I would follow the treatment steps generally used in municipal water treatment. Step 1, gravity settling; 2) primary filtration (silk handkerchief or the like; 3) secondary filtration (something like an outdoors water filter); 4) advanced filtration by Granular Activated Carbon or Charcoal (GAC); 5) addition advanced filtration by reverse osmosis; 6) UV disinfection. If you conform to flow rate to treatment time, you should be good to go. Most of this stuff is something you should be able to obtain in a residential capacity module or make yourself. Be aware that water pressure, preferably by manual pumping, will be required for a small upflow GAC tower and reverse osmosis. Municipal water treatment also generally involves coagulants and flocculants, oxidants (flocylic acid, potassium permanganate) and pH adjustment. Don't believe you'll want to try those at home.