aqua

basin

channel

chemical

clean

dam

dirty

disposal

ecology

engineering

environment

facility

fall

filter

filtration

flow

flowing

hazardous

liquid

manufacturing

narrow

overflowing

plant

pollution

pool

process

purification

raw

recyclable

recycle

recycling

reflection

reprocessing

reservoir

river

round

sanitary

secondary

separate

sewage

station

storage

stream

system

technology

treatment

waste

wastewater

water

waterfall