TDS and pH in Drinking Water

Water is a very important need for life. Not only for hygiene needs, water is also consumed by the body to meet the mineral needs needed by the body. Based on the general aspect, good drinking water is colorless, odorless and tasteless. However, there are important parameters that must be measured to determine the quality of drinking water consumed.

In the process, drinking water can be produced using 2 types of water, namely surface water and subsurface water. The process carried out on water also depends on the water source used. In this case, each company must have a different water purification system, but in general the process is carried out as follows:

1. Sedimentation/ flocculation

This stage is the stage of clumping (coagulation) of small particles contained in the water source so as to form a larger particle so that it is easy to filter later. For the formation of this coagulant / flocculant requires additional substances in the form of aluminum salts or ferric salts.

2. Filtering

At this stage, the water that has been taken from the source is filtered using several materials and several filtering steps. This filtering step can consist of filter, pre-filter and final filter. The purpose of this stage is to remove fine impurities and harmful ions present in the source water. The materials used are sand (sand filter), ion exchange filter and activated carbon. At this stage it is possible for the processed water to be more easily disinfected.

3. Sterilization

This process is the stage of eliminating microorganisms such as bacteria, viruses, fungi and others. At this stage, ozone is applied to treated water which is intended to kill bacteria, viruses and microbes present in the water or better known as the ozonation process. In addition, some companies still use chlorine as a disinfectant. This stage can also be done by irradiating UV lamps.

4. Shelter

At this stage the water that has been disinfected is accommodated into the reservoir. Distribution of water into the bottle via four pumps. Inside each pump there is a 0.45µm diameter filter which functions to filter all organic matter and microorganisms present in the water after the ozonation process.

Based on SNI 01-355-2006, bottled drinking water is divided into two classes, namely mineral water and demineralized water. Several test parameters that must be carried out on bottled drinking water are shown in Table 1

Table 1. Some Test Parameters for Bottled Drinking Water

No	Parameter	Unit	Condition
			Mineral water	Air Demineral
1	Circumstances
	1.1 Construction	–	No smell	No smell
	1.2 Flavor		Normal	Normal
	1.3 Color	Unit Pt-Co	Max. 5	Max. 5
2	pH	–	6,0 – 8,5	5,0 – 7,5
3	turbidity	NTU	Max.1,5	Max. 1.5
4	Solute	mg/L	Max.500	Max.10
5	Total Organic Carbon	mg/L	–	Max. 0.5
6	Organic Substances (KMnO4 Number)	mg/L	Max. 45	–

Some of these parameters are very important to be tested in the manufacture of bottled drinking water, one of which is pH. From Table 1, it is stated that good drinking water has a pH that ranges from 6 to 8.5. This is disclosed by the World Health Organization (WHO) that if drinking water is consumed too alkaline (pH> 8.5) it can cause irritation to the eyes, skin and tissues and even experience gastrointestinal disorders. On the other hand, if the pH is too acidic (pH<4), the same thing will happen. This is of course dangerous, so bottled drinking water is processed in such a way that the contaminants in it can be minimized and safe for consumption.

Several ways to increase the pH value are by adding calcium or magnesium carbonate (CaCO3 or MgCO3). This addition can be done on pH monitoring before entering the disinfection stage. This is because pH has an important role in the process of disinfection of microorganisms. The use of calcium or magnesium carbonate not only to raise the pH but also to enrich the healthy minerals in the water.

In addition to pH, the parameter that must be monitored is Total Dissolved solid (TDS) or total dissolved substance. If the pH range for good drinking water is in the range of 6.0 – 8.5, it is different with the TDS parameter which should not exceed 500 ppm. This is because the TDS parameter also represents the minerals contained in the water. These minerals can be classified into 2, namely those that are harmful such as arsenic, sulfate, bromide, manganese and others and those that are good for the body such as calcium and magnesium. The TDS value must be monitored because this parameter will affect the taste of the water consumed. However, the high value of TDS will cause damage to systems such as pipes and reservoirs as well as turbines. This is because TDS can cause scale on the system.

Table 2. TDS Value on Water Quality

TDS value (ppm)	Water quality
Less than 300	Very good
300 – 600	Good
600 – 900	Rate
900 – 1200	Bad
Above 1200	Not accepted (very bad)

In the process of monitoring these two parameters, a tool is needed that can meet the needs of the range for drinking water applications, easy to use and very flexible to be brought to the field or for laboratory checking scale.