What evidence in the excerpt supports Schwartz's claim?

Reliably ensuring safe drinking water to the general public is a vital role of local and state govts. Across the US, govt. officials and public water system managers are discovering means to ensure water security. One technique for increasing public drinking water safety which has got the notice of water officials and the general public is reverting treated waste-water to the drinking water supply.

As California struggles for techniques to cope with its severe drought and the obligatory water limitations imposed, an assortment of ideas which were long let go as controversial, unpleasant, or expensive are getting a second look. One is conserving more water, another is turning to nearby and copious water sources such as the Pacific Ocean into drinking water via desalination, and another is to re-cycle the water citizens have used. And there lies a marketing problem which can be greater than a technological problem.

Water re-cycling is common for uses such as delivering water to golf courses, farms, and zoos and for irrigation purposes. At a grass-root level, activists urge residents to save water from showers, bathroom sinks, washing machines, and tubs to water their gardens and plants. The procedures at Orange County comprise microfiltration which eliminates whatever greater than 0.2 microns, eradicating all suspended solids, protozoa and bacteria.

After which is reverse osmosis that comprise pushing the water across a membrane that eradicates other impurities, as well as pharmaceuticals, dissolved minerals, and viruses. A zap with strong ultraviolet light and little hydrogen peroxide cleanses further and neutralises other small chemical compounds. Alluring people to drink re-cycled water, nevertheless, necessitates getting over what specialists refer to as the ‘yuck’ factor.

From a marketing viewpoint, utilising treated sewage to generate drinking water is a proposal which has proved challenging to sell to consumers. The inevitable prudishness over drinking water which was once waste disregards an essential fact, that when it comes down to it, water is water, and everybody who lives downstream on a river is drinking re-cycled water.

taking into account that a theme is the central topic a text treats and can be developed through a story, play, poem etc. the following are themes that can be further developed:  

my best friend jeffrey has many unusual interests. (the story could be about each of the unususal interests)

once a man gives his soul over to evil, he can never go back. (this could be a saying or a proverb)

the three sheepdogs lay around the yard all day. (it could be developed detailing how each of these sheepdogs lay around)

a priest's collar has an unusual effect upon people. (it could be developed detailing the different effect upon people)

innocence is a powerful force in a world full of corruption. (it could be developed detailing how is a world full of corruption)

king lear is a play shakespeare wrote later. (it is just a sentence and doesnt give any idea or topic to be discussed in details.

evil often wears the disguise of innocence. (this could be a saying or a proverb)