional treatment process, which could not achieve the required treated water quality. The additional cost required for dNF membrane replacement and the slightly higher electric power usage were much lower than the chemical cost required for the conventional process, which requires coagulant such as PAC as well as a polymer flocculant. It should be noted that sludge treatment cost of the clarification was not even taken into account in this cost comparison, where dNF does not produce any sludge waste stream.

Regarding the system footprint, the Dumai City was able to utilize existing property which was reserved for media filtration. The city did not consider spiral would NF membrane system after UF pre-treatment as an option, however, if it was adopted, the required footprint would have been larger than the originally proposed site, and
installation and operational cost would have been significantly higher than for the dNF technology. The investment for this project was partially financed by the World Bank.

Figure: 2 trains of 25 lps each, with NX Filtration WMC200 dNF80 modules

The first phase plant with >4,000m3/day capacity was commissioned in April 2021 and since then, it has been in stable operation till now. The detailed operating data of the plant is shown in Table 1.

Table. Detailed OPEX Cost vs. Conventional treatment

The long-term operating data of the plant is shown in the figure below. The data shows the transmembrane pressure (TMP) and the product water flux of the train. Although there is a strong variation in the feedwater quality and the pretreatment to the membranes system is limited, the operating performance is very stable.

Figure: 2 Long term operating data of the 2 trains of 25 lps with WMC200 dNF80 modules

The figure below provides a general representation of the complexity of traditional water treatment processes, either with chemicals (coagulation) and/or conventional membrane systems (UF and spiral wound NF or RO). When direct nanofiltration is selected the treatment train can be significantly simplified.
Figure: Robust and sustainable process replaces a complex and expensive train of technologies
Proven results from full scale operation
• Superior water quality
• No sludge from coagulants and flocculants
• 50% saving on Opex
• 85% saving on chemicals
• Low energy consumption of 0.3 kWh/m3


Robert Gerard
Water and wastewater expert