글_박규백 신화아쿠아(주) 전무이사

(1) 물속 이물질, 오염물질을 걸러내어 물을 청명하게 한다.

(2) 유해한 병원성 세균 또는 미생물이 증식하지 못하도록 약품 잔류농도를 유지한다.

(3) 물에 독성이나 자극성이 없도록 유지한다.

(4) 물에 불쾌한 냄새나 맛이 없도록 유지한다.

(5) 수영장 물의 온도를 보정하여 일정한 수온을 유지한다.

[표 1] 수영장 수질관리의 기본요소

[그림 1] 크립토스포리듐(와포자충), 출처 : CDC(미국질병통제예방센터

[그림 2] 편모충, 출처: CDS (미국질병통제예방센터)

Water treatment system for swimming pools using perlite

Ⅰ. Introduction

As living standards increase, there has also been an increase in the number of visitors to water parks, spas and swimming pools. Meanwhile, the public’s understanding of water treatment used in swimming pools is still lacking, leading to mistrust and confusion. While it may be difficult for all laymen to understand water treatment, providing basic information on it to visitors of swimming pools form an important part of the obligation and customer service of pool operators. It can also help in improving customer satisfaction and promotion.

A few years ago, a news article on swimming pools brought much anger among the public. At the time, a lawmaker in the Council for Environment and Labor in the National Assembly had the data on swimming pools analyzed. It showed that swimming pools only changed their water every 30 days on average. The lawmaker’s opinion was that “the time and effort required is the reason for infrequent change of the water in swimming pools.” But this was turned into a sensational headline, “Swimming pools run by Seoul City neglects to change water to save money.” The article prompted many citizens to add angry comments online.

Of course, there may be some swimming pools that do not meet the standards for water quality or facilities, leading to fines or customer dissatisfaction. But the main reason for infrequent water change is not simply about ‘saving money’.

It is true that current law does not stipulate the frequency or number of times for water change in swimming pools. But the standards for water quality are stipulated, including an obligation to have all the water pass through a filter at least three times a day and have the water be under a certain level in terms of the concentration of residual chlorine, hydrogen ions, turbidity, potassium permanganate, bacteria,  arsenic, mercury and aluminum. Under the law, water that meets these criteria is considered clean water and therefore does not need to be changed. Given that the local government samples the water at least monthly to review the water quality and facilities and the swimming pool operators themselves conduct water quality tests, it is not correct to say that not changing the water equates to a neglect in water quality management. Changing all the water in a swimming pool not only costs money for the water but time to refill. If we assume all the water is switched once a week, it would be impossible to operate the swimming pool normally. 

It is the area where the highest level of consumption occurs that there is the greatest room for cost savings. If swimming pools that consume a large amount of water can conserve, not only would it save costs, but it would also help them live up to their social responsibility of conserving energy and the environment.

Ⅱ. Perlite Media Filtering

1. Overview of water treatment in swimming pools 

The main objective of water treatment in swimming pools is to maintain the water in a safe and pleasant state to swim in. This objective can be further broken down into the following.

(1) To clarify the water by filtering out foreign matter and pollutants in the water.

(2) To maintain a certain level of the concentration of treatment chemicals to prevent the growth of harmful bacteria or pathogens.

(3) To maintain the water in a state free of toxicity or irritability. 

(4) To maintain the water in a state free of unpleasant odor or taste. 

(5) To maintain the water at a certain temperature

[Table 1] Basic elements of water quality management in swimming pools

　　　　　　　　　　유량 및 순환량: Quantity of water flow and circulation

　　　　　　　　　　시수의 희석: Dilution of the water

　　　　　　　　　　여과장치: Filtering device

　　　　　　　　　　소독 및 pH조절: Sterilization and pH control

Turbidity of water is most important when discussing water quality in swimming pools, not only in terms of hygiene but safety of the visitors. If the water is not clear, it can obstruct the view of swimmers leading to injuries. It also makes it difficult for safety guards to identify injured people. A key factor in maintaining good water quality is the filtering device. If the water treatment device is inadequate, it is impossible to achieve a desirable water quality. 

Foreign matter in the water are reported to negatively affect the sterilization system. Floating matter in the form of small particles can act as a protective shield for bacteria, obstructing the sterilization, or react with specific organic matter in the water to generate harmful compounds (Swimming and Spa Water Treatment 2012, published by Lovibond Water Testing). Filtering devices are very important in removing parasites such as Cryptosporidium, flagellates and their larvae that are not removed by chlorine.

[Image 1] Cryptosporidium, Source: US CDC 

Cryptosporidium can be removed by a filter of 4 ㎛ or finer, while flagellates can be removed by a filter of 7㎛ or finer (Lange et al.,1986). But the porosity of regular multi-layered filters are 30㎛~100㎛, making them insufficient to filter out such infectious bacteria.

[Image 2] Flagellates, Source: US CDC 

Studies published in the World Aquatic Health Conference showed that the Perlite Filter removes an average of 99 percent or more of Cryptosporidium (waposporium) under stable pre-coat conditions. To be exact, 99.941% removal was reported on average, while multilayered filters which is the most widely used filtering machines in the worldwide removes 31.3% Cryptosporidium on average. The addition of chemicals(coagulant) to multilayer filters improves its performance, but even under the improved filtration conditions the Cryptosporidium removal rate remains only at 61.1% (Source: Athletic Business. Paul Steinbach). 2008)