Removing Nitrates and Nitrites from Borehole Water Without Ion Exchange Resins

Are there cheaper and more durable methods of removing Nitrate and Nitrite from borehole water other than ion exchange resins? We are faced with very high concentrations of Nitrate and Nitrite in borehole water, far above permissible limits by WHO guidelines and Nigerian Industrial Standards (NIS) for drinking water. Since Nitrates and Nitrites in drinking water cause the condition, called methemoglobinaemia which causes cyanosis and, at higher concentrations, asphyxia and children are at more risk than adults [Reference: WHO], how can I remove them?  Which technologies can I use to remove Nitrates and Nitrites other than using ion exchange resins?