Question: Regarding the stench at Kawainui Stream (808ne.ws/kline1020), could Genki balls help, like in the Ala Wai Canal? They’ve got to do something. It smells bad.

Answer: The state Department of Land and Natural Resources’ Division of Forestry and Wildlife is exploring this method of bioremediation to reduce foul odors from rotting organic material at Hamakua Marsh Wildlife Sanctuary in Kailua, said DLNR spokesperson Dan Dennison. However there’s “nothing concrete” about a Genki ball drop to report at the moment, he said.

You are one of several readers to suggest that Genki balls be tossed into stagnant streams or canals along the Kailua wetland, to control the sulfuric stench that worsens as submerged plant life decomposes after heavy rain or runoff. Any such effort would have to be systematic and sustained, as the website for the Ala Wai Canal project explains, genkialawai.org/the-project.

Bioremediation uses living microorganisms to remove pollutants from water and soil. In Genki balls, EM1-brand solution containing lactic acid bacteria, yeast and phototrophic bacteria is mixed with clay soil, rice bran, molasses and water and shaped into balls. Once tossed into the canal, the mud balls sink into sludge at the bottom, where the bacteria they contain go to work. “After Genki balls embed into the surface of sludge, the fermentative bacteria begin to digest and oxygenate the sludge. At the same time, the phototrophic bacteria consume harmful gases, and contain foul odors,” the website says. The goal is to restore the Ala Wai Canal to swimmable conditions, but it will take many, many ball drops to accomplish.

Another reader recalled a demonstration project the DLNR conducted several years ago with Oceanit Inc., which involved installing a temporary siphon to divert water from Kawainui Marsh into Kawainui/Hamakua Stream, restoring some of the flow that had been cut off when the flood-control levee was raised. Given the success of that project, the DLNR should install a permanent siphon “to keep the stream from being stagnant, maintain oxygen levels and protect the wildlife,” he said.

However, Dennison said the siphon project is on hold. “In order to get the necessary amount of flow, it would require major changes to the structure of the levee. The U.S. Army Corps, which provides regulatory oversight of the levee, was not enthused about that idea. So we are exploring other alternatives,” one of which is Genki balls, he said in an email.

To read about the siphon demonstration project, go to kailuawaterways.com and click on “Kawai Nui Flow Restoration Experiment Final Report” in the Reports section.

Q: Regarding short-term rentals (808ne.ws/sty1024), what’s the registration deadline?

A: “There is no deadline to register. However, owners and operators who do not have an NUC cannot begin renting for less than 30 days until they are registered,” according to Honolulu County’s Department of Planning and Permitting, which answers this and other questions about regulations for Oahu vacation rentals at honolulu.gov/dpp/permitting/short-term-rentals.

NUC stands for nonconforming use certificate, as issued to certain Oahu vacation rental properties in the 1980s that are allowed to operate despite not being zoned for hotel use. NUC holders do not need to register under the new registration system for short-term rentals, but they must renew their NUC in 2022 as usual and annually thereafter to continue operating, according to the DPP website.

Annual renewal will be a change for NUC holders, who previously renewed every other year, on even-­numbered years, it says.

Write to Kokua Line at Honolulu Star-Advertiser, 500 Ala Moana Blvd., Suite 7-500, Honolulu, HI 96813; call 808-529-4773; or email kokualine@staradvertiser.com.