"But the multinational company would rather you not call them swimming pools." There's a reason for that. If they were swimming pools, then they would have to meet commercial/public state regulatory standards for disinfection and water quality. These are more akin to
Natural Swimming Pools (NSPs) (which are really more like ponds) from a regulatory point of view which means they will not be held to the same bacteriological standard as swimming pools.
Their
patent #7,820,055 has a simple summary of the following:
The present invention is related to a process to obtain large water bodies or volumes (wherein the term obtaining is meant to be understood as implementation and maintenance), wherein a structure is provided (having elements required for water treatment and features that produce the desired results) to contain the water, and separation and flocculation (maintenance) processes of particles that make water cloudy and impure are performed, in such a way that flocculated material is suctioned by a suction device once flocculation has taken place, and oily materials are removed through skimmers (surface slots or dumps) of the structure of the present invention, said structure having pipes that feed fresh water to fulfill the desired objective.
More specific detail is the following that describes the individual steps:
The process of the invention comprises the following steps or stages:
a.--providing a structure with skimmers able to contain a large water body larger than 15,000 m.sup.3.
b.--feeding the structure of step (a) with inlet water having iron and manganese levels lower than 1.5 ppm and turbidity lower than 5 NTU.
c.--measuring water pH, ideally it should be within a range lower than 7.8;
d.--adding an oxidizing agent to the water contained in the structure of step (a), with which a 600 mV minimal ROP is controlled in water for a minimal period of 4 hours and in maximal cycles of 48 hours;
e.--adding a flocculating agent in concentrations within 0.02 and 1 ppm with maximal frequencies of 6 days and cleaning the bottom of the structure of step (a) with a suction device to remove precipitated impurities from the bottom of said structure, together with the additional flocculants and;
f.--generating a displacement of surface water containing impurities and surface oils by means of the injection of inlet water according to step (b), which generates said displacement in such a way to remove said surface water by means of a system for impurities and surface oils removal arranged in the structure of step (a).
Note from the following that they depend on mostly complete water replacement (constant exchange) so need to be near a large body of water such as an ocean or lake:
In the disclosed structure or lake in step (a) it should be maintained a minimal total water renewal rate of 150 days, preferably 60 days, to avoid the accumulation of oxidation products (ageing).
They pre-filter the water if necessary to get the turbidity below 5 NTU. Note that this is not crystal clear water and would have a Secchi disk (alternating black and white sections) be not visible at a depth of around 2.5 feet. Obviously their additional flocculation steps are used to improve from this initial water clarity and this pre-filtering is just to get rid of the bulk of particulate matter in rather turbid water. They also reduce iron and magnesium to below 1.5 ppm, presumably to prevent colored water and staining.
If the incoming water has a pH higher than 7.8, then they add sodium bromide (unless the water already contains it) so later oxidizers will essentially create bromine. Presumably this is because bromine will remain more effective than chlorine at higher pH.
They maintain a minimum 600 mV ORP for at least 4 hours every 48 (preferably 24) hours by adding oxidizers such as ozone, sodium or potassium persulfate, chlorine derivatives, hydrogen peroxide, bromine derivatives or by electrochlorination. They say the levels needed for this 600 mV ORP are the following: USUAL OXIDANT CONCENTRATION * MIN-MAX RANGE Ozone 0.05 ppm 0.01-0.58 ppm Hydrogen peroxide 0.04 ppm 0.01-0.46 ppm Sodium hypochlorite 0.16 ppm 0.04-1.50 ppm Persulfate 0.28 ppm 0.07-3.30 ppm Bromines 0.22 ppm 0.05-1.80 ppm. In fact, I calculate that if they actually used 0.16 ppm FC they would have closer to 710 mV ORP. To get to 600 mV ORP one would only need 0.005 ppm FC. So I suspect that the oxidizers fairly quickly react with bromide to form bromine so a higher bromine level (0.36 ppm total bromine) is needed to achieve the 600 mV ORP. I wonder how without a lot of circulation they are able to get to this ORP throughout the lagoon.
They use a flocculating agent and have a suction device at the bottom of the lagoon and they have skimmers at the top for removing oils. The entire lake is cleaned every 7 days, preferably every 4 days.
In addition to using cationic polymers for flocculation, they can also use algaecides including Polyquat or copper where the latter would be between 0.3 and 1.5 ppm for usual 10ºC (50ºF) to 30ºC (86ºF) water temperature.
So this is NOT a large swimming pool in that it does not consistently have a disinfectant and when it does disinfect it is not at the minimum levels for swimming pools. It is not designed to prevent person-to-person transmission of disease except for the large dilution effect given the large body of water. The bather load in such a large lagoon or artificial lake is fairly low.
The news article stated the following:
Instead of common pool equipment, the company builds its gigantic Caribbean beach replicas with technology that somehow uses ultrasound for purification. Water quality is monitored and adjusted remotely from a control center. Beyond that, little is known publicly about the patented technology. But these exports are clearing regulatory hurdles here in the U.S.
Note that "ultrasound" is not mentioned in the patent at all so I don't know where the news article is getting such information. The
Crystal Lagoons website doesn't mention ultrasound, though does mention remote monitoring.
