iirc you donw need a $1 behind alias like in rewrite-rules

http://nginx.org/en/docs/http/ngx_http_core_module.html#alias

the following should work

location /wifi {
alias /var/www/owums/public; # <-- be sure to point to 'public'!
passenger_base_uri /wifi;
passenger_app_root /var/www/owums;
passenger_document_root /var/www/owums/public;
passenger_enabled on;
passenger_app_env development;
}