76 quantity of water collected, only 1 million m3 per annum is treated by the purification station due to the fact that some zones are not connected to the sewage network. The technique used is biological lagooning. In the city of Bujumbura, only 38% of the surface area is linked to the public sewage system. At the national level, according to the 2005 MICS survey, 47.6% of the urban population and 30.8% of the rural population has access to healthy excrement evacuation installations, namely 31.7% at the national level. Major provincial disparities nonetheless remain as is indicated in Table 22 below. The rate of healthy excrement evacuation equipment in installation is thus 4 times greater in Muyinga than in Mwaro, Rutana or Bururi. Article 17: The Right to Education 17.2. Free and compulsory Education 17.2.1. Formal Education 17.2.1.1. Primary Education. The objective of primary education is to ensure that by the year 2015 all children, in particular girls, children in difficulty and those who belong to minority ethnic groups, have the possibility of acquiring compulsory, free and quality primary education, and to pursue it up to completion. With the 1973 reform, the Community Schools which had been advocated and the management of which was supposed to have been entrusted to the surrounding community had not succeeded in increasing the pupil intake. In 1981 the Government had actually seriously tackled this problem of access to education and projected the full enrolment for the 1987-1988 school year. The gross enrolment rate increased from 29.3% in 1980-1981 to 72.5% in 1990-1991. Regarding the education of vulnerable children (disabled, orphans, street children, Batwa minorities), 1- to lighten the parents’ burden who today have to shoulder the costs of caretaker, of uniforms and school materials. 2- to balance the educational map.