Every few months there’s a news report about the need to fix the aging water and wastewater infrastructure in cities. To engineer David Sedlak, the future contains more than just the Big Pipe. In his future, solutions will be customized to each situation and onsite technology may play a major role.

Sedlak is a professor of engineering at the University of California-Berkeley, co-director of the Berkeley Water Center and deputy director of the engineering research center for Reinventing the Nation’s Urban Water Infrastructure, a collaborative project involving several universities and funded by the National Science Foundation. The ideas he talks about here are part of his recently published book, Water 4.0.

Pumper: In your book you say water 3.0 was the construction of municipal wastewater treatment plants in the 20th century. Where are we now in the shift to water 4.0?

Sedlak: I think it depends on where you are. We have pieces of the next technologies in place in certain cities, but these revolutions do not happen at the same rate in all places. The front line of change is in cities where the existing systems are unable to serve people’s needs. With respect to urban drainage, you will find the leading edge in cities like Philadelphia and Indianapolis where leaders are working on green infrastructure ­— green roofs and bioswales that absorb water or slow it down.

I have two visions for how this could work out for our water and wastewater systems. One is a central treatment and recycling system. Today those are managed by government. The other vision is distributed technologies built first for clusters of homes in neighborhoods or developments. These could be run by utilities or private companies that contract with government agencies.

I see a possibility for in-house treatment — a membrane bioreactor can treat a home’s wastewater in the space taken up by a modern clothes dryer — but this will require decades to happen. It’s hard to make such a change in one house, just as it’s difficult today to take a single home off the power grid. As time goes on we’ll see retrofits, most likely through a requirement to upgrade at the time of sale.

Pumper: Where does onsite technology fit into what you see?

Sedlak: Green infrastructure is a large civil project, but onsite contractors have skills in plumbing, drainage, excavating and grading. They could have a role in rebuilding or altering urban drainage.

There is also the need to build the next generation of onsite treatment systems. These devices will be better than the septic systems we now rely on because there will be more biotechnology built in. What we’re talking about is extending onsite technology into parts of cities where it doesn’t exist now. The limit to how far this could go is population density. At some point you overwhelm the capacity of the soil to treat effluent, so you have to turn to municipal sewers. With next-generation systems that reuse water for irrigation or for toilets, you can serve a much greater population density before you reach the limits of the soil and groundwater.

Pumper: Do you believe treatment will eventually become the responsibility of the homeowner?

Sedlak: In less densely populated areas, yes. One opportunity for onsite installers will be in the parts of cities that are expanding. It will depend on the costs a developer faces to hook up to sewers and on the capacity of the municipal system to accept the additional flow. Capacity is one reason why we have combined sewer overflows. Cities expanded but did not expand their collections systems for the additional demand. As a result, they suffer when they continue to hook up more homes.

The solution will differ for each location. In many places we will limp along with what we have because changing big systems is very expensive. In some places the geology and soils won’t support extensive onsite systems. And then there is the issue of population density. I don’t see onsite treatment taking off in the core of Manhattan or downtown San Francisco, but many of our cities are quite suburban. If you look at what we have now, when you’re in the country everything is onsite. As you move closer to a city center there is less onsite treatment. I see us pushing the boundary for onsite treatment closer to city centers.

Pumper: What skills should onsite installers develop now so they’re prepared for that future?

Sedlak: It is difficult to know the exact skill set that contractors will need. Certainly installers should maintain their abilities in construction and plumbing. Beyond that I think there will be an advantage to those who know how to work with Internet-enabled sensors and electronic controllers. We will have more sensors and actuators that can be triggered remotely, and we’re already seeing the start of this. Some pump manufacturers are already giving IP addresses [for Internet access] to pump electronics. Eventually an operator will be able to contact those pumps from anywhere and adjust them.

Maintaining the security of these Internet-enabled machines will be important. One problem we have now is people set up machines but don’t upgrade them. To keep these future machines running securely, an onsite installer will have to swap in new circuit boards and upload new software. I don’t mean that they need to be able to write computer code from scratch, but many machines will probably come with a base package installed — as computers do now — and a competitive installer will be able to alter this and add value by providing custom functions or new functions tailored to a specific situation.

Pumper: Where do codes and regulations fit in?

Sedlak: I think the codes and regulations in many cases have not caught up with technology. That’s made worse by not having enough people to enforce the codes, so health officers and building departments fear being given some new requirement or unfunded mandate. Increasing permit fees to cover costs would make permits prohibitively expensive. On top of all this they have to worry about risks to public health. Graywater reuse is suffering from this problem now.

Solving this requires advocates. Michael Nutter, the mayor of Philadelphia, saw green infrastructure as one of his signature approaches and worked for it, and there are other politicians and utility leaders around the country who have made it a priority, but many politicians won’t invest in the issue because they don’t see a payoff. Municipal wastewater utilities long ago learned the need to advocate for themselves, but leadership in the onsite industry is more diffuse. Yet there are possibilities. Many nongovernmental organizations and environmentalists support these ideas, and it makes them natural allies for the onsite industry.

Pumper: In the last sentence of your book, you talk about the need to start changing now before some crisis forces us into poor but necessary decisions. Can we change?

Sedlak: There are times when we have been foresighted enough to lay the groundwork that we need. In the 1990s there was a water supply scare due to a drought in Southern California, and it led to a large investment in securing the water supply. Even though the drought is all over the news now, and the water utilities will not become greatly concerned unless the drought goes on for a few more years. So there is a clear benefit to those who are wise enough to act before a crisis occurs.