How to create single lines from a plain text field with line breaks
I've made a little macro for this:

{% macro splitText(text) %}
  {% set text = text|nl2br|raw %}
  {% set text = '&lt;span class="split_text"&gt;' ~ text|replace('&lt;br /&gt;', '&lt;/span&gt; &lt;span class="split_text"&gt;') ~ '&lt;/span&gt;' %}
  {{ text|raw }}
{% endmacro %}


You may need to tweak it a bit, but this is what worked for me.